Reduced engine power...what causes this? Tune?

[STALKER]

Originally Posted by San2cci

Some more updating....swapping the throttle position sensor did not solve the issue. It eventually returned. The next thing I did was replaced my accelerator pedal assembly. This also did nothing for me. At this point I returned my car back to the stock tune, and it still eventually went into the reduced engine mode. I brought it to Chevy and they ran some tests and said the wiring is fine and suggested I replace my throttle body. They wanted close to $700 for this so I just picked my car up and ordered an OEM AC Delco throttle body through advanced auto. Had a $50 off coupon so it cost about $180 shipped to my house. I'm reusing the throttle body gasket as it is in great condition. These do not come with the new throttle body and cost about $15. Replacing the throttle body is very simple. I'll update in a few weeks, hoping the new throttle body will correct the issue.

Lol...Dealer wanted 700 bucks for a 200 dollar part and a 10 minute swap

This may sound dumb, but I had the same thing happen after my build and its probably worth mentioning, even if its not the reason or fix to your problem:

Are you by any chance having issues with your Tire Pressure Sensors? Reason I ask, because when I originally did my Z28 wheels, I didn't run TPS sensors with them. First time out with the car, as soon as I laid into the accelerator aggressively---- reduced engine power mode - Stabilitrak light - ABS light - etc.

Long story short, it all ended up being because the computer could not detect the TPS Sensors, even though I was getting the same code you were. Good luck!

[San2cci]

That's very interesting. I do have stock rims and TPMS sensors. Different tires but same size as stock. When I removed the stock throttle body I realized the plate was not fully closed. I have to push on it for it to fully close. I believe these should be in a fully closed state. When holding it up to the light I could see about 1/8" gap around throttle plate. Wondering if this could be causing my issue. Just not sure because this only occasionally occurs. I can go 50+ miles without it happening. I'll be replacing the new throttle body tomorrow so only time will tell!

[CamaroFred]

Originally Posted by San2cci

That's very interesting. I do have stock rims and TPMS sensors. Different tires but same size as stock. When I removed the stock throttle body I realized the plate was not fully closed. I have to push on it for it to fully close. I believe these should be in a fully closed state. When holding it up to the light I could see about 1/8" gap around throttle plate. Wondering if this could be causing my issue. Just not sure because this only occasionally occurs. I can go 50+ miles without it happening. I'll be replacing the new throttle body tomorrow so only time will tell!

The throttle body is never 100% closed. Even carburetors are never fully closed.

Pushing on it may have broken it.

[Zombie killer]

Hey OP. Did the throttle body fix your problem? I hope it fixes your issue as you have been plagued awhile with it. A bad TB was my first guess as to the problem. I have a PTB and had the same issue. Took off the TB and gave ita good cleaning as it was getting gunked up by the overflow from the catch can. No more problems since. I just remove and clean TB about once a year. But the TB internal electronics can go bad... but we cannot buy the part by itself. They stick us with buying a whole new TB. I guess they feel better this way and not have to worry about being sued.

[qkslvr]

I had a very similar problem years ago. Mine was a tuning issue do to the altitude, tuner at 7K+ and most of my driving is around the 2800-5000 area, as well as a very finicky NW 102 TB. eventually we got it sorted out.

[BJVCamaro]

Does oil in the intake manifold have anything to do with this problem? I cleaned the throttle body and worked fine for a while and then started the powering down thing again, I noticed that there is oil coming from intake manifold making the throttle body dirty again on the back side. Better question, what is causing the oil in the intake manifold?

[San2cci]

I dont drive my car very often but after installing the new throttle body and driving for a few months with no issue, it happened again yesterday. I contacted a different chevrolet dealer and made an appointment to have my car looked at. So for me the new throttle body and new accelerator pedal did not change anything. I will follow up after I get it into the other dealership. Hopefully they will have some ideas other than what I have already been told by the previous dealership. I'm still wondering if my tune could be causing this as it began happening after the tune was uploaded. I did flash back to stock and re upload the tune after the new throttle body install and it still eventually went to REM.

[christianchevell]

Sorry to hear your still having problems as Fred said long ago pushing the blade closed is not a good idea on the throttle body as it has plastic gears you can inspect when disassembling the TB...… In your place I would not be using the dealer but rather my electrical guru who is my tuner Tommy Wong as he has a couple electrical engineering degrees and he is who I use.

First though I would have done some things you have ; yet of course wondered and carefully inspected all pins inside any connections in the electrical harnesses reconnecting them........and if having any issue in appearance; mostly replaced connectors... as installing any new parts with misaligned pins can be shorting. You now state you flashed back to stock yet then you went back to uploading the tune again which to avoid a problem if it was with the tune you should not have done...……..

Just thought I would point this out, that and I think a auto electrical shop would more likely help you versus a dealership, and one that has installed aftermarket LS engine packages and with experience chasing gremlins...…. Good Luck. And of course making sure things are tight like the TB matters.

[Avenging Orange]

I'm curious why you never contacted Steve reference your tune....
He reached out to you twice. Seems you are throwing money at wild guesses.

[InFiD3ViL]

Originally Posted by Avenging Orange

I'm curious why you never contacted Steve reference your tune....
He reached out to you twice. Seems you are throwing money money at wild guesses.

Exactly.

I have contacted Steve privately a couple of times for things that we both knew could not have had to do with his tune, but because I was a customer, I figured it wouldn't hurt to ask. He could have told me to pound sand. Instead he gave me his opinion of the issue based on the symptoms and he was 100% correct.

Now, keep in mind there is only so much he can do or say if it is not related to the tune, as that opens liability issues, and he is also NOT our personal 'mechanic on call'. But he has never turned me away and has always at the very least been very courteous and interested in the issue.

This man has tuned 1000's of these cars in nearly every modification combination you can think of, so if there is an issue, he has probably seen it before.

[DJ_BigC]

Send me a PM if you want to me to give you all the diagnostics required to properly diagnose this.

If i had to take a swing at this. I’d tell you to replace your entire throttle body.. yes the entire ASSEMBLY and get an idle learn done. But that’s provided the dealer actually checked all the wiring and terminal tension for the related circuits. Replace it with an OEM part unless it’s discontinued. Your accelerator pedal has NOTHING to do with this DTC, the advice posted about the APP being the problem is wrong.

If people want a full non backyard bobs bait and camshafts type diagnostic breakdown, I can post one for everyone.

[frey.199]

Originally Posted by fz4k98

Try removing and cleaning the throttle body and mag sensor. It is a known problem on gm vehicles and I had success doing it. The carbon buildup is not much but messes with tps.

I keep getting this code every now and then but I have a stock brand new TB with a cold air intake. Where does the carbon build up come from? Could it be the exhaust? Clean my TB and fixed the problem until about 2-3 weeks later it happened again.