2000 4.0 SOHC misfire

[JSargeSter]

Hey yall

I've been chasing a misfire that doesn't stay consistent to one cylinder. It seems however it staying frequent to the passenger side bank.. p0301, p0303. I've read that cross connected O2's can cause a weird rich/lean situation. I try to process through my mind how you could cross connect them, granted i haven't particularly paid attention.

Injectors have been professionally cleaned and flow tested, upper and lower intake gaskets, new motorcraft coil, plugs and wires. Ive pulled the plugs, and it does seem lean in my opinion. 64 PSI of fuel rail pressure at idle, and stays consistent throughout engine speed increases. Compression is 150-160 cold on all six. 162k miles.. Checked for vacuum leaks only using some carb cleaner around all of my work up top.

Any ideas on where to go next is much appreciated.

Sarge

 

[JSargeSter]

Forgot to mention, also cleaned IAC, MAF and TB.

 

[J_C]

I'd look at long term fuel trims on a scan tool capable of live data. I assume all the things you listed, were done after it started misfiring, so no chance that any of them were done poorly and that caused it? If only cyl 1 & 3, any chance the plug wires got mixed up? I'd also wonder of the MAF even after cleaned, is reading low, if no vac leaks can be found.

 

[JSargeSter]

I'd look at long term fuel trims on a scan tool capable of live data. I assume all the things you listed, were done after it started misfiring, so no chance that any of them were done poorly and that caused it? If only cyl 1 & 3, any chance the plug wires got mixed up? I'd also wonder of the MAF even after cleaned, is reading low, if no vac leaks can be found.

I have a scanner capable of live readouts and both upstream o2’s both cold and once up to temp were all over the place regardless of throttle consistency. 0.080-0.800v. After a hard run to the top (me giving about as much of a damn as this old turd is worth) .. it cleared up. Its ran near perfect with no trace or smell of unburnt fuel like before. No CE light, and fuelsys_01 is reporting closed loop.

Ill report back..