Well here is the problem, on my 91 F150 302 4x4, four cylinders are not firing. I get a very weak spark if any on cylinders. The firing order is 15426378, cylinders 2637 are the ones that are not firing.

I know they are getting fuel, wet plugs, gas in oil (had to change oil yesterday). I measured voltage in the TFI harness and it is getting voltage, and if the TFI isn't working it wouldn't be getting fuel. I am thinking that it is the PIP sensor.

Any ideas or suggestions on what to check?

Thanks

 

If the coil checks OK, replace the TFI module. A faulty module will in no way impede the fuel injectors. They fail all the time. The local parts store should be able to test it for you.

 

I would also check the wire harness to the 4 injectors on those cylinders. I beleive those 4 injectors are all fired together. I would look to see if the harness is shorted to ground. That would make the injectors fire all the time, causing fouled plugs and enough gas to wash down into the pan.
I know it is a bank fired EFI, but I'm not sure which injectors are in which bank. I will do a little research and try to find out.

If the PIP is bad, you will get mis-fires and back fires, or a complete no-run situation. I've never seen one that only caused certain cylinders not to fire. But, then again, I could be completly wrong.

Roger Lane