3000GT VR4 Bogs down between 1500 - 3000 RPM

Hello all my name is Keith and live in Canada.

I have a 1994 Mitsubishi 3000GT VR4 and have been trying to work through an issue for the past 2 years.

Basically, between 1500 to 3000 RPM my car bogs down when under power and then above 3000 RPM it runs great.

I have completed the following to figure this out:

  1. Replaced or repaired all Vacuum Hoses and fixed all leaks - No change.
  2. Remove Plenum and Intakes and replaced all Gaskets - No change.
  3. Replaced Mass Air Flow - No change.
  4. Fuel Pressure & Pump tested - All good.
  5. Replaced Fast Idle Air Valve, IAC Motor & Throttle Position Sensor- No change.
  6. Re-wired Harness (crispy wires over Valve Cover) from MAF to Injectors - No change.
  7. Sent Fuel Rail & Injectors to specialist - increased flow by 22% - No change.

Codes come up in the Throttle Body and now looking to buy it??

Any help with this would be GREATLY APPRECIATED!!


Have you tried just cleaning the throttle body instead of keep throwing money at the car without diagnosis of the faulty part?
This is a common problem and should be easy to solve.

Have you tried a new PTU? Joe has an excellent video on it: Mitsubishi 3000gt / GTO PTU Removal - YouTube


Thanks Joe and I totally agree but it is at Mitsubishi now and they don’t repair anything anymore they just replace!!!

l am trying to get them to do some diagnostics and they keep coming back to the Throttle Body, IAC Motor, Fast Idle Air Valve & TPS.

As mentioned I have replaced all three but the IACM & TPS may have been an aftermarket version as the Mechanic never detailed the parts he bought and just wanted me to get my car out of their after 10 months and $4K and it was no better then when it started. I took him to small claims and got over half that back as he couldn’t provide any parts invoices!

The FIAV I bought at Mitsubishi so i know it is new and good. could there be any issue with the 3 not being from the same Throttle Body assembly?

Another person on your website here said to check the PTU and I looked at your video (which is excellent as always) and it might be an area to look at…do you agree!

The other area I would like to have checked out before buying more parts is the ECU…again, do you agree?

Any help would be appreciated and I am more then willing to pay for some of your expertise as if I don’t get this resolved, I have a 4,500 lb Anchor with a lot of new parts on it!!

Your Canadian friend,

Keith Andersen

Thanks Wes…that is interesting and something that hasn’t been brought up before.

I will see if we can go through the check and let you know!

Your Canadian friend,

Keith Andersen

Hi Joe:

Do you know of anyone that has a new ECU or can diagnose an existing one for my 1994 VR4?