01 F150 missing / shuddering on acceleration

[mohammond]

My 2001 F-150 bifuel seems like it's missing or intermittently fuel starved on acceleration running on CNG. Running on gasoline it works great, which seems to rule out any spark plug issues that would cause missing on a cylinder.

Compuvalve was replaced 3 weeks ago under warranty so I have tentatively ruled that out.

I have an appointment at the dealer on Wednesday but would sure like to fix it myself beforehand!

[CNG MOTORS]

Re: 01 F150 missing / shuddering on acceleration

Don't rule out the plugs or the coils, required much more spark from each to fire off the CNG and if you have a foiled coil could run on gas OK but do what's doing on CNG. Very common for these coils to fail. Or when the comp[uvalve was replaced they did not flash it with the proper codes to allow it to run on CNG properly

[Harpoon]

Re: 01 F150 missing / shuddering on acceleration

I second the plugs and coilpaks, also replace 3 o-rings per CNG injector cup. Fixed my rough idle under acceleration.

If you are a weekend mechanic like me I recommend doing the driver side one weekend and passenger side the second weekend. Each side can take 4+ hours the first time, and you do not need to feel rushed.

-Harp

[mohammond]

Re: 01 F150 missing / shuddering on acceleration

Thanks for the insights. Is there a manual out there I can buy to help with this? At best, I'm an "every other weekend" mechanic And the plugs look very tough to get to.

[mohammond]

Re: 01 F150 missing / shuddering on acceleration

I took the truck to Covert Ford here in Austin, TX. Covert services the Austin city fleet of CNG vehicles. They told me it was the coils - two of them, in the rearmost part of the engine. 10 hours of labor was the quote, and they suggested replacing all the coils while they are in there. Total bill, $2,400.

I hustled home and called Champion Ford, where I had the truck looked at in Utah when I bought it a while ago, and they told me 3 hours of labor. So next time I'm up in Utah I'll pay my friend Rob at Champion a visit. Just hope I don't need to go back to Covert.

[darress]

Re: 01 F150 missing / shuddering on acceleration

Although $2400 is crazy, don't think that the dealer here in Utah will do it for much less. The repair time is the same taken from the standard labor rate calculations. I had a quote for spark plugs alone at the same dealer for about $1400. Of course they would have added in coils and injector o-rings once in there, if I would have let them even start. I suggest sourcing all the parts yourself online, sno-motion for a viton o-ring set, and do it yourself. Sno-motion in SLC does it for around $1200 total I think. Give them a call. Also, search in this section, several of us have done it and posted info.