Hi, have a 98 Sebring conv. with a Mits 2.5L V6. Decided to treat it to a tune up after 158,000 miles.  Also cleaned out injectors throttle body, etc.  Now while sitting at idle in gear, engine stutters real bad.  Can provide temprary relief by using Castle Products fuel injector cleaner (only one that works).  We dropped the tank, no forieign matter, we checked the EGR and IAC, seemed to be working.  When car is cold and computer is comtrolling the fuel flow it is OK, after warming up is when the stuttering starts (worse with AC on).  Went ahead and replaced all injectors (expensive), figured only thing left. Still only relief is to pour a can of expensive fuel injector cleaner in the tank, good for 1/2 a tank.  Should I maybe go back and replace the IAC assuming it is a flow control problem?  Prior to all this, the car ran great with no problems.

Thanks in advance.

Also welcome to the site, and TSX knows the sixes pretty well, even if he turned his back on these lovely cars.

From the Haynes Repair Manual:

The TPS is located on the end of the throttle shaft on the throttle body. By monitoring the output voltage from the TPS, the PCM can determine fuel delivery based on throttle valve angle (driver demand). A broken or loose TPS can cause intermittent bursts of fuel from the injectors and an unstable idle because the PCM thinks the throttle is moving.

Yep, its controlled by the computer  . My car did the same thing initially, where it ran fine when cold, but went into "crappy idle mode" after warming up.

Using a fuel addative won't help....I tried it personally. Replacing the sensor is the solution, if that is the problem. Just pop the hood with the car running and wiggle the sensor. It will idle rough if the sensor is faulty (at least it should!).


Yeah, but the car turned on me first!!! 

The TPS could make it idle high, but it could also cause the trottle body to close, causing low idle too.


If it looks clean, it should be ok. But, if someone attempted to clean the throttle body using TB cleaner, they might have hosed down the IAC causing it to look clean, but malfunction.


i think that injector cleaner is only a temporary solution in most cases. The stuff is just too diluted to be effective in the fuel tank IMO.

I hope this helps!