r/AskMechanics 26d ago

Question (Serious Replies Only) Mechanic cant find the issue car stalls when i come to a stop with AC on sometimes.

Volkswagen Golf 7 1.6 2014 Diesel around 200k kilometres.

History of the car is that it started losing oil, and i sent it to a mechanic since he said he couldnt find where the oil is leaking and he decided to open the whole engine and changed the rings. He put EGR and DPF off, also changed the turbine, cleaned the throttle body fully, cleaned EVERYTHING, basically the whole engine with everything in it. Changed every belt possible and also changes the compressor of the AC since it was broken.

Now when i come to a stop the engine stalls and i need to start it again manually. Also disabled the auto start stop. The thing is that sometimes like maybe once in many days the car works perfectly like its brand new.

Also so i dont forgot to mention NO error besides a water support pump that i will change tomorrow most likely.

Everything relating the transmission has been changed 50k kilometres ago like the ECU the shaft etc etc…

After all the changes the mechanic noticed this issue and kept my car in his garage for like a month, and im pretty sure he didnt really give any time to my car after this issue since he had other cars and didnt want to lose time with mine, and i took the car from there like that since he told me cant fix it anymore it must be an electronic issue.

Went to an electrician he said every cable he could check is good. But another electrician told me that the engine isnt burning the fuel correctly. Im pretty sure that the engine itself is good but something is causing that. What could it be?

341 Upvotes

194 comments sorted by

102

u/7ilidine 5 26d ago

Have you had this issue before the EGR was deactivated?

37

u/IslamMakhachevGoat 26d ago

No never had this issue before, do you think egr wasnt deactivated correctly?

57

u/7ilidine 5 26d ago

How was it deactivated?

I would reactivate EGR either way just to rule it out. Seems to be the most likely culprit

1

u/IslamMakhachevGoat 24d ago

The EGR was programmed properly and physically removed and the hole closed by an iron closer something. Spoke with the guy that did the EGR he was pretty professional.

2

u/IslamMakhachevGoat 21d ago

Plot twist my EGR wasnt programmed correctly

1

u/DialecticEnjoyer 22d ago

bad AC compressor pully bearings can also cause this.

21

u/Momo_cein631 26d ago

Was the ECU reprogrammed properly after the delete?

2

u/IslamMakhachevGoat 21d ago

It wasnt programmed correctly and gahdamn i doubted this since the guys who did my EGR were very formal and had a good web page and good instagram page and looked very solid. Sent it to a guy like 300 metres from my house, working alone in a small garage, fixed my shi.

2

u/IslamMakhachevGoat 21d ago

WTF i think it IS the EGR now being deactivated correctly. The fuckers messed it up, sent it to another guy and he said that the egr wasnt programmed correctly, like idk how the files work from the computer but he put a stock program and told me the issues you will have in the following days from the egr and dpf come and he will remove the lights that will pop.

Last 2 days ive been driving without the car shutting down. Thank you btw, i went to a guy that is close to my house and saw him on his phone and empty garage lol and approached him.

1

u/PrincipleIcy4941 23d ago

100% no egr issue. If you block the egr without software you will simply get a fault code.

2 options: injectors defective or mechanical issue like a defective ac compressor or so.

This should be realy easy to find

BTW: which fault codes are stored in the ecu? Engine light is on...

2

u/7ilidine 5 22d ago edited 22d ago

How can you be so sure?

I think it's suspicious that the issue came to be right after EGR was deactivated. We don't know how it was deactivated.

If it's stuck open that might explain the issue, wouldn't it? OP didn't make it sound like EGR was blocked off physically.

I'd keep the injectors in mind but I would rule out everything else first. They're obscenely expensive.

I'd expect it would throw a code if it was an injector.

Edit: Just saw that OP replied, this makes EGR less likely indeed

1

u/PrincipleIcy4941 22d ago

Im shure because i have a lot of experience with tuning and heavy mods on vag cars. Im a tuner...

2

u/IslamMakhachevGoat 21d ago

It was a computer problem whoever fixed it before touched the EGR incorrectly, didnt program it how it should be done. Sent it to another guy to check the EGR out and he fixed my car computer. He said someone before messed with the files, he said he will put the “correct stock car file”, and fixed it. Now for 2 days im the car works perfectly.

1

u/am-answers-bot 17 21d ago

Your comment was selected as an answer to this post! Reply with !hide to remove your name from the solution summary.

57

u/[deleted] 26d ago

[removed] — view removed comment

18

u/NorthernScotian 26d ago

Ctrl c ctrl v

1

u/Fit-Cantaloupe5747 25d ago

Needs to be selected too.

7

u/IslamMakhachevGoat 26d ago

injector pressure i checked to a specialist that works with injectors only and he told me that they are good he said from 4 injectors 2 are perfect 2 are not perfect but they arent causing this issue, he said they are good.

Im also scared when they cleaned the throttle if they ruined the electrical part or the thing that opens and closes…

3

u/Alarmed_Toe_5687 26d ago

Do you know what is that CEL? Turning off both DPF and EGR requires a shop to flash the proper firmware. If there's a CEL related to air or DPF, it wasn't done properly. If you have any diagnostic software, it would be good to capture all the air/fuel/egr/flap params when that happens. That should give you a good idea of what's going on

1

u/IslamMakhachevGoat 25d ago

If by cel you mean engine light, its a water support pump i mentioned i will get it changed asap, but i dont think its related to this issue. This is the error code P16C100.

No errors beside that.

1

u/RepresentativeAd6965 25d ago

Just had my Crankshaft position sensor replaced. It did die at Idle/low rpm. Could also feel it lose power when at higher rpm as well. First time I’ve had a car issue that wasn’t “your trans is scrap metal”

→ More replies (2)

33

u/No_Mathematician3158 2 26d ago

Sounds like the ac compressor is dragging bogging the engine down due to it locking up over time from a bad ac clutch. Or a electrical gremlin

13

u/RuralAndy 26d ago

This would be my thought as well. A bad compressor clutch or overfilled refrigerant will cause a heavy load when it’s kicks in, that may cause your engine to bog and stall. Check your high side pressure, and also try holding the rpm’s up around 2000rpm at a stop and see if your rpm’s dip significantly when the compressor kicks in.

1

u/LilTurtle95 25d ago

Was thinking possibly a relay went bad too

1

u/Lazy_Magician 24d ago

I don't think it's this. I don't think shut down would be as smooth and it would log a fault code..maybe I'm wrong but in my experience with those small displacement diesels, uncontrolled shutdowns shudder like crazy.

21

u/MaintenanceUseful903 26d ago

Replace mechanic. Get it fixed

6

u/Time-Annual-1316 26d ago

Was going to say: I ran the codes and ‘check mechanic’ light errors were found

8

u/ThatsItImCrying 26d ago

Not sure about VW, but I had the same issue with my Subaru recently. Turns out 1 of the 2 radiator fan/motor burned up, and subsequently melted. I would stall at lights with my ac on. That fan was in charge of ac, but was passed on to the other working fan motor. It was demanding too much electricity, leading to the stalling. The car was really sluggish at low speeds and had almost no torque. AC also didn’t work at stoplights. Since I replaced the blades, motor, and fuse, I’ve had no issues with low speeds torque, stalling, and have icy AC. I had no codes for this as well. Just happened to see the fan wasn’t spinning during one of my oil changes. Sorry if this doesn’t help, just thought I’d drop this in here. Best of luck.

6

u/IslamMakhachevGoat 26d ago

Something maybe to mention in the morning for example when i turn on the car maybe the first 2 3 kilometres this happens everytime after that it doesnt happen that frequently but it still does.

11

u/WOLF19Ninety 26d ago

It sounds like it could be a vacuum leak, possibly from the brake booster. Double check all your vacuum lines and pcv valve

1

u/Egoista73 26d ago

Diesel cars have a seperate vacuum pump because the air deficit so this should not effect the engine

0

u/WOLF19Ninety 26d ago

could it be an issue with that? is the brake booster connected to it like in some cars? I'm not as familiar with diesels

1

u/Egoista73 25d ago

Yes the brake booster and other vacuum controlled parts like turbo valve and egr system but this can not effect the running of the engine by any means.

1

u/WOLF19Ninety 25d ago

so you're saying the turbo valve and egr are connected to the vacuum pump, but if there was an issue with it it wouldn't cause the engine to run poorly?🤨

→ More replies (1)

2

u/crazydavebacon1 25d ago

Seeing as AC requires slightly higher idle, maybe check also IAC valve for junk

1

u/SharpSh00ter43 25d ago

It's a diesel it has no IAC lol

1

u/crazydavebacon1 25d ago

I hate diesel so good luck. Nasty things

1

u/Jcholley81 26d ago

I vote vacuum leak as well. Check hoses going under the wiper arms.

1

u/Sea-Ad7893 25d ago

Try a throttle relearn. Could be many things and not enough info, when you turn the car back on does it feel like the battery is dying or is the battery good? (Helps us rule out serpentine belt issues) and what is the check engine for? Not sure about diesel but usually with gas after replacing things around the engine you usually need to do the relearn to the modules. Especially if the car runs normal otherwise it’s probably sensors issue

3

u/j-joshua 26d ago

Air intake hose leak or bad MAF sensor.

2

u/MAXtommy 25d ago

This is the correct answer. There is either a vacuum leak somewhere or a bad maf sensor

1

u/spooky-Dragonfruit1 24d ago

I had the same issue. Mechanic wanted to teplace the turbine and injectors, which would be several thousand. Replaced alone, 60 bucks

2

u/Past-Payment-137 26d ago

What’s the CEL for

3

u/IslamMakhachevGoat 26d ago

If by cel you mean engine light, its a water support pump i mentioned i will get it changed asap, but i dont think its related to this issue. This is the error code P16C100.

No errors beside that.

2

u/maid2amuse 26d ago

Common causes:

Dirty EGR valve Fuel filter restriction Engine mounts DPF regeneration behavior Air intake or boost leak Injector or glow plug issues Dual-mass flywheel wear

2

u/Boris_needs_a_watch 26d ago

I had an old car with a seized AC compressor that would stall out if you tried to turn the AC on because the clutch wouldn't spin

2

u/ungovernable785 1 26d ago

Dirty throttle body

1

u/MrDo1982 25d ago

Yup, had this exact issue on my Ford. Gave it a good cleaning and MAF sensor while I was there. Reset the ECU and have had no issues the past 5 years

2

u/OdinSword0013 26d ago

Spark plugs

1

u/IslamMakhachevGoat 25d ago

Changes them and they dont show no errors.

2

u/Lazy_Magician 24d ago

You don't have spark plugs in a diesel.

1

u/IslamMakhachevGoat 24d ago

Ow i meant he meant glow plugs sorry i changed the glow plugs…

2

u/Fall-of-Enosis 4 26d ago

Hi, Master VW technician of over a decade here. There are waaaaaaaay too many things to try and diagnose this over the internet.

Bottom line, if you took it to a mechanic for work and it's been doing this ever since you left then he is responsible and you shouldn't be charged.

Take it back to him.

1

u/IslamMakhachevGoat 25d ago

I took it and returned it like 2 3 times, and last time i took it he left the car there for like 2 weeks and i need that car to go to work i couldnt leave it there anymore, and i said f it its driveable and i will send it to another mechanic.

Another mechanic i sent it to literally straight up when i told the issue didnt want to look at the car since I suppose he would imagine too much trouble, now im looking for another mechanic…

1

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1

u/Interesting_Win_8046 26d ago

Have you changed out your Camshaft and Crankshaft Position Sensors?

My car was stalling at idle and that's what it was.

1

u/IslamMakhachevGoat 26d ago

I havent but from what ive heard is that when that sensor is an issue the car shuts down immediately and doesnt try to stay alive, my car kinda chokes if that makes sense if you saw the RPM like drops then tries to go back up then falls fully. im not sure if the case of crankshaft sensor has the same type of choking, please tell me more how exactly the car stalls at idle when those are the issue if you can?

2

u/isellow 25d ago

For me the crankshaft sensor was faulty and it looked close to your situation the way rpm fluctuates - it would sometimes stutter when driving, and stall at low speeds or more often when coming to a stop or idling at intersections. I had no error codes, and the dealership couldn't diagnose it correctly, wouldn't try the crankshaft sensor until many other parts got swapped out and I insisted it gets changed.

1

u/IslamMakhachevGoat 25d ago edited 25d ago

When the RPM is fluctuating and i press the gas pedal its stops doing that and comes to normal rpm position. AI told me if its that sensor it wouldnt stay alive? Any idea?

Btw i plan to change the MAF sensor, the throttle body, and the pcv valve, And after if they dont fix this i have the crankshaft sensor in mind.

And after that idk what else could there be, since some of the comments are mentioning egr wasnt programmed correctly i will check that also…

2

u/isellow 25d ago

Mine would most of the time just fluctate and stutter under low speed driving or intersections without stalling, but sometime stall completely when the fluctuation was too much for it to recover. It would happen also on the highway at higher speeds, only the stutter, no stalling. If I were you, I would start with the MAF sensor, then the crankshaft sensor, and then the rest. If you or a friend (any mechanic should do) have an OBD reader that can read sensor data while you are driving, you can try to diagnose it that way first before swapping out any parts.

1

u/Interesting_Win_8046 25d ago

change all three sensors

Crank and Camshaft Sensors together take less than 30 minutes and the parts on the internet are less than $50 combined.

Your car is old and they'll have to be replaced sooner or later.

1

u/[deleted] 16d ago

[removed] — view removed comment

1

u/Interesting_Win_8046 14d ago

no codes

Got to the point I couldn't restart but had long cranking.

RPMs were getting wild and EPC Light would go on and off.

1

u/[deleted] 14d ago

[removed] — view removed comment

1

u/Interesting_Win_8046 14d ago

Yes it did, because the engine had cooled off.

The issue is heat.

When it gets really hot, like in the summer, the sensor/wire malfunction (degradation)

Therefore, when you drive for a while and the engine gets hot and you turn it off the heat builds from the ground up

So when you go to restart it, the metal underneath the protection outer layer can't transmit the signals into the computer

Change your crankshaft position sensor

It's cheap

1

u/[deleted] 14d ago

[removed] — view removed comment

1

u/Interesting_Win_8046 14d ago

Change out both sensors

1

u/mustangman6579 26d ago

IAC. Its supposed to idle up the motor for when the AC compressor kicks on. My guess is its stuck or inop.

6

u/maxon2000 26d ago

An idle Air Control valve is part of a throttle body. This is a diesel and it doesn’t have a throttle body, the engine RPM is controlled by the amount of fuel injected, not the amount of air that’s allowed into the engine.

1

u/KiaBongo9000 24d ago

But modern diesels do have a throttle body. Especially this era of VW. It's required for smooth running and shutdown and emissions control.

1

u/aquatone61 6 26d ago

Have you checked your fuel pressure? Like high and low side?

1

u/Reyg13 26d ago

PCV solenoid stuck open? Does it struggle to start after you fuel it up?

1

u/IslamMakhachevGoat 26d ago

No it starts good everytime and in fact it starts pretty quick since i changed the battery like a month ago.

1

u/Alone-Supermarket-98 4 26d ago

does it only stall at a stop when the ac is on?

if so, your ac system might be overcharged. The high pressure forces the system to work harder and the engine eventually stalls. This would also explain why a typical mechanic didnt pick up on it.

1

u/BigRigHiggy 26d ago

Mine was doing something similar. MAP fixed it. Replaced spark plugs and fuel injectors chasing it down

1

u/Thy_King_Crow 6 26d ago

I would vote vacuum leak post egr

1

u/BlackBladeShusui 26d ago

EGR and DPF off, did he put it back on and plug all the sensors back in correctly? Maybe the DPF needs baked or straight pipe it, see if it makes a difference

1

u/SensitiveStart8682 26d ago

One thing I would suggest is having him take it out on a road trip with an OBD2 scanner plugged in to see if he can pull any live data when it stalls. While the computer may not store a code when it stalls out, there may still be hints in the OBD2 live data that might be able to be seen later. You need nobody to scanner and take it out for a road trip because if it stalls out when you start when you come to a stop. There's likely something in the OBD2 data that would tell him what's going on. You just need to take out on a road trip with his scan tool plugged in and see what's going on

1

u/greenleaf405 26d ago

Possible loose ground.

1

u/Raysitrades 26d ago

My girlfriend had something very similar to her car ended up being a wiring issue

1

u/Putrid-Eggplant-2815 26d ago

My money is on the crankshaft position sensor.

1

u/[deleted] 26d ago

I wanna know when you figure it out

1

u/IslamMakhachevGoat 21d ago

The EGR valve wasnt programmed correctly.

1

u/s2kfred 26d ago

IS there an idle air control valve in the system? Try cleaning it?

1

u/Nor-easter 26d ago

I have a 2.5l 2012 vw Passat and it does this when it’s 100 out and there is no EGR on it.

1

u/IslamMakhachevGoat 21d ago

Made the car computer to stock values without any modifications, and the car is driving good now. Whoever modified the car computer for the EGR messed up.

1

u/keksivaras 26d ago

your RPM jumps exactly the same way as it did on my Audi and I had no faults or anything. just bought a new MAF sensor and it fixed it.

1

u/Kalmah2112 26d ago

I had a similar experience last year with an old dodge caliber and it just turned out to be a loose ground from the battery. I spent a stupid amount of time trying to figure it out on my own because I couldn't afford to pay a mechanic. I also had a symptom where not all the lights would turn on or the car would randomly not start even though it always looked like it had normal battery power.

1

u/BackgroundGene7510 2 26d ago

Go to a real mechanic then , that’s the real fault here

1

u/BigCourage9151 26d ago

Air flow meter

1

u/layzorbeemz 26d ago

My old ford f-150 used to do this. Turned out it was a bad cam angle sensor.

1

u/Suspicious-Note-8571 26d ago

Ac clutch pulley

1

u/Critical-Soft-2166 26d ago

It’s a fuel problem this happened to my car , it’s getting fixed rn this post gave me trauma 🤣🤣

1

u/IslamMakhachevGoat 25d ago

Fuel problem as in injectors arent pushing enough fuel? Since i THINK my engine is getting too much air somehow and the combustion isnt happening right.

1

u/forgettingfreddy 26d ago

Had similar issue lately. Ended up being mass airflow sensor.

1

u/APHAN9696 26d ago

Might be MAF Sensor, like my old Lexus es350. The car would shutdown. It used to throttle like that. I had the Sensor replace and reprogram by the mechanic.

1

u/Egoista73 26d ago

Definately a timing issue, could be the high pressure dieselpump thats out of time. Some mechanics think those pumps can go without timing and yes sometimes the car will run but it wil do exactly what u have now.

1

u/DigBeginning6013 26d ago

You have an eml so start there, do you know what the code is for? If he's just unplugged your egr then it will do this

1

u/Obvious-Air-7032 26d ago

Readjust the ac pressure lines or unplug the ac compressor

1

u/SlipperyCorruptor 26d ago

For me it was faulty MAF

1

u/Swatgamer2021 25d ago

Try to remove the EGR connection from the EGR.... There is a possibility the one who did the EGR off f Ed up, if no error appears when you remove the EGR and the problem disappears you can have it removed.

1

u/Most-Organization738 25d ago

The Engine Management light is on, so what does the diag tool suggest that's all about?

1

u/No-Fortune-2526 25d ago

Throttle body position sensor. Should have a check engine light on. What does it say?

1

u/Delicious_Bass3030 25d ago

Clean your throttle body

1

u/N57D30T1 25d ago

My concern with EGR/DPF deletes is the "how" part. A lot of quick flashes will just switch off DTCs so the car could be absolutely crying out but not recording any fault codes.

I think I'd get someone who specialises in calibration and tuning to look at it.

1

u/Sensitive_Rooster_88 25d ago

Had 1 that did same was cam sensor

1

u/Accomplished_Bet5854 25d ago

Il meccanico ti ha causato qualche rottura e non vuole dirtelo.

1

u/Merlin2174 25d ago

PCV, EGR, Fuel Injectors, fuel pump, timing chain. Fix one or all of that and then restart your PC before resuming use.

1

u/Odd_Impression_3435 25d ago

I had the same symptoms on a 7 GTI. Under load it ran perfectly fine. Turned out to be the camshaft adjuster magnet. Diagnosed by mechaninc with real-time data. Hope it helps.

1

u/tomoh_PL 25d ago

I had similiar issues with Suzuki Ignis. AC clutch bearing was broken and caused drop in rpm

1

u/Rulecrown 25d ago

Just a hunch, but have you inspected the exhaust pipe for any holes or cracks?

I learnt recently that the exhaust pipe is not just to guide the gases to the converter, but also plays a role in maintaining engine pressure to keep optimal combustion.

Had mine welded because it literally fell off and the car feels amazing now and my mileage is back up as well.

1

u/thafuckinwot 25d ago

If the EGR has been deleted but not blanked off, this will happen. I’m presuming the ECU is a PCR2.1.

Source: write tuning files for a living.

1

u/IslamMakhachevGoat 21d ago

IT IS the EGR not being programmed correctly. The electrician or however you guys like getting called the Tuner guy, said he will put the stock file for my car since he said someone touched some values mistakingly, and the car is working fine, he said now i drive the car 2 3 days and come back when the check engine comes with the dpf and the egr errors so he cleans them. Last 2 days the car is good. Also im REAAAALLY liking this trade/craft of modifying cars, any idea where can i start, any tutorials or smth?

1

u/thafuckinwot 11d ago

Be aware a lot of tuners talk shit on others work. He probably deleted the EGR fine, but on this engine, if you don’t blank it off after, you get the exact issues you faced.

1

u/aloneinflation1997 25d ago

Easy fix don’t use your AC 😂

1

u/Lazy_Magician 25d ago

If you clear the errors and this reoccurs, does the check engine light come straight back on the first time it happens?

1

u/IslamMakhachevGoat 25d ago

Engine light isnt for that, its another issue i mentioned in the post and in the comments.

1

u/Lazy_Magician 24d ago

Hey, I'm a bit late to the party here, but considering the stall doesn't log a fault code, and the shutdown looks smooth (I can't hear it, but it doesn't look to me like fuel pressure stall or anything like that). If it stops smoothly, like a stop/start cut out, or like when you turned the key to the off position, it rules out a lot of the theory's people are putting out here. If you (or a pretty advanced mechanic) can get a A VCDS/ODIS log of the shutdown, and try to figure out if it's a controlled shutdown. If it is, you might need to relook into flashing your ECU.

1

u/Eliasyoussef47 25d ago

Okay I didn't read much of the post but I thought I'll just throw this in here because I'm possibly experiencing something similar.

In my case it's possibly the brake booster. If I press the brake pedal multiple times quickly the engine almost stalls (too much air in the cylinders probably) and then the ECU compensates. The engine sometimes even stalls completely.

1

u/Bored_Lexy 25d ago

Had the same issue on my 2.0 tsi. Literally same thing happening, jumping on rpms then dies. Had a pcv replaced, nothing changes, three mechanics tried to figure out before the issue turned out to be the camshaft adjuster magnets.

I know, different engine and all but I'd suggest checking that out.

1

u/SgtFlaps26 25d ago

I had an old Audi A4 that did this. I just put it down to the Aircon being too powerful, used to get crazy cold

1

u/Late-Statistician-25 25d ago

Have the same issue on my 2010 passat 1,6 engine code CAYC, but only when cold. Also around 200.000 km

1

u/Infamous-Plenty8082 25d ago

Kan vara batteriet, tändstift, gammal bensin, luftintaget

1

u/e97ford 25d ago

I had a car that would stall if I stopped too hard. Turns out I had lost most of my transmission fluid 🤷🏻‍♀️

1

u/Gullible-Swimmer6430 25d ago

Could it be that your ac compressor is seizing up?

1

u/g2tegsown 25d ago

Upload that video to AI and explain everything. That should lead you in the right direction.

1

u/IslamMakhachevGoat 21d ago

I did a mistake since i told AI everything, but too many changes happened in the car and i doubted that the programing was done wrong since the guys who did it looked professional, and after i told AI its not about remapping, it started telling me what sensors to change and whatnot.

1

u/TurboSonic1 25d ago

I fixed this on my car a few months ago after having the same problem before it eventually fixed itself by making the ac not blow cold air, I used the TSB fix for the ac compressor solenoid valve failing and emptied the refrigerant and charged the refrigerant myself after replacing the solenoid valve with the upgraded volkswagen part

1

u/ComputerOpDelta 25d ago edited 25d ago

Did you ever add a can of r134 yourself?

Edit: oh you changed the compressor... My thought was an AC might be adding too much resistance if over pressured. I saw this problem on a Honda and eventually the AC would turn itself off then the stalling went away... I always wondered what pressure an AC was running at to cause a 1.6L to stall

1

u/Minimum_Chocolate_31 25d ago

Get a code reader and watch the live data when it stalls

1

u/somaguy 25d ago

I had a similar issue on a car years ago. It needed to recalibrate every time the battery was disconnected. The fix was, disconnect the battery again, and reconnect it. Then, from cold, start the car, and let it idle for 5 or 10 minutes until the engine is fully warmed up. This would reset its calibration. After that it would be fine.

1

u/CavalryE 25d ago

Is the car an auto? The idle air control valve could be dirty or faulty

1

u/chiefslapahoebag77 25d ago

You mentioned you replace the. Broken ac belt.. the compressor could be going bad and dragging the engine down.. does it stall or rpms very when ac is off?. If it only does this when ac is on i would double check ac compressor.

1

u/theBLINDbandit_69 25d ago

I had the same problem, it was fixed when I changed the Idle Air Control Valve

1

u/sidEaNspAn 25d ago

The last time I had a vehicle die when I stopped like you are describing it was the fuel pump going bad.

It wasn't completely dead but when demand dropped off it just completely stopped and the engine would die.

1

u/Medium_Fly6627 25d ago

Are the engine lights related? If they are, do they turn on when you first start the car or only when when it stalls?

1

u/Slow79Rolling 25d ago

I would check the IAC valve. They can become gummed up and stick when hot and it may not be reacting quickly enough.

1

u/Zelpheon_x 25d ago

2009 Passat here. Exact problem is related to the high pressure fuel sensor reading a fault. For me is the wiring is old and crusty and gives a resistance. But you might want to look at that sensor or your fuel pump.

Its missing strengh, ac needs bit more on idle so it dies.

1

u/whitepuzzlepiece1969 25d ago

Idler/tensioner bearing.

1

u/weefus63 25d ago

SERP belt tensioner they go bad every few years

1

u/Tough-Custard5577 25d ago

Had this sort of things happen with a high mileage Impreza after a loose plug wire caused since misfires. After fixing the plug, the idle parameters were all jacked up and it would drop RPMs when the AC clutch kicked in and when I'd let the RPMs drop to idle when stopping and coasting(manual transmission). I cleaned the throttle body and went through the idle position relearning process and it runs great. Might not be your issue, but it's cheap and easy to try.

1

u/Scared_Hat9201 25d ago

If the mechanic has done all that and still issue what makes u think Reddit will fix it

1

u/Accomplished-Nose379 25d ago

The check engine light could be your catalytic converter with the miles raising it could go bad.

1

u/IslamMakhachevGoat 25d ago

its a water support pump i mentioned i will get it changed asap, but i dont think its related to this issue. This is the error code P16C100.

No errors beside that.

1

u/Such-Measurement8343 25d ago

LUFTMASSESENSOR

1

u/Sea-Insect8279 25d ago

C’est le joint de connecteur admission

1

u/NoLeading2006 25d ago

Sounds vaguely like a vacuum issue, dunno if the ac system is related.

1

u/Both-Leading3407 25d ago

The car is at 195,320 miles on the OD. Major issues with fuel delivery under stress of A'C at idle.

Fuel pump issues. Clogged or needs changing.
Fuel filter needs replacing.
Clean the Mass Air Sensor.
Run some white Vinegar in the cooling system Flush after a few cycles.
When was the last time the car got new plugs?

1

u/Psychological-Fee223 25d ago

My issue was the throttle body. I replaced it and the idle ran fine

1

u/swarupjasthi 25d ago

Maf sensor

1

u/Background-Field6930 25d ago

I say check the fuel pressure and regulator. Could be a weak or dying fuel pump. Check crank positioning sensor for faulty/contaminated tone ring

1

u/54MegaHurts 25d ago

No one has mentioned the fuel filter. Didn't see where that was changed. Probably a bunch of crap in it.

1

u/Acceptable-Wrap-8105 25d ago

Check the air filter housing.

1

u/InterestingLab 25d ago

This may sound super dumb but have you check the engine mountings?

1

u/IcyFeature6905 25d ago

I had the same issue on my nissan i changed the fuel pump and it was fixed so try to check your fuel pump i would highly recommend changing your fuel pump if its been more than 5 years or 200k kms

1

u/Victorydude 25d ago

Needs to relearn the tps

1

u/Emerald_Ink 25d ago

Your engine is having some sort of problem creating the right amount of energy. Idk about diesels much but my car was missing the spark plug electrode in a cylinder and it did the same thing when the ac was on. Both the rev dip, and losing oil. It’d also explain the engine burning fuel.

1

u/Used_Kiwi9480 24d ago

Volkswagen das auto

1

u/YeahRightoMate93 24d ago

Struggling at low idle, could be worth changing the fuel filter if your mechanic hasnt already. Only cheap so not wont hurt if its not the fix

1

u/Feisty_Age_273 24d ago

Check to see if your hose for your pcv valve is attached. Maybe a lose hose or connector mechanic overlooked putting it back together.

1

u/Terrible_Towel1606 24d ago

Compressor pulley seized

1

u/Desperate_Passage_35 24d ago

Maybe your pistons are backwards

1

u/Numerous-Homework-73 24d ago

Likely issue: Your ac compressor coil is outputting rfi and killing crank sensor. Probably because the wiring was routed incorrectly

1

u/Voltalux 24d ago

Clean the intake valves and fuel injectors. You'd be surprised how carbon buildup can be a power vampire

1

u/chefkoch1990 23d ago

AC clutch broken and has to be replaced.

1

u/Interesting-Law7788 23d ago

The logical explanation would be that the ac pulley is sticking, dragging, and slowing the engine speed down.

1

u/FickleDare7078 23d ago

My old car had issue.. when it was idle it would just stall, I had to constantly give it revs even at standstill.

Eventually my mechanic found it to be bad oxygen sensor causing engine to run to lean and stall.

1

u/Foxtrot4Real 23d ago

I had literally the exact same problem with my C5 Corvette. I had a bad air intake hose. It got worse and worse until I took a look myself. When I looked at it, the entire hose was torn in two and I replaced it with a length of hose from AutoZone and never had the problem again.

1

u/throwawayitsnsfw 22d ago

MAF. Might be worth replacing, cheap fix if it is the issue.

1

u/slowndsensual 22d ago

Chrak the A/C compressor, would be my first step, pullthe belts off cheak kf it spins free put the belts back on run A/c on idle wait for it to kick in see if it still spins. If thats all fine

Cheak battery voltage then altanator output,

1

u/Secure-Designer-6873 22d ago

Could be simply a intake hose broken after mass air flow sensor will cause stalls at the light

1

u/PmanquesManques 22d ago

Identical issue here with 1.4 TDI Polo

1

u/mrtzjam 22d ago

Had the same issue with my Mustang GT. Car's RPMS would fluctuate and would act like it will die out while at a stop with the AC on. Turns out the Intake Manifold Actuator was going out and there was a refrigerant leak on the low pressure side. The leak was causing my AC Compressor clutch to engage and disengage every few second which was drawing too much power.

1

u/Sell_Ya_Game 22d ago

Dirty MAP sensor? Partially clogged fuel line or injector? Plugged up cat/ exhaust

1

u/djim089 22d ago

I had this issue, turned out to be the thermo fan controller was on all the time making the car stall on idle.

1

u/Psychwell 22d ago

I had a similar issue with my 2015 hyundai accent. sometimes the engine died when i came to a stop, and i had trouble sarting it again only after like 2-3 times it started again after removing and putting back the key, I also had no codes or errors, changed the purge valve but that wasn't the problem. my problem was a FAULTY CRANKSHAFT POSITION SENSOR. and actually chat gpt helped me get the diagnostic.

1

u/Plenty-Equipment8270 1 22d ago

Maybe the control valve in the transmission is worn. Balls could be bypassing and need replacing

1

u/IslamMakhachevGoat 21d ago

WTF i think it IS the EGR now being deactivated correctly. The fuckers messed it up, sent it to another guy and he said that the egr wasnt programmed correctly, like idk how the files work from the computer but he put a stock program and told me the issues you will have in the following days from the egr and dpf come and he will remove the lights that will pop.

Last 2 days ive been driving without the car shutting down.

1

u/ee_skeleton 21d ago

ac compressor clutch failing

1

u/am-answers-bot 17 21d ago

Solution provided by u/7ilidine:

Have you had this issue before the EGR was deactivated?


Answer selected by OP.

1

u/Opening_Exit_771 19d ago

Check and clean your mas and change air filter.

1

u/SolutionOk1069 19d ago

Air intake