I need help from you engine guru's.
This may not be the right thread but you seem to discussing things that are close to the problem I have.
I have a 99 XL with a 4.6 that runs on propane or gas. When I'm running propane my truck runs fine except for a very minor intermittant rough idle problem. I've fixed that for the most part by replacing my iac valve, cleaning the maf filaments, setting my tps to .991 and getting the mixture adjusted. At some point i will be replacing my upper o2 sensors as I have almost 100k on the engine and feel I should replace them due to normal fatigue.
Here's the problem finally!! When i run on gas, it seems I have a miss that is driving me nuts! I'll be driving down the road at steady throttle and it feels like I'm only running on 7 cylinders. I step on the gas to speed up and it'll do the 7 cyl. thing for a bit then all of a sudden pick right up and run on all 8. If I go WOT, it's fine. No codes! As it runs well on propane I can only conclude that the problem is in the fuel delivery somewhere. My take on the matter is as follows: Water in the gas. Bad fuel filter. Bad o2 sensor. Bad injector.
I've only had this truck since Sept. and the previous owner had had a missfire cyl.1 code a couple of times but I haven't seen that myself yet. When i got the propane mixture set up the mech said I had a lean right side code that he attributed to the propane mixture thing.
Any ideas? I'm slowly going insane with this problem.
Please help before I'm hauled off to the funny farm.