Rough idle when hot

[Walwal44]

I have a 1995 eagle talon tsi awd and when its started cold the engine idles perfectly fine but once its up to operating temp and i go to start it, it idles very rough bouncing between 500-800rpm. I cannot figure it out.

 

[miliman13]

Sounds like your hearing the difference between open and closed loop.

See the hyperlink:
https://www.ecmtuning.com/wiki/fueltrimupdatepoints

FYI... we can't help you unless you do more work and narrow down your probabilities.

 

[Walwal44]

Sounds like your hearing the difference between open and closed loop.

See the hyperlink:
https://www.ecmtuning.com/wiki/fueltrimupdatepoints

FYI... we can't help you unless you do more work and narrow down your probabilities.

Its in closed loop. I have gone over the ignition system and that all came back good. It is in timing. The fuel filter is original but i cannot get the banjo bolt out. There are no vacuum leaks. And the pcv is new. Oil pressure is okay. It has unknown miles on the engine because it was replaced.

 

[Walwal44]

Its in closed loop. I have gone over the ignition system and that all came back good. It is in timing. The fuel filter is original but i cannot get the banjo bolt out. There are no vacuum leaks. And the pcv is new. Oil pressure is okay. It has unknown miles on the engine because it was replaced.

When you start the vehicle it stumbles and struggles to run for about 5 secs and then it flattens out and ildes perfect. It only happens when the vehicle is started at operating temp. It does not make any bottom end noises but it feels like it is missing. It has good compression (cant remember it off the top if my head but was in spec)

 

[Detail]

I'm guessing that you do not have the stock fuel pressure regulator installed and perhaps the two vac lines from the sensor on the firewall near the brake master cylinder are not connected.

 

[Walwal44]

I'm guessing that you do not have the stock fuel pressure regulator installed and perhaps the two vac lines from the sensor on the firewall near the brake master cylinder are not connected.

They are connected and yes it is original

 

[jman1699]

Closed loop should run smoother because computer is calculating fuel trim unless you have mods and not in parameters of original tune. I agree with detail probably a fuel problem, id smack a fuel pressure test and check go from there

Also any smoke on start up

 

[Detail]

Do a search on "vapor lock". That should point you in the right direction. There are quite a few things it could actually be.

 

[Walwal44]

Closed loop should run smoother because computer is calculating fuel trim unless you have mods and not in parameters of original tune. I agree with detail probably a fuel problem, id smack a fuel pressure test and check go from there

Also any smoke on start up

No smoke on start up

 

[PlanZero]

Does the idle even out after 30 seconds or so? Apparently this is a common problem; both of mine do it on hot starts, on hot days especially. I used to care, then after chasing the problem with no luck I just gave up.

 

[Walwal44]

I figured it out. I noticed that my check engine light wasnt coming on when i turned the car on. Pulled the cluster and the PO pulled the buld. Hooked up a modis and it i had a code for first O2. Replaced it and havent had a problem since. Sorry for the time jt took to relpy