I've been having this stumble problem for quite some time now, I've been trouble shooting the exhaust O2s for a while and ruled them out as the cause. Anyway, what happens is the engine idles really funny while the car is moving. Say I'm going 50 km/h and take it out of gear it'll sit at 1500. Then every couple of seconds it will shudder, drop about 500 rpms and then go back up to 1500. It first started happening after I installed my headers.

Most of the time the car idles normally at 800, it's just on occasion that it'll do this. Any idea what's causing this?

At the time of the install I also installed Taylor OTVC wires and a MSD ignition coil. I have pressure tested the engine, as well as tested the fuel pressure. No problems there. I plan on replacing both the wires and the coil again, to rule them out as a cause.

 

Wow, bumped to page 2 already. Pretty active right now, nobody knows what's going on or has any ideas?

 

Someone's gotta have some advice.

 

ttt

 

Sounds like your IAC. Could be caked with carbon. Won't idle right that way. Buy a new one or you can try to clean the old one.