Drolly

Sorry in advance for the lengthy post but I think some background information is important. I am a professional heavy equipment mechanic. Diesel guy more than a gas guy these days and haven't spent much time playing with an LS1. My father in laws car is a 2002 Trans Am WS6. I just resealed the valve covers, resealed the pan under the intake that houses the knock sensors, replaced both knock sensors and harness while in there, replaced all intake manifold seals and replaced the throttle body seal. When I started the repair I found the PCV line that runs from the rear side of the left valve cover across to the right side valve cover and up to the throttle body was bad. I told him we would need to replace it. He actually had the part and I found a date on it from 2008! He's been driving the car with that PCV line bad since then. The line was completely rotten at all the rubber joints and has been doing nothing. I have put the car back together using all new seals everywhere like I mentioned but am having throttle issues now. The startup idle is very erratic. Surges from 300-1400 RPMs. Once warm it get better and idles stays around 900. If you open the throttle slightly there is a very bad dead spot. When you let off the throttle the idle bounces erratically again. Three times now the idle has jumped up to 2400-3000 and it stays there. The car is throwing codes. If you clear them the first one to come back is MAF circuit. P0101. Then after a few minutes it throws a P0106 code. After warm the P0101 code take quite a while to come back and the P0106 will not go active if the P0101 is not active. I checked the MAF via Fluke multimeter. It has a good 12 volts and 83.1 ohms ground which seems acceptable for a PCM ground circuit. The Hz reading is not stable but not what I would call erratic either and it does fluctuate exactly as the idle does. Hz goes low when the idle is low, goes high when idle is high, very steady reading when idle is smooth. I pulled the IAC valve to check it. Pressed the plunger in and installed the IAC valve back in the TB. When I start the car now the throttle "gets stuck" every time you hit the throttle. Stays around 2200 RPM. I pulled the IAC valve back out and the plunger did move and does seem to have touched the seat but now the idle acts that way all the time. That seems to be the problem but y'all here on this forum play with these engines much more than I do. Any help is appreciated and again, sorry for the long write up. Just wanted to cover all bases.

SouthernRex

Have you tried cleaning the MAF? A dirty MAF will wreck havoc on engine performance.

1 FMF

iTrader: (1)

Are you the original owner(s) ?
Has the car had any modifications, either that you know of or that you can tell?
First thing that comes to mind is someone could have reprogrammed the engine computer so that might be working against you.

Thing with maf and pcv is, as the intake manifold sucks air out of the crankcase via pcv valve, air that has to enter back into the crankcase. For how that happens does that makeup air pass through the maf sensor ? I don't remember on the ls1 if that's the case, if it is then that means a leak anywhere on the engine that let's air in will be unmetered air by the maf and be a vacuum leak and cause high and erratic idle. Something as simple as oil dipstick o ring, the dipstick not being pushed all the way down, and oil fill cap can cause it.

Also check the throttle body blade and see if someone drilled holes in it, if the car had a previous owner and might have been modded such as a different cam. But assuming car is stock unmodified, make sure throttle body isn't all carboned up and that the blade isnt sticking partially open on you.