Car runs fine, rough idle, WTF?
 

Like the title says, I have a rough idle (started happening after a few pulls) but the car runs fine. I checked:

- The MAP sensor
- The compression (with a piston engine one for now)
- Plugs and wires are fine
-Listened to the engine with one Trailing plug out on each side (sounded uniform to all three sides.
- I have 15-18 Hg of Vac at 850 rpm idle
- there is absolutely no power loss (didn't check in boost, because I'm worried I'll break something)
- I have a Power FC and no Airpump, Accelerated Warmup, and secondary air injection

The only other thing I notice is that the exhaust seems to be leaking somewhere under the car. Could it just be a Cat that finally gave up. I know that without the airpump it has a shorter life, but it doesn't stink like sulfur, and I only took the Airpump off 500 miles ago. It does have 120K on it though.

Could the cat cause that problem? or did I blow a corner off a seal or something little inside the engine?

X...

It's probably super rich because you don't have an airpump. My car with stock ECU and no airpump has about a 10:1 AFR at idle via wideband. :(

tps

that cat will get clogged up soon. you can try to adjust the fuel at idle to see if it smooths out. also mine was rough. it turned out the egr was stuck open a bit. a block off plate later and np

Thanks for the responces so far, now at least I have a few other things to look into.

X...

I have the same damn problem with my car as well..... the motor is street or race ported and the ideling really sounds like crap. The idle hunts baddly as well.....
But!!~~ just like you said... the car runs like a champ!!!~~
Its just the idle that is the problem.. I have a PFC as well. What is the biggest problem
with idleing problems guys??? IS it the TPS sensor??? the funny thing is that when I take the electrical harness out for the TPS it really doesn't change idle that much.... I can still run the car...... hmmmmmmm
anyways... help us out guys~~
Thanks

This is with my car it ran fine for 500 miles. I noticed today that there is a lot of oil in the throttle body for having cleaned it a 50 miles ago. I need to check that still. If that doesn't work I'll need to see if I can take it to the dealer, but my dealer wouldn't know an FD if he got hit by it.

X...

Try adjusting the screw below the TPS sensor. My idle used to bounce between 1k and 1.5k. I adjusted that screw so it was almost all the way in and all of a sudden my idle dropped to 900rpms.