03 Driver Bank Misfire Issues

Discussion in 'SRT10 and SRT10 Coupe Discussions' started by Darrah, Jul 4, 2018.

  1. Darrah

    Darrah Enthusiast

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    I've been lurking the forums for some time now while in process of finding/purchasing my Viper. Now that I've had the car a few months, I've run into an issue that I'm hopeful you guys can help with. Sorry for the length, but I'm trying to give as much info as possible.

    The car is an '03 with intake, headers, corsa track exhaust, and tune. It ran perfectly fine for over a month, and then started to develop a misfire issue. At first, it would run fine for the first 5 minutes, and then start to misfire for a mile or two, and then clean up and run fine for the remainder of any drive. As time has gone on, the issue has become worse to the point that it now is happening pretty much constantly. When it happens, the driver's side bank of cylinders more or less stops firing. You can feel a distinct difference in the exhaust pressure pulses on the driver's side, and it will pop and pulse as it fires/misfires, unlike the smooth/rhythmic output of the passenger side. Similarly, when driving and it happens the driver's side exhaust goes almost completely quiet while the passenger side is still smooth/loud. It'll cut in and out of this state occasionally... run fine for a second or two, then cut out for a few seconds, then back in, etc... which results in the car feeling like you're stabbing the gas on and off.

    When the car is having this issue, if I let off the gas it'll backfire out the driver's side exhaust and then usually start firing, but once I try to accelerate it'll cut out again. It's an odd sensation to have one ear hearing cylinders firing and the other pretty much complete silence

    As a little background, I'm an industrial mechanic/electrician by trade and have been restoring Mopar muscle cars my whole life. So I'm mechanically experienced, but dealing with a performance fuel injected car is pretty new. All the plugs are brand new and I've pulled and reseated all the wires multiple times with little effect. The problem also persists regardless of stock/aftermarket tune.

    Is there a sensor, wire, ground, anything that will impact only the driver's side cylinders? I was thinking a coil going bad, but neither of them are limited purely to the driver's side. I tried running it in the dark and looking for some arc jumping, and didn't see any evidence of that either. Any ideas on what to start chasing?

    Thanks for any help/ideas you may have.
     
  2. Steve-Indy

    Steve-Indy VCA Venom Member - Great Lakes

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    Sorry for your troubles.

    How many miles?

    Check engine light?...If yes, what are codes?

    Have you looked at O2 sensor wires? They are often fried with headers.

    Plugged cat?

    Checked plugs to PCM?
     
    Last edited: Jul 4, 2018
  3. Darrah

    Darrah Enthusiast

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    53,000 miles. If I load the stock tune it’ll throw an 02 code, which I expected to see, but zero cel if I have the aftermarket tune. No cats, so shouldn’t be an issue there. I was thinking possibly O2 wires but haven’t had a chance to dig into their location and inspect. I’m assuming once I take the heat shield off it’ll be visible? Just checked the PCM plugs this afternoon and they seemed good
     
  4. Steve-Indy

    Steve-Indy VCA Venom Member - Great Lakes

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    Thanks...checking wires on O2 sensors certainly worth doing.
     
  5. ViperJeff

    ViperJeff VCA Legacy Member - UT/AZ Staff Member

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    First thing that came to mind with the mods you have is a faulty 02 sim
     
  6. Darrah

    Darrah Enthusiast

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    I'm going to try to did into the O2 sensors tomorrow if I can get some time. I went ahead and replaced the coils/wires due to a couple mismatched plug wires from the previous owner (assuming they burned up a few). The car ran great for about 1/4 mile then back to misfiring, and still only on the driver's side. My thoughts now are O2, cam or crank sensor, or pcm. After looking at the service manual, I see all the driver's side injectors are powered by a common wire... so an issue with that could explain it also. Noid light should make that obvious pretty quickly.

    If I can dig into it tomorrow I'll share the rresults. Ialso have a video of it misbehaving I'll try to post
     
  7. Darrah

    Darrah Enthusiast

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    Pulled the side skirt off this morning. No O2 sim, they just zip tied the secondary O2 up out of the way. The primary O2 has been extended and routed out of the way but the wrap is brittle so I’m sure it has gotten hot. Once I get a free day I’ll unwrap/inspect and repair if necessary. Nothing looks too bad though, which is discouraging.
     
  8. Darrah

    Darrah Enthusiast

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    YouTube link. This was before replacing coils and wires, when it was at its worst. It has gotten better since this video but still sporadically misses while idling or revving and borderline undrivable under load

     
  9. Darrah

    Darrah Enthusiast

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    O2 wires checked out good. Also disconnected both upstream and downstream on driver's side and didn't change in the slightest. As an update, the car does in fact have cats. They installed high flow cats just after the headers that I wasn't aware of until I pulled the sills today.
     
  10. MoparMap

    MoparMap VCA National President

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    If it's just the one bank I would certainly think it's likely injector or coil based. Since the coils aren't unique to a bank based on what you were saying, the injectors would be the next place I'd look. Not sure where the power/ground feed for the bank splices out of the harness, but if it's a common point there could be a break in it that's interrupting power to the whole bank. Otherwise pretty much every system is tied between banks, so not isolated as far as I'm aware.

    It would suck, but the other option could be a bad power transistor in the ECM. My dad had a 92 Stealth that had a bad fuel pump transistor. If you hot-wired the pump constant on it would run fine, but otherwise the ECM wouldn't keep it running. Not nearly as easy to diagnose, but if you've got an oscilloscope you could try watching one of the injectors on the bad bank and see what you get. If you've got an analog multimeter you might be able to just watch for twitches. If it's twitching consistently then it might be okay, but if it goes dead intermittently I would suspect a bad wire or transistor.
     
  11. Darrah

    Darrah Enthusiast

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    Looks like it's injector related, probably in the harness as some have mentioned. I replaced the cam and crank sensors since they're relatively easy, which didn't make a difference (didn't think it would). I then hooked up a noid light on #5 cylinder and it was pulsing as expected, so I hooked the injector back up and the car started running normally. I took it down the driveway and it started missing again. Pulled it in the garage, unhooked all the driver's injectors and then hooked them up again, car started running normally. Took it for a 20 minute drive, the first time I've been able to for weeks, and it ran perfectly fine. Seems like everytime I mess with the injectors or injector harness the problem is impacted, so at least it's getting narrowed down.
     

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