Zeleske
New Member
- Joined
- November 22, 2014
- Messages
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- Year, Model & Trim Level
- 99 5.0L Explorer
Hi all, I've gotten help too many times to count by reading other posts in this forum, but now I'm stumped.
5.0L '99 Explorer, 219k
I have misfires on cylinders 2 and 3. The fuel trim is quite high on bank 1 (where the misfires are) - hovers in the 20's consistently, I've seen it as high as the 40's in the cold with some gas. Bank 2 stays well centered around zero.
What would cause such a high fuel trim on bank 1? With the fuel trim history cleared, and fresh spark plugs it seems to run fine until the trim rises and then it seems to misfire rich.
Here's what I've been through so far:
New plugs
New plug wires
Destroyed a coil pack while goofing around, so a a new coil pack too
Then called a buddy certified master mechanic who throws out ideas without much action:
Compression check passed
Fuel pressure was in spec
Spark check was weak, plug seemed fouled. A new plug sparked strong for a short time until it got fouled by so much fuel
Replaced upper and lower intake manifold gaskets
Today I switched the upstream O2 sensors between bank 1 and bank 2 (thanks to the post about pulling the center console), problem stayed on bank 1 - so not the O2 sensor.
I'm stumped. All I'm thinking is that maybe that lower gasket didn't go on quite right, or there is another vacuum leak somewhere that would touch only bank 1?
5.0L '99 Explorer, 219k
I have misfires on cylinders 2 and 3. The fuel trim is quite high on bank 1 (where the misfires are) - hovers in the 20's consistently, I've seen it as high as the 40's in the cold with some gas. Bank 2 stays well centered around zero.
What would cause such a high fuel trim on bank 1? With the fuel trim history cleared, and fresh spark plugs it seems to run fine until the trim rises and then it seems to misfire rich.
Here's what I've been through so far:
New plugs
New plug wires
Destroyed a coil pack while goofing around, so a a new coil pack too
Then called a buddy certified master mechanic who throws out ideas without much action:
Compression check passed
Fuel pressure was in spec
Spark check was weak, plug seemed fouled. A new plug sparked strong for a short time until it got fouled by so much fuel
Replaced upper and lower intake manifold gaskets
Today I switched the upstream O2 sensors between bank 1 and bank 2 (thanks to the post about pulling the center console), problem stayed on bank 1 - so not the O2 sensor.
I'm stumped. All I'm thinking is that maybe that lower gasket didn't go on quite right, or there is another vacuum leak somewhere that would touch only bank 1?