04 cobra idling issue

[piss&vinegar]

Just started noticing a small idling issue this weekend. When I am sitting at a light the car will idle down to ~500 rpms then back up ~750 rpms. I checked all connections under the hood and there was a couple of loose connection on the intake after the MAF so I tightened them and took it out for a spin. When I got to a stop light it still continues to happen. I then cleaned the K&N filter and re-oiled it but the problem is still happening. I did have one head replaced because the #7&#8 valves were burned but that was about 1500 miles ago. I did a search and the only thing I can do is to clean the MAF but is there anything else I can do? I have a K&N FIPK, MRT catted H pipe and Flowmaster exhaust and everything else is stock. The vehicle has ~37,000 miles. Thanks for any help!!
:shrug:

 

[Sonic605hp]

Reflash will cure it (had it with Redfire)....either go to Ford or have your tuner do it.

 

[Juruense]

Does it only do this when the climate controls are set to a position that runs the compressor? The compressor runs in all positions except the ones immediately to the left and right of straight up (off).

If you car is low on freon the a/c compressor will cycle on and off causing this behavior.

Another thing you could try is resetting the PCM and allowing the car to re-learn its fuel trims per the procedure outlined in your user's manual.

 

[piss&vinegar]

Thanks I will try those suggestions. It is weird because it happens sometimes and not all the time. Based upon some other things I tried out I thought it could be the alternator but according to my a voltmeter I have in the car the voltage stayed at 14.2 and when I turned on the radio it went ot 13.8 - 13.9 V so I don't think it is my alternator. Anyway, keep the suggestions coming!! It just seems like the engine is loaded down and then it is not and idles normally.

 

[piss&vinegar]

bump

 

[piss&vinegar]

Just an update to this. I have been doing some research into this and discovered there are 2 sensors that control idle. IAC(Idle Air Control) and Oxygen sensors. I cleaned the Idle Air Control and that help a little but still did not cure it. Well, the other day I went to a muffler shop because my exhaust sounded weird. Well, the balance part of my H-pipe had come loose. They welded it since it was held with clamps. I have noticed that ever since that was done the idling problem is gone. I think outside air was getting into the exhaust that was not going through the intake and causing the oxygen sensors to report back incorrect values so the car would never idle smooth. Anyway, check you exhaust if you are having this problem and if you can get it welded and see if it helps. It did in my case!

 

[04CobraMatt]

Just an update to this. I have been doing some research into this and discovered there are 2 sensors that control idle. IAC(Idle Air Control) and Oxygen sensors. I cleaned the Idle Air Control and that help a little but still did not cure it. Well, the other day I went to a muffler shop because my exhaust sounded weird. Well, the balance part of my H-pipe had come loose. They welded it since it was held with clamps. I have noticed that ever since that was done the idling problem is gone. I think outside air was getting into the exhaust that was not going through the intake and causing the oxygen sensors to report back incorrect values so the car would never idle smooth. Anyway, check you exhaust if you are having this problem and if you can get it welded and see if it helps. It did in my case!

Glad you fixed it, I would unplug your battery one night to reset the long fuel trims since its been building an average on bad readings for the past little while.

 

[sho95]

Mine has been doing this exact same thing since stock.
I have been through a couple of tuners and still have the problem.
I am on a VT block and both new heads and still have the problem.
I have a complete exhaust KOOKs headers (welded)xpipe and borla stinger
replaced the IAC
cleaned the maf
replaced the frps
took out the pprv
GT pumps modified FPDM
I hope you have better luck than me.
Mine even goes so far as to stall after it bounces from 500 to 750 three times if i dont kick the throttle.