Lately my truck developed this stumble. Its a 95 cpi W engine truck. It starts fine, idles good at first then it starts missing bad, then clears itself up. And when i drive it if im giving just a little gas like 1/4 pedel it starts surging and stumbling bad till i give it more gas then it clears up and doesnt come back untill its turned off and started again. What could this be? Its getting annoying.
Stumbles
Z400ryder87
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Lately my truck developed this stumble. Its a 95 cpi W engine truck. It starts fine, idles good at first then it starts missing bad, then clears itself up. And when i drive it if im giving just a little gas like 1/4 pedel it starts surging and stumbling bad till i give it more gas then it clears up and doesnt come back untill its turned off and started again. What could this be? Its getting annoying.
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96 Posts
The plugs arnt too old, but i did notice they burn weird ill try to get a pic of a plug tomorrow its hard to explain. I have not done a cap and rotor yet i probably should do that. Today the truck didnt stumble once, but it did it bad yesterday in the rain for some reason. I did notice my coil wire at night arching to the upper intake. The coil and wires are pretty new too i dont see why it would be doing this.
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I feel like its not the wire though because sometimes it looks like the coil itself is glowing. Like its leaking from there too, but the coil is pretty brand new, it did this with the old coil too.
if the old coil and the new one are showing the same thing then I would think more that it is the wire. Some dielectric could help to make sure that there is no moisture getting in. you can also mist the wires when it is running well and see if the fault comes back.
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I just put some dielectric grease on the coil wire tonight. The end goin into the dizzy looked to be kinda rusted. Im gonna end up probably doing new cap, rotor, and wires.
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What plugs do you guys run in your 4.3s?
OEM ac delco
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OK, I feel like this could be a fuel problem. Today I noticed the stumble seemed worse. Then I noticed when I turn the key to the on position the pump sounds like it doesnt prime everytime. Could this be the fuel pump takin a dump?
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check first by doing a fuel pressure test
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Ok, what should good fuel pressure be for a cpi engine?
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Havnt checked yet, gotta get it over to my buddies shop. It hasnt really stumbled alot lately its real weird how its acting. Once you rev it out past like 2000rpm the stumble stops and goes away and wont come back till the truck is shut off sitting for a little bit, then restarted to drive.
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I just borrowed my buddies guage and it was reading around 54psi. I might try a different guage I didnt really like his. But if this is the true reading is this good?
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8,792 Posts
Marginal, some say their rig runs good at that, some wont run at that, the pressure is only 1/2 the equation, you have to have adequate VOLUME as well, way to check that is to pull line into a bucket and time how long it takes to fill to X number of gallons. The manufacturers dont always quote the volume recomendations so yet again IDK. Have you changed the fuel filter?
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Yes filter is pretty much brand new. The truck hasnt been doing the stumble lately its odd. Seems to do it more when its wet out im starting to think its something electrical maybe.
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