Missfiring
#1
Missfiring
I was heading to work one morning and about a mile in to my drive the truck started cutting out. I pulled in at work and it idled fine, but would still cut out when getting in to the gas. It did this the next two times I drove it. First thing I did was checked vacuum. Checked out at around 16-18, so that’s fine, so I moved on to checking missing cylinders. I pulled off plug wires one by one and found out the rear cylinder didn’t care if it was plugged in or not. I put on new plug wires and plugs and fired it up. It then had a miss at idle and under power. What the hell. A friend at the shop suggest it’s a vacuum leak and I laughed and said it was the first thing I tried. He sprayed break cleaner over the lines and intake and it revved up. Turns out when I was changing the plugs I plucked off a vacuum line from throttle body to the EVAC. Plugged the throttle body with my finger and it ran fine. Cool beans, right? Well after I replaced the hose with new a new line it still has misfires at idle and at speed. I can now pinch off the hose at the throttle body and it doesn’t help the truck run right.
Other things I did,
Replaced fuel filter, super dirty gas came out. Almost muddy, filter nearly clogged.
Checked front and rear injectors, both tested 14.7Ohms
Back probed the MAF sensor and it read 1.2V at idle and 2.2V around 3K RPM, also doesn’t care if I put my finger in front of the MAF sensor. Unplugging it and plugging it back it doesn’t matter either.
The truck isn’t throwing any codes out, and I bought a Chiltons manual so I’d be able to check sensors myself on the truck. But oh no, Chiltons doesn’t list any parameters for the sensors, just a how to on replacing them. Thanks, but no thanks Chiltons, I can handle that part.
Any suggestions would be helpful at this point.
Other things I did,
Replaced fuel filter, super dirty gas came out. Almost muddy, filter nearly clogged.
Checked front and rear injectors, both tested 14.7Ohms
Back probed the MAF sensor and it read 1.2V at idle and 2.2V around 3K RPM, also doesn’t care if I put my finger in front of the MAF sensor. Unplugging it and plugging it back it doesn’t matter either.
The truck isn’t throwing any codes out, and I bought a Chiltons manual so I’d be able to check sensors myself on the truck. But oh no, Chiltons doesn’t list any parameters for the sensors, just a how to on replacing them. Thanks, but no thanks Chiltons, I can handle that part.
Any suggestions would be helpful at this point.
#2
Check your work a bit closer. Do the test to determine which cylinder is not working properly, and then check the plug & wires by swapping one at a time with the neighbor plug/wire. If the misfire follows the swap, that part is defective.
Given your description of the filter contents, you may have stirred up some 'gunk' and it got pumped to the injectors, possibly plugging one. I think they have very small screens as the last resort filter, and they can be cleaned but you have to remove the fuel rail for access to the injector inlet.
You might also want to take a look at the MAF internals, two wires, as if they get coated with 'stuff' they won't work right, and you'll get hesitation and possible misfire on acceleration.
tom
Given your description of the filter contents, you may have stirred up some 'gunk' and it got pumped to the injectors, possibly plugging one. I think they have very small screens as the last resort filter, and they can be cleaned but you have to remove the fuel rail for access to the injector inlet.
You might also want to take a look at the MAF internals, two wires, as if they get coated with 'stuff' they won't work right, and you'll get hesitation and possible misfire on acceleration.
tom
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