cylinder missfire
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From: Kenosha Wisc.
cylinder missfire
Hi, looking for some suggestions. I have a cylinder 8 misfire. Started intermittently and then became constant while driving in about a 5 minute timespan. Sets PO308. Swapped coils, plugs, plug wires, and injector. Pulled valve cover, springs look fine. Valve lift looks good. Compression is 155 psi. Leakage is 18%. Performed pressure drop test on all injectors, about 25 psi on all of them. No engine noise. No vacuum leaks. Using spark tester on all of the coils through the wires, spark is strong. Back probed the injector wires while running, signal looks good. I pulled the intake to look for carbon on the back of the valves, they are very clean. Has anyone seen a crank or cam sensor cause a single cylinder misfire? I don't have access to a scope. This is stumping me. Car is a 1998, all stock, 78K, Thanks for your suggestions in advance. Bill
Last edited by quik36; Aug 6, 2019 at 07:36 PM.
Burning Brakes
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From: Sacramento, California
Just guessing here, maybe there is a damaged wire on the #8 coil harness somewhere? When you swapped coils, plugs, plug wires and injector to #8 did the problem go away or did it continue to set P0308?
Steve
Steve
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Burning Brakes
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Steve
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Bill, Is this a misfire that you can actually feel or are you just getting a P0308 I'm guessing on your scan tool...what are your long term fuel trims look like right now ??
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From: Kenosha Wisc.
Definitely feel the miss. It’s there all the time. When I pull injector wires one at a time,8 is dead. I will check fuel trim when I get the intake back on. Other things I’ve tried. Using a OTC injector pulse tool, I can pulse that injector with no change to miss-fire. Makes me lean toward ignition but that checks out ok. That’s why I was wondering if the timing of the spark is off.
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Definitely feel the miss. It’s there all the time. When I pull injector wires one at a time,8 is dead. I will check fuel trim when I get the intake back on. Other things I’ve tried. Using a OTC injector pulse tool, I can pulse that injector with no change to miss-fire. Makes me lean toward ignition but that checks out ok. That’s why I was wondering if the timing of the spark is off.
and also make sure that the injector pintle valve is opening (picture enclosed)...you can pick up a single channel scope from AES Wave.com and I think it goes for around $300.00 or so I think. Good you did an injector balance test so you know all injectors are flowing properly.
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To all those who sent suggestions, thank you. Finally got back to the problem, when I removed the intake I found 1 of the wires to #8 injector rubber through. When I would unplug it to check for a signal, I would apparently move it enough to un ground it and it would check ok. Running great now!
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Verdad Gallardo
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From: Cape Coral, Florida
To all those who sent suggestions, thank you. Finally got back to the problem, when I removed the intake I found 1 of the wires to #8 injector rubber through. When I would unplug it to check for a signal, I would apparently move it enough to un ground it and it would check ok. Running great now!
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From: Kenosha Wisc.
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From: Cape Coral, Florida
It was the trigger wire. Apparently when I would unplug the injector and plug a “noid ” light in, I would move the harness enough and it would unground the wire and the noid would flash. After looking at fuel trims, the computer was trying to lean it out too. When I pulled the intake I found the rub through