Newbie here. I am trying to nail down the exact solution to my problem. I have seen a number of similar threads on this issue, but the more I read the more solutions (and parts to clean or replace) there seemed to be.

The Problem: On engine start, RPM surges between 1000 and 2000 RPM every second or so while car is in park. Once in drive surge appears to go away. CEL is on and steady. After a few miles of driving TCS comes on and when I lift off gas the car shudders. I put the car in neutral and noticed there is still a small surge in rpm of maybe 50-100 rpm every second. Autozone pulled the code as a P1129.

I appreciate your advice

 

P1129 = MAP Higher Than Expected

Dont know why its showing that. Maybe because of the IAC. With RPM fluctuations like that its the IAC. it either needs to be cleaned or replaced. The TCS light on means nothing. Its programmed to come on with the CEL.

 

Is it possible that a bad ICV is somehow triggeirng the TCS? It seems like once the TCS comes on I get a noticble jerk on throttle lift.

 

The light has nothing to do with it. Its programed to come on with the CEL for most things. Forget that light is even on. Its most likely caused by the IAC. Take it off and clean it out. Sprat just a dab of WD40 in it and reinstall it. Pull your clock back up fuse for 10 min and then put it back in. That will reset any CEL light. See if that takes care of the problem

 

Just an update. I got the IAC pulled turns out the entire interior was covered with a layer of oily dust including the spring loaded gate that controls air flow. I cleaned the works with carb cleaner. I also cleaned the throttle body and chambers the lead from it into the IAC. Little WD40 on the parts and got it back together. Took an hour and a half to disassemble and about 30 minutes to clean and put back together. Car started right up and idled smoothly. Test drive revealed no problems and TCS did not come on.

Thanks so much for the help and info.