Neighbors .... this problem has me pulling my hair out. 2000 F150 Harley Davidson 5.4L, 48,000 miles. The whole thing started when I changed the exhaust to have true duals into a single muffler. That eliminated the bottleneck where the pipes joined after the cats. The cats were left unchanged. I knew that a lean condition would be produced so I planned to go up one size on injectors.
After I installed 21# injectors, the center 2 cylinders on driver's side weren't firing. I thought that I had done something wrong, so I checked to see that all was connected properly and replaced injectors again. No change.
All spark plugs removed to see if any were wet, black, too white, whatever. All look normal except one had a small dark spot on the anode. I cleaned all with brake cleaner and hard bristle brush, rinsed and blew dry with compressed air. Spark plugs kept in order and reinstalled in same cylinder they came out of and ... no improvement.
Tested compression because no fire was adjacent. It came out 202, 184,186, 195.
COPs looked edgy so changed all 8 COPs. No improvement.
Still suspicious that I had messed up, I changed both injector and COPs connectors. One of the cylinders is firing, but I don't know which yet.
Today, I'll pull plugs to see what condition they are.
This morning checked codes for the umpteenth time and got a P1151 Lack of HO2521 sensor. I guess that's the O2 sensor that should have coded when exhaust was modified.
Y'all probably have more experience than I at this stuff, so maybe someone can poke a hole in my troubleshooting. Maybe someone can tell me where to look for spark and injector triggers.
Crank and cam sensors are used to fire and time the ignition/injectors. Then the advance, retard and pulse widths vary due to temp, airflow, tps position,etc.
Honestly, you need to put the stock 19lb injectors back in. Opening up the exhaust behind the converters, does not warrant larger injectors. They will not calibrate correctly since the PCM is trying to fire 19lb injectors.
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Too wierd
