2G Euro Eclipse 4G63 N/A Stalling at Idle when MAF is plugged in

[sunovermoon]

Hey everyone! I recently purchased a fully stock EDM 4G63 N/A Eclipse GS which had some issues:

MAF plugged in - the car constantly stalled at idle
MAF not plugged in - very rough idle and lack of power (FIXED with a new fuel pump)

Took it to a former Mitsubishi electrician who concluded it must be either an MAF or ECU issue. I tested a new working MAF, which didn't solve the stalling. IAC and BISS were checked. No vacuum leaks.

Could it really be I need the new ECU? If I do, is it a plug-and-play or will I need to program it to the car?

Thank you!

 

[pauleyman]

IAC and BISS were checked how? Did you set idle per factory procedures?
Yes ECU can be a problem but rule out the obvious first.

 

[sunovermoon]

IAC and BISS were checked how? Did you set idle per factory procedures?
Yes ECU can be a problem but rule out the obvious first.

Correct, checked and set with the proper equipment to factory numbers.

 

[pauleyman]

Correct, checked and set with the proper equipment to factory numbers.

I would at least give the ECU a visual inspection. If there is damage it may be obvious. I would also check the ISC coils for proper range and if possible do it under operating conditions. Blow a hair dryer on it or something. If ISC coils blow, it can also damage the drivers in the ECU.
If you're sure there are no vac leaks there isn't much left.

 

[sunovermoon]

Thanks for the reply!

Will verify all that, I'll report back.

 

[dwb]

Unplugging the MAF puts it into limp mode and the ECU no longer calculates airflow. If it runs worse with it plugged in it's likely you have a source of unmetered air, AKA vacuum leak. It would be worth double checking all your vacuum lines and/or doing a smoke test if you have any doubt in your previous diagnosis.

 

[sunovermoon]

Unplugging the MAF puts it into limp mode and the ECU no longer calculates airflow. If it runs worse with it plugged in it's likely you have a source of unmetered air, AKA vacuum leak. It would be worth double checking all your vacuum lines and/or doing a smoke test if you have any doubt in your previous diagnosis.

I do trust the diagnosis, but I will still verify with a smoke test. Better to be safe than sorry!

 

[pauleyman]

Was it verified the throttle is actually closing both physically and the ECU is getting a closed throttle signal from TPS?

 

[motomattx]

You really need a way to view the data stream in the car, your fuel trims wold tell you if you have a vacuum leak or if your airflow meter is working properly without the guesswork.

 

[sunovermoon]

Update to his: Still no fix so far.

I tested further, and I'm 100% sure it's not a vacuum leak. I sourced a new ECU, which did not fix the issue. The car was even stripped and every single inch of cable was checked, just because you never know

Even though I tested with another MAF, which I was told was supposed to be working, my only conclusion is that it is just a MAF issue and I got unlucky with both being bad.

Need to find someone who has a running one around me and swap it on the spot. It's impossible to find new OEM MAFs for reasonable prices. Does anyone know if there's another brand that will work plug and play?

 

[FIBA M - EC17PSE]

It may help but i have an oem Brand spanking new one sitting in my spares box i am selling! Its not in a box from mitsu. Likely one of the rare oem new units kicking about the place

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Im in the UK. I collect so much stuff