Mechanics

ROUGH IDLE IN GEAR THROTTLE POSITION SENSOR OR IDLE SPEED

1990 Mitsubishi Mirage • 100,000 miles

I have a rough idle only in gear and wandering / surging rpms. Ive replaced motor and trans mounts, idle speed control, spark plugs and ecm/ecu but no joy. Is it the throttle position sensor? Or transmission? I do experience some slip and odd shifts but only when all sensors are connected otherwise she shifts smoothly. I have no CEL.
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Mhooper87
April 16, 2012.




Check the valve clearances.

KHLow2008
Jul 21, 2012.
Had (supposedly) valves checked and adjusted. Could this be a gas cap problem? Mine is a little rusty with some crystallization but seems ok otherwise. It is the original cap.

When I give 15 seconds of ignition w no start then crank the ICS SEEMS to recalibrate meaning I get searching rpms again. Everytime it seems to search less and less. Should I just give it a week to try and sync? Someone also mentioned programming the (new ECU) any ideas around these two issues. Thanks again.

Tiny
Mhooper87
Jul 22, 2012.
The ISC is faulty causing the problem.

KHLow2008
Jul 22, 2012.
ISC is new from mitsubishi. Only a few months old. Wandering rpms are self resolving but I am getting a little random rpm surge when stopped in gear post MAF replacement. Vibration is still a problem still rough in gear at operating temp. Something is not telling the engine to lean out? Or increase rpms? While in gear at a stop. Its almost backwards meaning out of gear no ac rpms increase and idle is smooth in gear w or w/o ac rpms increase a little but not enough? And I get a steady shake through the steering wheel - shake stops as soon as i'm out of gear. Is throttle position sensor a possibility?

Tiny
Mhooper87
Aug 14, 2012.
Could use additional information on MAP location - but can not find it or any reference to it on 90 mitsu mirage.

Tiny
Mhooper87
Aug 14, 2012.
That means your vehicle is not equipped with MAP sensor.
How many mounts did you replace?
What are the idling speed under each conditions as described?

KHLow2008
Aug 14, 2012.
Mounts are maybe 3 months old. Reset idle again by ear. The car wants and does for a moment, run smooth in gear but then shaking starts and exacerbates I also hear some puffing like exhaust leak ( but had that checked )as idle lowers and shaking starts most noticeably when I first go in to gear.
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Tiny
Mhooper87
Aug 14, 2012.
Replaced all 3 motor mounts and 1 trans mount. 3 months ago

Tiny
Mhooper87
Aug 14, 2012.
Setting idle higher doesn't seem to help.

Tiny
Mhooper87
Aug 14, 2012.
I need to know the idling ccondition. Setting it higher would cause more problem as the computer would be compensating for too low rpm and decreasing when it gets too high.

By ear? OMG, so the idling surge is by ear too?

KHLow2008
Aug 14, 2012.

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