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Thread: engine stutter

  1. #1
    FEP Power Member fgross2006's Avatar
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    Default engine stutter

    I have an 84 LX 5.0 with CFI.

    Overall the car runs great, Perfect idle. no codes when I scan, drives great.

    What I have noticed this summer is when i hit a bump the engine stutters, if I hit a patch of bumpy road the engine will stutter and the car bucks until I am driving on flat road again. Also I noticed that when i close the hood with the engine running the idle drops to almost stall then recovers.

    When I was troubleshooting an air conditioning issue last month I noticed I could sometimes make the engine stutter when touching the wire loom. So obviously I have a bad wire that effects the idle and is sensitive enough to complain when i hit bumps.

    I assume the only way to find the source is to pull off wire loom and separate wires and wiggle until I find the wire causing this issue. Has anybody else had an issue like this? Does it seem more likely the wiring to the fuel injectors or ignition?

    The stutter is the same symptom I got when my O2 wasn't grounded correct and earlier this summer when my ECT went bad. Neither of those are an issue now. No codes, car runs like a Swiss watch until I hot a bump, or close the hood.

  2. #2

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    Sounds like a bad ground honestly

  3. #3
    FEP Power Member fgross2006's Avatar
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    Quote Originally Posted by erratic50 View Post
    Sounds like a bad ground honestly
    sounds logical except that i just swapped the engine 2 summers ago and I meticulously cleaned every contact on the engine and in the engine compartment.

    It seems to stumble when I touch the wiring and also the connections going to the solenoid cluster on the driver side inner fender.

  4. #4

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    How is the insulation condition at the ignition module? Is it still a Duraspark? Those sat next to the exhaust manifold and basically cooked the insulation. Mine was rock hard and chipping off when I located the source of my stall on right hand turns. It's easy enough to check. Then put some electrical tape between the wires and test drive.
    W

    As always, "It ain't what you don't know that gets you, it's what you think you know that just ain't so."

  5. #5
    FEP Power Member fgross2006's Avatar
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    Quote Originally Posted by WilliamCapri View Post
    How is the insulation condition at the ignition module? Is it still a Duraspark? Those sat next to the exhaust manifold and basically cooked the insulation. Mine was rock hard and chipping off when I located the source of my stall on right hand turns. It's easy enough to check. Then put some electrical tape between the wires and test drive.
    I dont have a duraspark. I have a TFI and its relocated behind the front grille in a heat sink.

  6. #6
    FEP Super Member gr79's Avatar
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    Had similar with my EFI Ranger.
    Sudden stutter, even stall going over bumps. Flashing ck engine light. Finally no start. No codes.
    Dealer rewired something in the under hood fuse box but did not cure anything.

    Was fuel pump relay working loose 1/2 way out of its socket. Fuse box cover stopped it from coming out of socket.
    Kept coming loose. Pushed it back down in socket, good to go.
    Foam tape solved that. Filled gap above relay. Stopped relay from moving up to the fuse box cover.

    Then had ICM cause bucking, stall, shaking, tach bounce, no tach. Worse and worse. Failed the other day, prob heat.
    Weird part once warmed up, drove fine. Surely something else is amiss.
    The ICM wiring down there has a glitch too. Found a rubbed out bare spot in the wire insulation.
    Intermittent ground out of CKP. Temp fix with foil and tape. Still is not right. Can fault it moving harness.
    Does throw OBD I codes though not specific to the CKP or anything else but the ICM and coil packs.
    Installing good spare MC ICM today and test close to home. Have added extra ground leads from ICM screws to fender.
    It will function temporally un monunted and grounded, but gets hot of course without heat sink (bitch loc on intake manifold).
    Have read there is a TSB on the ICM wire connections. Not followed up yet. Dealer part costs and labor rates scare me.
    Last edited by gr79; 08-13-2019 at 02:13 PM.

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