1996 F150 4.9L Cylinder 6 misfire
#1
07-17-2013, 05:30 PM
1996 F150 4.9L Cylinder 6 misfire
My truck had been throwing an 0420 code for about a year and I was just clearing the code. Then last month I was taking the thing from Milwaukee to South Dakota on a hot day last month.
Climbing the bluff on the Minnesota side of the Mississippi river, my daughter and I noticed the smell of melting plastic. Shortly thereafter, the check engine light started blinking. I pulled over and the code said that cylinder 6 was misfiring. Under the hood I found the top of the diverter valve was melted away as was part of the exhaust hose barb on the DV. I fixed the DV as best I could with some high-temp caulk and a piece of brass and we continued on, but the thing continued to misfire on cylinder 6 all the way out to SD and back.
Some Notes:
- It does not misfire when the engine is cold. Even after the thermostat opens, it does not misfire for several more minutes.
- It is not compression.
- I replace the plugs, wires, distributor cap and rotor. No effect.
- I checked the EGR valve by plugging the vacuum line to it. The truck threw an 0174 (fuel too lean) and a 0401 (DPFE) code but the problem persisted.
- I replaced the two upstream O2 sensors which seems to have eliminated the 0420 codes I was getting, but did not eliminate the problem.
- I replaced the defective diverter valve.
- I am getting spark at the number 6 cylinder.
Is the problem the injector? How can I test that? I have never had an engine-temperature-related problem with an injector before. Is that common?
I love this truck. When it is not misfiring is runs like the day it rolled off the factory line.
Climbing the bluff on the Minnesota side of the Mississippi river, my daughter and I noticed the smell of melting plastic. Shortly thereafter, the check engine light started blinking. I pulled over and the code said that cylinder 6 was misfiring. Under the hood I found the top of the diverter valve was melted away as was part of the exhaust hose barb on the DV. I fixed the DV as best I could with some high-temp caulk and a piece of brass and we continued on, but the thing continued to misfire on cylinder 6 all the way out to SD and back.
Some Notes:
- It does not misfire when the engine is cold. Even after the thermostat opens, it does not misfire for several more minutes.
- It is not compression.
- I replace the plugs, wires, distributor cap and rotor. No effect.
- I checked the EGR valve by plugging the vacuum line to it. The truck threw an 0174 (fuel too lean) and a 0401 (DPFE) code but the problem persisted.
- I replaced the two upstream O2 sensors which seems to have eliminated the 0420 codes I was getting, but did not eliminate the problem.
- I replaced the defective diverter valve.
- I am getting spark at the number 6 cylinder.
Is the problem the injector? How can I test that? I have never had an engine-temperature-related problem with an injector before. Is that common?
I love this truck. When it is not misfiring is runs like the day it rolled off the factory line.
#2
09-07-2013, 03:31 PM
#3
09-07-2013, 11:46 PM
It sounds like the ignition control module on the fender or the PIP sensor in the distributor. It could also be a vacuum leak, or the MAF sensor.
Check your fuel pressure. A lean condition will occur if the pump is weak, also it could be a bad fuel filter. I had this happen on my '96 with a 300ci six in it. The filter was full of rust and water, replaced it and my lean code and poor running went away.
Check your fuel pressure. A lean condition will occur if the pump is weak, also it could be a bad fuel filter. I had this happen on my '96 with a 300ci six in it. The filter was full of rust and water, replaced it and my lean code and poor running went away.
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