running rough on warm up

[Mustangous]

I am having rough idle issues mainly only at take off after car is warm. I got a P0304 code, which is cylinder 4 misfire. I switched the coil packs, plug wires and plugs and still same code. I think something is giving me that false code.

The syptoms is after warmed up and when i go to give it gas or take off it runs rough. It also seems like when idling, it is slightly surging, but very little.

I checked for vacuum leaks by spraying starting fluid over all the vac lines, but no increase in idle. So seems good.

I was thinking maybe it could be the iac or tps. I was gonna ohm the iat sensor today see how that reacts. Any ideas, help, or how to troubleshoot each.
Thanks
Troy

[dorman68]

I would try swapping fuel injectors and see what happens. If you still get no changes in cylinder misfire codes I would then do a compression test.

[Mustangous]

After googling the symptoms of each sensor i think it may be the tps sensor. It sound like the exact thing.

They put the issue in better words then me...

A car that seems to hesitate or stumble during acceleration may have a faulty throttle position sensor. AA1Car.com explains if the sensor sends the wrong throttle position message to the engine, the engine will not add extra fuel to the mixture until the oxygen sensor feedback circuit steps in to correct the imbalance. This momentary miscommunication will cause the car to hesitate. Sometimes a sensor may develop one or more dead spots in its response, so as the potentiometer passes those spots, the car hesitates. Sensor wear often causes a dead spot just above its normal "idling" position.

Read more: Symptoms of a Bad Throttle Position Sensor | eHow.com http://www.ehow.com/about_5890709_sy...#ixzz1BIga8Dcq

Wouldnt i get an engine code if it wasnt working properly? I will put a volt meter on it today and see what i get, but not sure if i will be able to tell if the computer isnt telling me.

[Mustangous]

Originally Posted by dorman68

I would try swapping fuel injectors and see what happens. If you still get no changes in cylinder misfire codes I would then do a compression test.

I am not getting a rough idle all the time only on acceleration, but will try.

Thanks!

[dorman68]

Originally Posted by Mustangous

I am not getting a rough idle all the time only on acceleration, but will try.

Thanks!

Perhaps checking the fuel pressure during driving might point you in the right direction.

[Milky]

i would pull the plug and check it. i almost want to say its fouled out.