1998 3000gt Base Model with SOHC starts then when warm runs rough and stalls


Asked by Aug 11, 2014 at 02:25 PM about the 1998 Mitsubishi 3000GT 2 Dr STD Hatchback

Question type: Maintenance & Repair

Thank you for your help. Car is a base model with 57k original miles. New tune up, o2 sensors and coil. Stock except for a K&N filter. The car starts runs well, then when warm runs rough and stalls. Dealer checked fuel system and electronics and could not find anything. Crazy! Any help or ideas would be greatly appreciated. Many thanks.

8 Answers


Try turning ac on when it's idling rough. Does it start idling ok or better now? If so might try cleaning your iac and throttle plate. Pay close attention to the throttle plate edges and the area of throttle body where it and the plate meet.

2 people found this helpful.

Thanks - a/c running/off made no difference. The iac looks clean and we cleaned the throttle plate and no change. Any other ideas?


Iac looks clean but does the plunger move in and out as it should?

1 people found this helpful.

Hello Thank you for responding. I played with the car again this evening. It is frustrating, the car will not kick out any codes, no check engine light. The light works and illuminates when starting the car. Ran great as normal for 30 minutes until warm, they ran rough and started to sputter. When I applied the gas it was like nothing was there gas pedal just went down without any engine response, then the car stalled. I was able a couple of times to apply the gas and rev the engine and then it appeared normal at higher RPMs and when I released the gas it came back to normal idle, then a few moments later the car again sputtered and stalled. Every time the car stalled it started again immediately and ran normal for a while before it repeated the above again. Again this only happens after being completely warmed up. It does seem like if I try hard enough I can prevent the car from stalling by revving the engine. Any thoughts would be super appreciated. Thank you.


Hi Dandyoun Iac looks clean but does the plunger move in and out as it should? Thanks for responding Can the IAC malfunction as your note above and not throw out a code? Thank you for your time. Regards,


B7p1 you cannot go by visual inspection on the IACV you need to put a voltmeter to it to check it,, and I agree with Dandyoun its most likely the IACV,,, could also be a bad water temp sensor but my moneys on the IACV,, here have a read on this link and do what it says and youll find out for sure http://www.stealth316.com/2-isc-iac.htm

2 people found this helpful.

Hi Daniel Thank you for your response. Can you please take a look at the attached file and let me know your thoughts. I had taken the car to the dealer and they said they tested everything including the IAC and found no issues, however who knows for sure. Wont kick out any codes. Thanks for your time

1 people found this helpful.

Yes one of these iac can malfunction without throwing any codes. Just a thought but have you cleaned and tightened you negative battery connections on the frame and motor? These cars do all kinds of weird things when this connection is not perfect. Could also be coil or throttle position sensor heating up and failing. Also check plug wires for areas of carbon tracking.

2 people found this helpful.

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