The Top DSM Community on the Web

For 1990-1999 Mitsubishi Eclipse, Eagle Talon, Plymouth Laser, and Galant VR-4 Owners. Log in to remove most ads.

  • Update Your Password Today!

    We have implemented tools to identify member accounts using insecure passwords and will be locking those accounts until their passwords are updated. Don't get locked out of your account - update your password today, and ensure your account has a valid email address on file. Read more here...
Please Support Morrison Fabrications
Please Support STM Tuned

1G Erratic idle and bad acceleration


Probationary Member
Aug 22, 2022
Penticton, BC_Canada
My 91 laser rst started to idle erratically when cold ( 1500-2300 rpm) and since it started doing that the car also accelerates fine to about 3500 rpm and then then the car gets very sluggish and feels like it’s holding back, it usually flies at 3500 rpm. I’m still building boost and my a/f ratio is normal. I do have a CEL for a knock sensor and O2 sensor. Could this be the cause of my problems?


DSM Wiseman
Nov 19, 2011
oklahoma city, Oklahoma
Please submit a profile for the car. Tell us what you have checked if anything. Yes the CELS are a problem. O2 not so much at WOT. Perform a boost leak check.


5+ Year Contributor
Dec 26, 2017
Elyria, Ohio
The knock sensor and o2 sensor are definitely issues that need to be addressed. I can say I once had an ecu with a bad knock board, triggered the CEL for the knock sensor and caused it to fall on its face just as you described.

A bad o2 sensor or the sensor not getting the signal to the ecu will cause all kinds of issues due to the fuel trims being all out of whack. Depending on what the ecu thinks it’s seeing from the o2 sensor could make it do things like idle weird or start stumbling at 3500rpm.

The CEL is coming on, it’s telling you that there’s most definitely a problem with those parts or associated circuitry, that’s always an issue. Don’t go driving around trying to get into boost when it’s telling you there’s obvious issues.
Support Vendors who Support the DSM Community
Boosted Fabrication ECM Tuning ExtremePSI Fuel Injector Clinic Jacks Transmissions JNZ Tuning Kiggly Racing Morrison Fabrications RixRacing RockAuto RTM Racing STM Tuned

Latest posts

Build Thread Updates

Vendor Updates

Latest Classifieds