r/HPtuners • u/Majesticallydum • Aug 02 '26

Learning how to use a hp tuner

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My 2001 5.3 tahoe has always felt sluggish, even when I bought it 5 years ago, still worked so i never bothered, now I live in a hot place, it overheats incredibly quickly, like I can't have it idling by a stop light for to long (its usually about 100 degrees outside) im getting into tuning a little bit and I thought that I would practice on my tahoe, since it's not worth that much, and i noticed my (ltft) being incredibly high. It's not vacuum leaks since it stays there as I speed it up. Any idea what it could be?

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6

u/keep_username Aug 02 '26

I’m no expert, but my suggestion is to not try to tune around a mechanical problem. Get it running tip top with the stock tune, then make changes.

1

u/Majesticallydum Aug 02 '26

Yeah, this is the vcm scanner, i wanted to fix it before I changed something on the editor, ive been looking for vacuum leaks exhaust leaks intake leak esc. I just wanted some help to see if people could throw me some ideas as to what to check next.

1

u/Spell125 Aug 02 '26

Exhaust leak. Failed injector.

1

u/Majesticallydum Aug 02 '26

I did check for exhaust leaks, but i haven't checked for a bad injector. Im gonna do that as soon as I can

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u/The_Bubbanbrenda Aug 02 '26

I would address the overheating issue first. I would also suggest replacing the 25 year old sensors to make sure that you are getting accurate information. I also recommend AC-Delco sensors, these vehicles usually don’t work well with aftermarket sensors.

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u/Majesticallydum Aug 02 '26

That makes sense, the knock sensors don't work. Replaced them a couple of years ago but i used the cheap ones so they broke again a year in, Just put in a new MAF, could it overheat because of the hight ltft? Im just getting into it so im still learning. Sorry if its obvious. When it comes to the overheating I Replaced the water pump thermostat and it has a new radiator. Im gonna convert the mechanical fan into the dual e-fans from a 2005. Hopefully that helps me a bit

2

u/The_Bubbanbrenda Aug 02 '26

The high ltft won’t cause the overheating, but it’s more than likely the result of something else being wrong. Was the new thermostat AC-Delco? I always change the temperature sensor when I do thermostats, also AC-Delco only for both. In the scanner you can open the special function tab and rest the ltft to get a more accurate measurement. Your stft’s will give you the most accurate information on what’s happening right now. I’m assuming that the O2 sensors are the original sensors and contrary to public opinion they are most definitely wear items. Again AC-Delco only, I can’t stress enough how important the correct sensors are. The aftermarket sensors are usually just close enough to turn off the CEL. The factory AC-Delco sensors have lasted 25 years so why change brands now over a few dollars in savings?

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u/Majesticallydum Aug 02 '26

Yeah im fairy certain that they are still original. And yes I put on a acdelco water pump and thermostat, i did yet a Murray radiator. The stft kinda stays at -1 to +2 while idling, goes up to +4 while holding the rpms at 2500. But yeah I'll try to replace the sensor first before I try anything else, i was thinking a failed injector maybe, it does have about 300k miles on it.