2003 Cobra - Idle slow to return to normal

[da28fan]

I have a 2003 Cobra with C&L inlet pipe/K&N/95 MAF, and Bassani cat-back and X-pipe (with cats). I installed the performance tune and use 91 octane premium. It runs fine but the idle is slow to return. It will eventually return to around 750, but it's slow to drop. First just over 1000 and then slowly down to 750. I checked the linkage on the throttle body and it snaps back ok when I release it. I heard something on the other end of the cable that follows once the linkage returns to idle position. Sorry I'm not an expert, but learning. Stock it idled at 600.

After I installed the exhaust, I occasionally get the P0153 O2 sensor message (O2 circuit slow, response - bank 2, sensor 1), but I've checked the O2 connectors and they are solid and the wires are not melted. Don't know if that has anything to do with the slow idle return or not, just an FYI.

Any suggestions? Thank you.

U7142
#144550
2003 Cobra
v.7r12d

[wayniac_00]

http://www.mach1registry.org/forums/sho ... hp?t=18330

[xjrguy]

Does the problem go away when the STOCK TUNE is restored to the ECU?

[mikel]

http://www.mach1registry.org/forums/sho ... hp?t=18330

Nice call....

[da28fan]

Just wanted to say thanks! I bought a plate off ebay and installed it in like 3 minutes and it did the trick. Simply amazing that such a minor, quick adjustment like an IAC restrictor plate did exactly what you said it would do. Again, thanks!

Oh, I've heard some people say that another similar change is to do the same with the EGR. Have you heard such? I've heard that putting hot exhaust back through the system isn't really a good thing, but it's done for emissions?? I'd be curious if anyone knows more about this. Not having any problems, just curious!

Again, thank you!

[Shaken]

Just wanted to say thanks! I bought a plate off ebay and installed it in like 3 minutes and it did the trick. Simply amazing that such a minor, quick adjustment like an IAC restrictor plate did exactly what you said it would do. Again, thanks!

Oh, I've heard some people say that another similar change is to do the same with the EGR. Have you heard such? I've heard that putting hot exhaust back through the system isn't really a good thing, but it's done for emissions?? I'd be curious if anyone knows more about this. Not having any problems, just curious!

Again, thank you!

Really the valve is very useful in prevention of detonation in part throttle acceleration. Part throttle acceleration uses mostly closed loop where the fuel management runs as close to stoichiometric 14.7:1 The EGR valve opens at part throttle to reduce the formation of nox gases and to help cool the leaner running engine so it doesn't detonate. In wide open throttle the valve is suppose to be close and you will be in open loop where the engine management runs on the tune so to speak which is a richer. http://fordfuelinjection.com/?p=64 this might be helpful.