Missfire from hell
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Missfire from hell
Excursion people, please help!!
If anyone has advice please help. I had a horrible miss on my 6.8. Cylinders 4 and 9 were showing no change in idle when I removed the coil or injector clip. Problem started when driving uphill for a long distance and it turned into a gutless pig. Changed plugs to MC plugs and new MC coils and boots on both cylinders. No change. Swapped plugs and coils several times with other cylinders hoping it would migrate, no dice. Compression dry and wet shoes 0 on cylinder 9 do I pulled the heads and had them machined. Heads are in. 10 new plugs, 10 new coil packs. Same miss on 4 and 9. I believe the pcv is bad because there is more oil than I’d like in the intake manifold so I’ll replace that in the morning. The heads were all fine when removed with the exception of carbon built up on the valves. Fuel pressure at idle is 35 and drops to 30 with the key on and motor not running. Any suggestions here would help greatly. The block and pistons were inspected when the heads came off and I cpildnt see anything except a little carbon on the top of the piston heads. Miss on 9 is -49 and miss on 4 is -28.
If anyone has advice please help. I had a horrible miss on my 6.8. Cylinders 4 and 9 were showing no change in idle when I removed the coil or injector clip. Problem started when driving uphill for a long distance and it turned into a gutless pig. Changed plugs to MC plugs and new MC coils and boots on both cylinders. No change. Swapped plugs and coils several times with other cylinders hoping it would migrate, no dice. Compression dry and wet shoes 0 on cylinder 9 do I pulled the heads and had them machined. Heads are in. 10 new plugs, 10 new coil packs. Same miss on 4 and 9. I believe the pcv is bad because there is more oil than I’d like in the intake manifold so I’ll replace that in the morning. The heads were all fine when removed with the exception of carbon built up on the valves. Fuel pressure at idle is 35 and drops to 30 with the key on and motor not running. Any suggestions here would help greatly. The block and pistons were inspected when the heads came off and I cpildnt see anything except a little carbon on the top of the piston heads. Miss on 9 is -49 and miss on 4 is -28.
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From: geary NB
if your stil recieving missfire or totaly nothing from those 2 id pull the harness and check check for any broke or burnt wires that might be bleeding the electicity to somethign near by i had this kind of issue on cylinder 5 with a wire grounding to the AC line and causing a misfire that gave the appearence of a bad coil
Fleet Mechanic
Joined: Feb 2011
Posts: 1,812
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From: Thousand Oaks, CA
Do you get 12v with ignition switch in Run at the coil and injector connectors, coils - RD/LG, injectors - RD?
Do you get 12v at the PCM connector (C175), #4 - coil YE/BK (102), injector BB/LB (100) , #9 - coil WH/RD (82), injector GY/BK (42)?
(The wire colors are for a 2002, probably the same.)
Fleet Mechanic
Joined: Feb 2011
Posts: 1,812
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From: Thousand Oaks, CA
Interesting the misfires are on consecutive firing order cylinders.
There's a similar issue on the V10 forum with 2 consecutive cylinders misfiring - https://www.ford-trucks.com/forums/1...2-and-7-a.html
There was another thread like this about a year ago.
There's a similar issue on the V10 forum with 2 consecutive cylinders misfiring - https://www.ford-trucks.com/forums/1...2-and-7-a.html
There was another thread like this about a year ago.
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notes on the issue:
-the heads were removed and neither one shows anything abnormal.
-injectors have been swapped and the plug on 9 comes out wet
- miss goes away at higher rpm and live data shows it’s not a “no fire” only low contribution. No load it goes away at 2k. Under load it goes away at 3.5k
-fuel pressure was spot on with key on, idle and WOT.
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Cargo Master
Joined: Apr 2013
Posts: 3,087
Likes: 24
From: Central Florida
Brofessor,
are you sure it isn’t the other side of the head? I’ve seen a few issues on this forum where an engine loses a follower/lifter goes bad.
I hope you checked out this stuff during the previous disassembly.
And youre right to focus focus on the low compression first.
Im very impressed you’ve removed and reinstalled the heads even once. I wouldn’t tackle that job even without my back pain.
are you sure it isn’t the other side of the head? I’ve seen a few issues on this forum where an engine loses a follower/lifter goes bad.
I hope you checked out this stuff during the previous disassembly.
And youre right to focus focus on the low compression first.
Im very impressed you’ve removed and reinstalled the heads even once. I wouldn’t tackle that job even without my back pain.
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Cargo Master
Joined: Mar 2011
Posts: 2,066
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From: North Texas
It is amazing how well these run on 9 cylinders at the higher RPM's. How many miles are on this engine? I would be inclined to buy a complete reman longblock rather than mess with heads on a higher mileage lower end.
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motor has 220 on it. Not knocks or ticks anywhere in it. When the heads were off it was the perfect excuse to replace the sealing oil pan leak. Visual inspections show no signs of concern anywhere in the lower end.
the heads on the v10 are not as bad as they are made out to be. I have previously done the egr delete so that takes the headache away from the driver side and all exhaust bolts were intact. Driver side head will be about 3 hours in and out. The secret is to ziptie the head bolts up once removed so you can remove the heads without pulling the motor or can. Book time for both shows 21 hours but 8 hours with experience seems about right.
rockers, cam lobes, springs and seats were all inspected and look right. The leak could be within a runner or somewhere not visible to the eye. I will update again after the new head comes in in a few days.
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