help diagnosing 4.6 miss fire with no code
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6th Gear
Joined: Dec 2020
Posts: 6
Likes: 0
From: Ohio rust belt
help diagnosing 4.6 miss fire with no code
Hi all, I have a 1999 4x4 m5r2 f150 with the 4.6, it has had a crazy multiple cylinder miss fire going for over a month with no misfire code and I really am having a hard time figuring it out. So here's what I do know, The engine has 256k on it and was running fine until I got off the highway one day. when the engine is cold or hasn't ran in a couple hours it will run fine. the miss fire doesn't start until the engine reaches operating temp and only seems to miss fire under load. I shot the parts cannon at it at first just thinking it needed plugs, the wires are only about 2 years old and look good, and I threw coil packs on there too for good measure. Still miss fired. I checked fuel pressure on the rail and it was wonky so I threw a filter and new pump in it. still miss fired. I've deep cleaned the throttle body, checked the grounding on the coil packs, removed and cleaned mass air sensor, checked for vacuum leaks. basically short story long I'm running out of ideas. Any help is greatly appreciated, Thanks!
Last edited by fsd7.3idi; Oct 5, 2022 at 08:20 AM.
Hotshot
Joined: Jul 2020
Posts: 10,453
Likes: 2,630
From: Near Salt Lake City
I would put new fuel injectors in it
I would do several other things first
Like, running it around with the MAF disconnected
And, driving it around with a fuel pressure gauge taped to the windshield
Clear codes and retest, several times, looking for some code other than just P0300
I would do several other things first
Like, running it around with the MAF disconnected
And, driving it around with a fuel pressure gauge taped to the windshield
Clear codes and retest, several times, looking for some code other than just P0300
Thread Starter
|
6th Gear
Joined: Dec 2020
Posts: 6
Likes: 0
From: Ohio rust belt
I would put new fuel injectors in it
I would do several other things first
Like, running it around with the MAF disconnected
And, driving it around with a fuel pressure gauge taped to the windshield
Clear codes and retest, several times, looking for some code other than just P0300
I would do several other things first
Like, running it around with the MAF disconnected
And, driving it around with a fuel pressure gauge taped to the windshield
Clear codes and retest, several times, looking for some code other than just P0300
Tuned
Joined: Jul 2022
Posts: 333
Likes: 60
I would put new fuel injectors in it
I would do several other things first
Like, running it around with the MAF disconnected
And, driving it around with a fuel pressure gauge taped to the windshield
Clear codes and retest, several times, looking for some code other than just P0300
I would do several other things first
Like, running it around with the MAF disconnected
And, driving it around with a fuel pressure gauge taped to the windshield
Clear codes and retest, several times, looking for some code other than just P0300
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