Recently I replaced the ac compressor on my 05 vette. While doing so I installed a 160 degree thermostat and cleaned my throttle body. When I started the car it idled like it normally did during a cold start around 1000-1100rpm but as it warmed up the idle increased to over 1100-1200rpm. The car had a cam installed 3 years back and tuned by a reputable tuner with no issues and over 20k miles, so I know it has nothing to do with the tune. The idle is normally supposed to sit at around 850-950. I assumed it was the colder thermostat as many have had issues with them so I installed a new ac delco 187 degree in it. There was no change. During this time the car threw a P0507. I changed the throttle body as I read many have had issues with them being ruined after cleaning and did a relearn through hptuners but that also did not fix the problem. I have used a smoke machine and checked for vacuum leaks and found nothing. Short and Long term fuel trims look normal during idle and driving. The headers will also become glowing red during idle. The car will also occasionally give the Check Coolant Level Message. I have no idea what to do next. My MAP reads 60kpa at idle which should be normal for a cam. The MAF reads 4,058hz 2.43(lb/min) at idle. What should I check next as I am completely stumped. Only thing I can think of at this point is the ECT sensor being bad. Any help would be appreciated.

 

What are your Long and Short term fuel trims at idle ??...your PCV valve is a “controlled” vacuum leak..check for it being stuck open...I would also clamp off your brake booster hose as it may have an internal leak which may be hard to see with a smoke machine...and remember if you have a vacuum leak your fuel trims will decrease with an increase in RPM.

 

STFT B1 AND B2 AT idle remain between 0-5% and my LTFT for both banks remain between 0-0.8%. Theres no PCV on the LS2 so that can't be an issue. Ive tried capping off the evap system and brake booster as well while doing the smoke test but had no leaks.

 

Even though you tried an idle relearn you can try disconnecting the battery for 5 minutes and them touch both battery terminals together for a few minutes...what makes you think it’s the ECT sensor ??

 

I tried the battery disconnect with no improvement. Also replaced ECT sensor assuming maybe the car was getting a false reading causing my check coolant level message but it didn't fix the issue either. At this point I've tried practically everything.

 

Even though a new TB did not fix your issue was an OEM TB used ??...how did you clean the TB ??...I just open the TB with my scan tool and use cleaner and an old toothbrush...no need to remove it to clean if that's what you did. Does your HP Tuner show a TP Desired and TP Actual Data Pid ??..is the PCM in "Closed Loop"...wondering how your glowing headers fit into all this...all these MAP and MAF numbers you quoting are at 1100-1200 RPM ??...my spark advance is about 35 degrees at 1100-1200 RPM...to bad I'm not still living in Central NJ I was only 25 minutes or so from Staten Island so I could have hooked up all the "heavy equipment" to the car...LOL !!!

 

Yes I purchased a used oem throttle body as they are discontinued and I didn't want to go aftermarket. I had the throttle body off when I was doing the ac compressor so i wiped it clean with TB cleaner before I installed it. I attached my logs of idle and driving if you want to take a look lol. Thanks

 

Sorry but I can't view these files !!!

 

The hot exhaust is a sign of a very lean condition, a vacuum leak.

 

After looking at some more logs I found an issue. The car is commanding the throttle position to be 14.5% but the actual position of the Throttle body is 23.5%. What would cause a throttle body to open more than it should.

 

Usually it’s a dirty throttle body but since you changed it I would see if the TB opens and closes...with key off check it...this is my TB numbers from my scan tool.

 

Maybe check TAC & it's circuit?

 

I hope this helps someone in the future experiencing similar problems.The problem ended up being the tune. Although the car ran perfect for 3 years with the previous tune, the min aiflow was set with that dirty throttle body. So after adjusting the airflow in the tune, the car now runs perfect. After talking to a friend with a built zl1, turns out he experienced a high idle after cleaning his throttle body as well and needed his tune adjusted. Although your car may run great with a tune you have had for years, these throttle bodies seem to need the tune adjusted after cleanings or replacements. I have been chasing this problem for months and I hope it saves someone the time and headache. I appreciate the help from anyone who contributed to the thread.