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1G Bad idle when it warms up

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Moovingon1GEclipse

Probationary Member
19
3
Jan 28, 2022
Beja, Europe
So either i didn't look hard enough or i just didn't find any information on this...

I deleted my AC (removed the belt + the support pulley and nothing else) and now the car has good idle when cold but when it warms up the idle is sometimes good, sometimes a bit jerky. When it gets jerky the most is when the fan for the engine turns on.

Something else I need turn off from the AC that maybe pulling power causing this? Because the AC fan before the cooling fan turns off it also turns on for like a split second (but always did that)

I'm going to clean the MAF sensor, throttle body and FIAV because it might just be some deposits that stacked up. But wanted to ask first in case someone has any ideas/suggestions.

Thank you in advance

Stock NA 1g d22a Eclipse 93
 
Last edited by a moderator:
What RPM does you engine idle at once it warms up?

Have you checked to make sure that your Idle Position Switch (IPS) is working?

Verified the base ignition timing with a light while grounding the timing check connector?

Checked for vacuum leaks?

When things are working correctly the IPS tells the ECU when it should control the idle speed. The ECU will step the Idle Speed Control (ISC) Stepper motor in and out to adjust the amount of bypass air going around the throttle butterfly. The Basic Idle Speed Screw (BISS) controls the default air bypass for idling and the ISC adjusts it.

During warm up the Fast Idle Air Valve (FIAV) under the throttle body provides additional bypass air to raise the idle speed and assist in warming the engine up. As the coolant temp increases the FIAV closes and the idle speed is controlled by the BISS and ISC.

Any air leaks abound the throttle body, vacuum leaks, overly tight throttle cables, defective PCV valves, etc will cause idle issues. The most common is the surging up and down between 800 and 1500 RPM.
 
What RPM does you engine idle at once it warms up?

Have you checked to make sure that your Idle Position Switch (IPS) is working?

Verified the base ignition timing with a light while grounding the timing check connector?

Checked for vacuum leaks?

When things are working correctly the IPS tells the ECU when it should control the idle speed. The ECU will step the Idle Speed Control (ISC) Stepper motor in and out to adjust the amount of bypass air going around the throttle butterfly. The Basic Idle Speed Screw (BISS) controls the default air bypass for idling and the ISC adjusts it.

During warm up the Fast Idle Air Valve (FIAV) under the throttle body provides additional bypass air to raise the idle speed and assist in warming the engine up. As the coolant temp increases the FIAV closes and the idle speed is controlled by the BISS and ISC.

Any air leaks abound the throttle body, vacuum leaks, overly tight throttle cables, defective PCV valves, etc will cause idle issues. The most common is the surging up and down between 800 and 1500 RPM.
I followed the VAQ about fixing idle with the BISS by grounding the ISC and turned the BISS to good idle, now when fully warm it idles around 800ish but it can jump from 850 to 500ish and go to 1.2kish and fall down to 800.
Full cold start idles around 1.5k and starts to lower all the way to around 850 but when it's fully warm the rough idle starts ... i just actually experienced after posting this and driving it. I do believe it to be something electric related, because there's a sound if I listen quietly and closely it sounds like loosen sparks ... but I did refit the sparkplug cables and everything else I touched (wich wasn't much actually).

My headers are cracked and so I have a leak there and I'm waiting on the new ones to arrive ... but I don't believe it's that because it was running good with the leak before ... so I don't think that's the reason for it. And the car kinda lounges back and forward around 2k rpm ... this should happen when the car is about to stall ... it's not really noticeable... I just noticed because I'm quite used to the car and driving it so I noticed the difference even tho it's very subtle...
For me I do believe when I have the new headers because they are cracked before the sensor ... the mix is not 100% and I need to correct the BISS after I get the new ones so I can get it properly dialed in ... I'm also going to be checking the IPS , and checking the base timings, if you know the VAQs for it I would highly appreciate it so I can do that on my day off I work around 50h per week so I barely have any time for this stuff, even during days off it's hard because I have so much to do from not being able to do it during the rest of the week...

Thank you very much for you help, it already gave me stuff to investigate
 
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