Intermittent Misfiring Problem

[Chim55117]

So the VR-4 is back up and running, although I'm still experiencing a problem I had before. Sometimes, if I start the VR-4 up, it will be idling very rough, although there is no CEL. When this happens it sounds like the car is running on 3 cylinders. Any attempts to give the car gas make the car stall out. Now if I go to the passenger side and reset the ECU, sometimes it will start normally and drive fine. Sometimes I have to reset the ECU multiple times for this to happen. This happens on and off, sometimes after a reset the car will drive fine for a day, or even a week, then it will happen all over again. The ECU that I have has no leaking caps, and is running DSMLink V2.5. Has anyone experienced anything like this, or know what this could be? Is it possible that the MPI relay next to the ECU is going out? Thanks for your help in advance, this problem is making me somewhat afraid to take the VR-4 out due to the fear of it running rough randomly.

 

[Chim55117]

Anyone? I'd really appreciate some input!

 

[Terry Posten]

Start at the basics.

Replace the plugs and wires, clean your MAF, clean the TB and make sure the ISC is good, replace fuel filter. Do a general tune-up and see how she runs.

Make sure all the injector plugs and wiring are in good shape. When it starts running bad, pull 1 injector plug off at a time to figure out if you have an injector not firing. If you find a cylinder that does not affect the idle when the plug is removed, figure out if it is getting fuel into the cylinder or if there is no spark. Check the CAS and wiring.

Get back to us with an update after you have eliminated tune-up parts and simple wiring issues.

 

[Chim55117]

Plugs and wires are fresh. Injectors all work, if I pull any of them, the car starts to bog down even more, which is expected. CAS and wiring looks to be fine.

 

[SouthCaliVR4]

whats your data when the issue occurs, o2 voltage, mas readings, temp sensors ect. if it sound like it's hitting on three but wont isolate when killing one cyl at a time we need more detailed info. listing what you have done at the outset will help in determining what might be the next logical choice.

 

[Chim55117]

I think I may have solved this. I swapped the MPI relay next to the ECU with one from my brother's VR-4 and it started up right away at perfect idle. Drove it around town and it was fine. Could the old MPI relay have gone out or been failing?

 

[SouthCaliVR4]

Yes