ROUGH IDLE IN GEAR THROTTLE POSITION SENSOR OR IDLE SPEED

1990 Mitsubishi Mirage

Tiny

mhooper87

April, 16, 2012 AT 2:47 AM

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.

FOUND 1053 RELATED QUESTIONS

48 Answers

Tiny

ASEMaster6371

April, 16, 2012 AT 2:49 AM

I would look for a vacuum leak. Have the intake system smoke tested to find it. Intake gaskets are common.

Roy

Tiny

KHLow2008

April, 16, 2012 AT 11:50 AM

Some trouble codes do not trigger the CEL for older models so it is good to check for trouble codes.

http://www.2carpros.com/articles/mitsubishi-trouble-code-definitions-and-retrieval-procedure-for-odb1-system

Try above link if you want to check for trouble codes.

Tiny

mhooper87

April, 16, 2012 AT 1:54 PM

If I have no CEL do I have codes?
Do notice what sounds like an exhaust leak that I only hear in gear stopped at traffic and after isc lowers rpms revs back up then drops to rough idle.

Thanks this is driving me nuts. 1 month and no one has a solution. Will get smoked and advise.

Tiny

mhooper87

April, 16, 2012 AT 1:57 PM

I am correcting original post. Transmission jumps in / out of gear most notably when I'm off the gas. Also seems to shift prematurely. Thanks again.

Tiny

KHLow2008

April, 17, 2012 AT 1:40 PM

Not all codes trigger the CEL and for transmission, most codes do not show unless you use the diagnostic method to check.

If you are not going to follow advise, I will stop here.

Have a nice day.

Tiny

mhooper87

April, 17, 2012 AT 5:54 PM

Smoke test was negative. Maybe I led on to know more than I do. How do I perform code check via diagnostic method? Thanks!

Tiny

KHLow2008

April, 18, 2012 AT 1:53 PM

For engine trouble code, click the link provided in previous post.

Transmission Self-Diagnostic Test Procedure

Connect analog voltmeter or LED lamp to diagnostic connector terminal No. 10. And ground. See Fig. 7. Turn the ignition switch to the ON position, and TCU memory contents will start immediately.

The sweeping needle of the analog voltmeter or the blinking LED lamp would indicate the fault code.

Tiny

mhooper87

April, 19, 2012 AT 12:22 AM

Mechanic says he doesn't have software to run an engine diagnostic code check? Is there special software required? He did find fixed idle and set idle screws "way out of specs". No more revving / wandering RPMs but still rough idle in gear at full stop. I hear a slight exhaust (?) Leak only when: lights on, turn steering wheel, press brake pedal when in gear does seem to coincide with rougher idle. Mechanic says its negligible and thinks its as good as its gonna get. I can't believe it. He says 10 cycles of 35 mph to 55 mph required to recalibrate ECU/ECM. And to run a tank of Hi Octane to smooth it out.

The car wants to run smooth in gear and does momentarily on slowing down but once at a full stop starts running rough & shaking. It smooths out as soon as I let off brake and start to roll just a little. Will try a trans specialist (AAMCO?) For Trans codes. Thanks again.

Tiny

KHLow2008

April, 19, 2012 AT 1:14 PM

Did you read my replies? I outlined the procedures for retrieving both engine and transmission trouble codes.

Your idling speed is too low and not stable. If you did not clean the throttle body, do so. Have the valve clearances checked as well.

Tiny

mhooper87

April, 22, 2012 AT 8:04 PM

No codes on engine or trans. Cleaned throttle body no difference. Latest mechanic says torque converter is bad. Going for rebuilt trans - any suggestions or good prices - or places to steer clear of? I see rebuilds for $500 sound about right to you? Thanks again.

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