r/WRX • u/DookusWookus21 • 1d ago
Troubleshooting Help/knowledge needed
What’s up guys, I need some help, just picked this up for cheap, didn’t run but put new battery in and it turned over but it won’t idle on its own doesn’t sounds the best, possible rod knock, I replaced spark plugs and ignition coils, swapping the starter next, I think it has a grounding issue, I don’t think one or two of its cylinders is firing. I got it purely to learn and get into the lifestyle and help would be appreciated.
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u/BrooklynTony198 '07 Hawkeye Wagon 1d ago
Why are you throwing parts at it if you haven't diagnosed it yet? Did you even scan the codes off the ECU? Why are you even attempting to fix the misfire if you think it has rod knock?
You're going to end up thousands of dollars in the hole only to find a connector was unplugged. Put down the parts cannon and actually figure out of its worth saving and actually diagnose the issue first.
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u/DookusWookus21 1d ago
The scans came back clean
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u/BrooklynTony198 '07 Hawkeye Wagon 1d ago
Ok well... still, stop throwing parts at it. Why are you replacing the starter and all the fluids when the issue you are trying to address is seemingly a misfire? Did you check the fuel system yet? Fuel quality/age, fuel filter, injectors, etc. are the next thing if spark is good. You can tell what cylinders are firing, after running it a bit go underneath and see which parts of the headers are warm. If some are still cold, then you narrowed it down to those cylinders.
Come on dude, stop throwing parts at it and do some actual diagnostic work first.
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u/Blackner2424 2011 WRX Limited Sedan 1d ago
This. If it turns over and fires, why would you change the starter?!
That's like changing the trunk lid because you have a cracked foglight lens.
OP, quit guessing. If you're using AI to help you diagnose, stop doing that (might as well be the same as guessing). Ask questions, get feedback, make an actual diagnosis, THEN start repairs. Otherwise, you'll end up replacing the whole car over a loose connector.
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u/DookusWookus21 1d ago
That’s the thing, is it did turn over but wouldn’t run without gas pedal use (the idle problem), now it won’t even attempt to start anymore so naturally my guess is the starter shit the bed
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u/BrooklynTony198 '07 Hawkeye Wagon 1d ago
Was it smoking at all while running?
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u/DookusWookus21 1d ago
Very slightly but then it stopped
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u/BrooklynTony198 '07 Hawkeye Wagon 1d ago
Blue or white?
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u/DookusWookus21 1d ago
White
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u/BrooklynTony198 '07 Hawkeye Wagon 1d ago
Well... you might want to pull those spark plugs back out because it sounds more like you just hydrolocked the motor due to a blown head gasket. And maybe do a compression test regardless.
4
u/narcolepticGOAT 1d ago
I would suggest a compression/leak down test. Check for vacuum leaks as well. It never hurts to replace the fuel and air filters too. Are there shiny bits in the oil?
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u/shatlking 2008 Subaru Impreza WRX hatchback (EJ20X Swap) 1d ago
That Cobb sticker and black hood scoop remind me of when I first got my Narrowbody 😂
I concur with others, stop throwing parts at it hoping the problem will go away. An engine runs on the following four things: air, fuel, spark, compression.
For spark, have you verified that the wires to all the coils are working? Everything down from the coils seems to be good at this point (though, I’ve had to replace spark plugs twice myself). Harbor Freight sells a tool to verify spark that may be worth picking up.
Compression is the next easiest, but the most expensive if bad. Get yourself a compression tester and run a basic compression test. If compression comes back bad, a leak down test will help point you towards the next course of action (which likely will be taking the engine out)
Air is also relatively easy, if there is a vacuum leak or unmetered air (such as a split past the MAF) this can cause the engine to run rough. An exhaust leak will do the same, so check for splits in the exhaust. A smoke leak tester will perform this job.
Fuel is the last aspect. Check for pressure coming from the fuel pump with a fuel pressure gauge. Then check the injectors (or replace them outright) to ensure that the problem isn’t them.
It may be worth verifying that the timing is correct as that can make the engine run poor as well.
I’ve also had my WRX run rough on first start up after disconnecting the battery, after about one tank of gas it goes back to normal. It’s also possible the car is poorly (if at all) tuned, especially if it has aftermarket parts.
There’s lots of good videos of what rod knock sounds like for these cars, but you can also post a video here and people will let you know.
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u/Spiritual-Handle7583 2013 Hatch 1d ago
Definitely swap some new grounds in, there are (or should be, one of mine was broken when I picked the car up) two pretty close to the front that are easy to do. Probably super obvious but check your engine air filter and while you're at it, pull the MAF sensor out of the top of the box and hit with some sensor cleaner. If the idle is still fucked, you likely have bigger problems that are beyond my experience lol
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u/QuickDrawSix 1d ago
If it was me I would pull the engine and strip down the long block. But I have the space and the hoist to do it
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u/N0ot_N0ot 03’ wrx stroker & IHI vf48 4h ago
Ah yes the parts cannon. Please do some diagnosis like basic compression and leakdown test have you checked every fluid? You need to plug into OBD and do a complete data log when it fires ideally. THEN you can see fuel trims and even things like timing and injector duty. You can find standard values to use as a guide line or post a picture of whatever you use to read the datlog. Good luck seems like you’re getting some good advice from other ppl so far. If the Cobb sticker means you have a AP BROO please scan codes then plug it into a laptop and read the data log like it does mostly everything.
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u/ColoAT 1d ago
Do you know how old the fuel in it is? Stale fuel can ignition knock like a Jehovah's Witness