V10 Excursion misfire problem
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V10 Excursion misfire problem
I have a 2000 Excursion with a V10 with 161000 miles. I have a misfire in the number 5 hole mainly when the truck is first started in the morning. No codes. The truck will run poorly but if you let it warm up and then turn it off and restart it, it runs perfectly for the rest of the day. If you don't shut it off, it will run poorly all day long. This has even the best mechanics in my area stumped. Here is a list of things we have done.
All new plugs and coil packs We even did the plugs twice
crank position sensor
Idle Air control motor
Mass Air Flow sensor
PCM
What could possibly cause 1 hole to misfire if its not the plug or COP? The first time we changed the plugs and COP, there was a little bit of oil in the number 5 spark plug well, but even after changing it, it did the same thing. Why after turning off and then restarting it would the misfire go away? Could it be a fuel issue instead? Everybody I've taken it to is convinced its spark/electrical. Any input will be appreciated.
All new plugs and coil packs We even did the plugs twice
crank position sensor
Idle Air control motor
Mass Air Flow sensor
PCM
What could possibly cause 1 hole to misfire if its not the plug or COP? The first time we changed the plugs and COP, there was a little bit of oil in the number 5 spark plug well, but even after changing it, it did the same thing. Why after turning off and then restarting it would the misfire go away? Could it be a fuel issue instead? Everybody I've taken it to is convinced its spark/electrical. Any input will be appreciated.
Fleet Mechanic
Joined: Feb 2011
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From: Thousand Oaks, CA
I have a 2000 Excursion with a V10 with 161000 miles. I have a misfire in the number 5 hole mainly when the truck is first started in the morning. No codes. The truck will run poorly but if you let it warm up and then turn it off and restart it, it runs perfectly for the rest of the day. If you don't shut it off, it will run poorly all day long. ....
What could possibly cause 1 hole to misfire if its not the plug or COP? The first time we changed the plugs and COP, there was a little bit of oil in the number 5 spark plug well, but even after changing it, it did the same thing. Why after turning off and then restarting it would the misfire go away? Could it be a fuel issue instead? Everybody I've taken it to is convinced its spark/electrical. Any input will be appreciated.
What could possibly cause 1 hole to misfire if its not the plug or COP? The first time we changed the plugs and COP, there was a little bit of oil in the number 5 spark plug well, but even after changing it, it did the same thing. Why after turning off and then restarting it would the misfire go away? Could it be a fuel issue instead? Everybody I've taken it to is convinced its spark/electrical. Any input will be appreciated.
What are you using to determine it's #5 that's misfiring?
The PCM grounds the coil/injector lines to complete the circuits. Check that the PCM case to chassis grounds are good.
What voltage is on the #5 coil/injector lines compared to another cylinder when the ignition switch is turned to RUN?
What voltage is on the #5 lines at the PCM connector? Maybe a wire is down to 1 or 2 strands.
Fleet Mechanic
Joined: Oct 2017
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From: Southwest Ohio
I’d check the compression of the cylinder and compare it to at least two other cylinders. My experience is when a misfire goes away after the engine heats up is that there is a piston ring sealing issue.
— Dave
— Dave
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I’ve been told compression is good. It runs bad until it warms up, but to get it to run right you must turn of the engine and restart it. That leads me to believe it’s something electrical. There are even some days that it runs ok even from the first start but not very often. So it seems like it’s something that resets.
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To the first reply, they determined #5 to be the culprit using a snap on scanner/computer. I can’t answer any questions about voltage. I don’t have the ability to check that and I don’t think anyone has checked that.
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