ROUGH IDLE IN GEAR 1990 MIRAGE THROTTLE POSITION SENSOR OR IDLE SPEED

  • Tiny
  • mhooper87
  • 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.

Do you
have the same problem?
Yes
No
Monday, April 16th, 2012 AT 2:47 AM

48 Replies

  • Tiny
  • ASEMaster6371
  • Expert
  • 25,556 posts

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

Roy

Was this
answer
helpful?
Yes
No
Monday, April 16th, 2012 AT 2:49 AM
  • Tiny
  • KHLow2008
  • Expert
  • 41,997 posts

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.

Was this
answer
helpful?
Yes
No
Monday, April 16th, 2012 AT 11:50 AM
  • Tiny
  • mhooper87
  • Member

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.

Was this
answer
helpful?
Yes
No
Monday, April 16th, 2012 AT 1:54 PM
  • Tiny
  • mhooper87
  • Member

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.

Was this
answer
helpful?
Yes
No
Monday, April 16th, 2012 AT 1:57 PM
  • Tiny
  • KHLow2008
  • Expert
  • 41,997 posts

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.

Was this
answer
helpful?
Yes
No
Tuesday, April 17th, 2012 AT 1:40 PM
  • Tiny
  • mhooper87
  • Member

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

Was this
answer
helpful?
Yes
No
Tuesday, April 17th, 2012 AT 5:54 PM
  • Tiny
  • KHLow2008
  • Expert
  • 41,997 posts

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.

Was this
answer
helpful?
Yes
No
Wednesday, April 18th, 2012 AT 1:53 PM
  • Tiny
  • mhooper87
  • Member

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.

Was this
answer
helpful?
Yes
No
Thursday, April 19th, 2012 AT 12:22 AM
  • Tiny
  • KHLow2008
  • Expert
  • 41,997 posts

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.

Was this
answer
helpful?
Yes
No
Thursday, April 19th, 2012 AT 1:14 PM
  • Tiny
  • mhooper87
  • Member

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.

Was this
answer
helpful?
Yes
No
Sunday, April 22nd, 2012 AT 8:04 PM

Please login or register to post a reply.

Similar Questions