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My truck has an ongoing problem that I haven't been able to figure out. Any help from those with experience would be appreciated.
I have a 2001 F-150, 5.4L Bi-fuel GFI factory installation with 94,000 miles. The truck is in excellent condition for the mileage and starts, idles and runs great on both gasoline and CNG. The truck was previously owned by Southwest Gas in Phoenix, and I bought it last November.
About three weeks after buying the truck I was driving on the freeway in a heavy rain and started to notice an intermittent jerk, like a hard shift. I could tell something was wrong, so I stopped and switched over to gasoline and it ran perfectly.
In the days that followed, I determined that the truck ran without problems at speeds under about 40-45 mph (great for in town), but when lightly accelerating at speeds from about 50-65 mph it would buck/jerk. The transmission is not shifting, because I can feel the transmission shift normally and notice the change in rpms, and this buck is something different.
The buck/jerk happens only when driving on CNG.
To describe what I am calling a buck/jerk, imagine that you are towing someone with a chain and the chain comes tight after having a little slack in it. I also hear a noticeable "clunk" sound coming from the engine.
About three weeks later, and after experiencing probably 20 of these clunks, my #3 spark plug ejected. After a lengthy repair of the spark plug threads using the Time-Sert Ford Triton #5553 kit, I replaced all of the coil-on-plugs, spark plugs, seals and o-rings.
After firing it up, I did a vacuum test and the needle held steady at 18 in/Hg (elev 2,500 ft) and behaved correctly under sudden acceleration, etc. The vacuum did not hold after shutting the engine off (I don't know if it is supposed to).
I test drove the truck under all conditions and blasted up hills on the freeway at top speed with tons of power and no bucking or hesitation. I was elated! About three days later I felt my first buck.
Drained the coalescent filter again, and filled the housing with 90% isopropyl alcohol--drove about 50 miles and felt a buck.
Unsealed the tuning screws and returned them to the neutral position. The driver side screw was turned down at least three full turns fully sealed; that didn't seem right. After checking the high state O2 readings as specified in the manual, the neutral screw settings seemed to be giving good readings. This time I drove the truck for about 100 miles on the freeway before I felt a buck.
Today I finally received the correct coalescent filter element and I changed that out. When I drive the truck to Salt Lake this weekend, I fully expect to feel a buck and end up driving 80% of the way on gasoline.
My next step is to either sell it to some unsuspecting fool (I don't know if my conscience will allow that) or install a TechnoCarb system.
Sorry about the long post, but this has consumed the last 4 months of my life and I had to get it off my chest. Please help if you can.
Samuel
I have a 2001 F-150, 5.4L Bi-fuel GFI factory installation with 94,000 miles. The truck is in excellent condition for the mileage and starts, idles and runs great on both gasoline and CNG. The truck was previously owned by Southwest Gas in Phoenix, and I bought it last November.
About three weeks after buying the truck I was driving on the freeway in a heavy rain and started to notice an intermittent jerk, like a hard shift. I could tell something was wrong, so I stopped and switched over to gasoline and it ran perfectly.
In the days that followed, I determined that the truck ran without problems at speeds under about 40-45 mph (great for in town), but when lightly accelerating at speeds from about 50-65 mph it would buck/jerk. The transmission is not shifting, because I can feel the transmission shift normally and notice the change in rpms, and this buck is something different.
The buck/jerk happens only when driving on CNG.
To describe what I am calling a buck/jerk, imagine that you are towing someone with a chain and the chain comes tight after having a little slack in it. I also hear a noticeable "clunk" sound coming from the engine.
About three weeks later, and after experiencing probably 20 of these clunks, my #3 spark plug ejected. After a lengthy repair of the spark plug threads using the Time-Sert Ford Triton #5553 kit, I replaced all of the coil-on-plugs, spark plugs, seals and o-rings.
After firing it up, I did a vacuum test and the needle held steady at 18 in/Hg (elev 2,500 ft) and behaved correctly under sudden acceleration, etc. The vacuum did not hold after shutting the engine off (I don't know if it is supposed to).
I test drove the truck under all conditions and blasted up hills on the freeway at top speed with tons of power and no bucking or hesitation. I was elated! About three days later I felt my first buck.
Drained the coalescent filter again, and filled the housing with 90% isopropyl alcohol--drove about 50 miles and felt a buck.
Unsealed the tuning screws and returned them to the neutral position. The driver side screw was turned down at least three full turns fully sealed; that didn't seem right. After checking the high state O2 readings as specified in the manual, the neutral screw settings seemed to be giving good readings. This time I drove the truck for about 100 miles on the freeway before I felt a buck.
Today I finally received the correct coalescent filter element and I changed that out. When I drive the truck to Salt Lake this weekend, I fully expect to feel a buck and end up driving 80% of the way on gasoline.
My next step is to either sell it to some unsuspecting fool (I don't know if my conscience will allow that) or install a TechnoCarb system.
Sorry about the long post, but this has consumed the last 4 months of my life and I had to get it off my chest. Please help if you can.
Samuel
. Just kidding. I posted this to another thread that it also applied to but I think it fits better here:
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