Misfire after exhaust manifold replacement
12-12-2018, 03:35 PM
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Misfire after exhaust manifold replacement
Hi All,
I have a 2010 5.4 automatic. I just finished swapping the dreaded RH exhaust manifold.
I fired it up last night and it ran perfect. I drove it to work today and made it about a mile before it started skipping and misfiring.
This is how I did the swap.
Disconnected the battery a few weeks ago.
Removed the RH motor mount nuts
Lifted the engine on one side only using an engine hoist and a floor jack.
Removed the starter.
Dealt with all the crap associated with broken studs
Replaced with a new manifold, gaskets and hardware, reinstalled starter, starter gound strap and battery. I fired it up last night and it ran perfect.
I drove it this morning for the first time.
It ran great cold and started acting up as it got warm.
I pulled over and checked under the hood and noticed that the capacitors that bolt to the studs on the front of the cylinder heads weren't hooked up and one had a broken wire. As I moved the wire, it touched the head, sparked, and killed the engine.
I replaced the mini fuse under the hood for the coils and it started back up, but still ran rough.
It looks like I accidentally broke the wire for the capacitor for the RH cylinder bank and noticed that I forgot to reattach the LH capacitor to ground.
I took the truck home, fixed the wire on the RH head and bolted the LH to the cylinder head stud.
I am not sure if these affect the wiring or not,so I ordered a new RH capacitor.
The codes I am getting are misfire detected on startup, OBD readiness test not complete (assuming because the battery was disconnected for so long), cylinder 8 and cylinder 2 misfire detected.
The coils and plugs have maybe 300 miles on them and it ran fine before I started the exhaust repair.
Is it possible I damaged anything running the truck without the capacitors or by blowing the harness fuse?
More likely, is it possible I tweaked the intake manifold with the engine cranked up on one side?
Any input is appreciated.
I have a 2010 5.4 automatic. I just finished swapping the dreaded RH exhaust manifold.
I fired it up last night and it ran perfect. I drove it to work today and made it about a mile before it started skipping and misfiring.
This is how I did the swap.
Disconnected the battery a few weeks ago.
Removed the RH motor mount nuts
Lifted the engine on one side only using an engine hoist and a floor jack.
Removed the starter.
Dealt with all the crap associated with broken studs
Replaced with a new manifold, gaskets and hardware, reinstalled starter, starter gound strap and battery. I fired it up last night and it ran perfect.
I drove it this morning for the first time.
It ran great cold and started acting up as it got warm.
I pulled over and checked under the hood and noticed that the capacitors that bolt to the studs on the front of the cylinder heads weren't hooked up and one had a broken wire. As I moved the wire, it touched the head, sparked, and killed the engine.
I replaced the mini fuse under the hood for the coils and it started back up, but still ran rough.
It looks like I accidentally broke the wire for the capacitor for the RH cylinder bank and noticed that I forgot to reattach the LH capacitor to ground.
I took the truck home, fixed the wire on the RH head and bolted the LH to the cylinder head stud.
I am not sure if these affect the wiring or not,so I ordered a new RH capacitor.
The codes I am getting are misfire detected on startup, OBD readiness test not complete (assuming because the battery was disconnected for so long), cylinder 8 and cylinder 2 misfire detected.
The coils and plugs have maybe 300 miles on them and it ran fine before I started the exhaust repair.
Is it possible I damaged anything running the truck without the capacitors or by blowing the harness fuse?
More likely, is it possible I tweaked the intake manifold with the engine cranked up on one side?
Any input is appreciated.
Last edited by v8george; 12-12-2018 at 03:48 PM.
12-13-2018, 10:29 AM
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Problem solved
After doing a little reading, I decided to check the spark plug wells to check for moisture . From having the hood up in the rain, the spark plug wells had water in them. Since it's 20ﾟ out, when the truck is cold, it's ice . Once it ran for a few minutes the ice melts and shorts the coil. Blew them all out with air, cleaned the plugs and coils, truck runs mint!