Results 1 to 10 of 23

Thread: Misfire under accel, right bank rich - left is lean

Hybrid View

Previous Post Previous Post   Next Post Next Post
  1. #1

    Default Misfire under accel, right bank rich - left is lean

    My car has been running pretty good up until last week. When I tried to do a burnout it acted like I had traction control (bogging the engine down) so I went to pull away and had a dead cylinder. Got it home and cylinder 8 had a totally open circuit spark plug wire. Also checked the plug and it still appeared good. Put a new wire on and all was good, ran fine, idled good. The next day went to drive it and got a couple blocks away, had the misfire/dead cylinder again (same side of the engine). Got around to checking the wires today and all are good.

    When cruising at one speed the engine runs good, a/r ratios match on each side.
    While accelerating the left side is considerably leaner.

    In my mind either the left side has an issue with a fuel injector not firing or partially plugged, or the right side has a poor spark that is getting blown out under a load.

    Does MSD have any way of letting us look into the efi system with a laptop or data log to get more information?

  2. #2


    I swapped the drivers and passenger side coils, ohmed out all the spark plug wires, installed new plugs, ohmed out the two coil pack harnesses, have proper voltages and grounds going to them too. Did a compression test while the plugs were out, 175-190 psi. Car still runs like crap.

    Is there any way of forcing the injector to pulse one at a time with the MSD setup? On my last project car I could do almost anything with the efi system it had (disable spark plugs, change firing order, force the outputs one at a time...)

    I am still not sure what is happening, either the drivers side has a fuel delivery issue (the fuel pressure is constant though) or the passenger side has a spark/ignition issue.

  3. #3


    Swapped drivers side and passenger side fuel injectors this morning, still have the same issue. The issue starts about 60 seconds after initially starting the engine during warm up. Called MSD and they said there is nothing else I can do with it, have to send it in for testing so I got the RMA and address.

    FYI, these units are non-repairable. One person I talked to on the phone said they can sell me which ever item has failed, the other person said they can't. I am hoping when we know which piece has failed that we can get just one replacement part.

  4. #4


    Joe, have you got this resolved?

  5. #5


    That is a negative. Talked with MSD support and they said that everything I already tried and tested was all I could do and to further look into it the system will have to be shipped to Texas. They should have received it August 11th or 12th. I am still waiting on a response back from them, as far as I know they have not looked at it yet.

  6. #6


    To update everyone, MSD tested the unit and it doesn't look like they found anything wrong (at least its not mentioned on the paperwork). I have since installed a different EFI system and it appears to have the same issues with randomly running lean on the drivers side of the engine. I have tried to find vacuum leaks with carb cleaner, brake clean and propane with no luck. I am starting to think about pulling off the intake manifold and checking the seals on it, perhaps look for cracks or a broken fitting at the back of it.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
About us
Holley has been the undisputed leader in fuel systems for over 100 years. Holley carburetors have powered every NASCAR® Sprint® Cup team and nearly every NHRA® Pro–Stock champion for four decades. Now, Holley EFI is dominating the performance world as well as our products for GM's LS engine. Holley's products also include performance fuel pumps, intake manifolds & engine dress–up products for street performance, race and marine applications. As a single solution, or partnered with products from other Holley companies - Hooker Headers, Flowtech Headers, NOS Nitrous, Weiand, Earl's Performance Plumbing, or Diablosport - Holley products can give you the edge you need over the competition.
Join us