My daughter has a 98 sebring convert. jxi 2.5 engine.I have been working on it for over 3 months trying to find what is causing it to run bad. here is the problem when u crank it cold it runs rought and will not gain any rpm. it runs like this until the engine reaches normal temp according to gauge then if you rev the engine till it clears out and stops misfiring it will run smooth and you can drive any where you can cut it off and come back in 30 min or some crank it and go with no problem but if you let it cool done it back to the way it was. It set no codes other than p0300 which is multiple misfires no special cylinders i have scanedit multiple time with no new codes. It has been to dealership and they scanned it reprogramed the pcm no help
here is a list of parts suggested by other machanics i know to try and i have tried them

fuel pump and filter
clean injectors
IAT sensor
MAP sensor
Crank position sensor
Cam position sensor
Throttle Position sensor
Idle Air control unit
Distrubitor
dist Cap/Plugs and Wires
Coolant temp sensor
have grounded the fuel pump at the rear of car
asd relay
fuel pump relay
PCM
after all these parts it still runs the same
fyi we have found out that what it seems like is causeing it to run bad is that the idle ctrl unit is being pulled wide open and when the engime clear up and stops misfiring it is closed if i put my finger over the hole it runs better when it is cold but not a 100% right. I am at my wits end with this about ready to power a gallon gas on it and kight a match just to get rid of it but my daughter can't afford anything else right now and i am strpped paying for college for 2 Please help.

 

Just guessing here, but one of the inputs to the computer that controls the idle air control motor is the ambient/battery temperature sensor. That's different from the intake air sensor. Not sure where it's located on your car, but probably somewhere near the battery.

Like I say, it's just a guess.

 

well first thing i would do is to check for codes.

 

Dodgetech1 asI stated in my post the only codes being giving is multiple misfires P0300 other codes set whenI disconnect a sensor but that is expected it is during normal opertion that the only codes are P0300

 

I didn't see the EGR on your list, or the PCV system (valve and hoses). You could check those out. Also, the fact that it runs better with the IAC covered makes me wonder if that is sticking or if there is a vacuum/intake gasket leak somewhere I think that would result in a high idle though, since the computer would simply adjust fuel for the increased air.

 

I blocked off the egr valve tube at intake and yes the pcv valvlle has been changed and the hose was checked to make sure no crack and it was not clogged. I have changed so much on this thing i can't rember everything that has been tried I think at this point the only sensors not changed are the o2 sensors. and from what i have been told the o2 sensors are not used till engine reaches normal operating temp which when that happpens and you clear the engine it runs fine.

 

Have you checked the vacuum system for leaks? The power brake booster and cruise control operate off engine vacuum. There's a check valve on the booster that maintains vacuum for everything. There's a vacuum reservoir in front of the battery location under the left headlight.
You should be able to check the whole system by unplugging it at the booster and blocking it there. If the idle improves, then the problem is somewhere beyond where you plugged it.

 

I have had avacum guage on it and it hold steady when engine is running right and since engine will run good after it warms up and you clear it out at high rpm that basicly tell s me that it's not a leak in anythin that 's not controled by the pcm or some sensor. if it was a bad chec kvalve or hose it would be bad all the time..

 

Your problem sounds like EGR even though you blocked it.

 

When you shut the engine off is the a "sucking" sound just for a second or two??

Mike