#5 miss fire. Bank 1 lean.

[nblehm]

New to me 2001 ford explorer limited 5.0. Previous owner just replaced plugs,wires. I got it cheap nowing it had a misfire. Now I cant find the source. I replaced #5 fuel injector which didnt pass the resistance test. I still have a miss fire though. You notice it worst in gear at idle highway speed you dont notice it. I have switched the coils side to side, tested the compression cranking and running. Running compression is 2 to maybe 5 pounds lower then the rest. So I did a leak down test, which checked out good 25%. I put a lab scope on #5 and another cylinders fuel injectors. Pattern looks good. I have switched the plugs around and wires. At the end of the wire the spark will jump a 1/2" gap easily. The plugs come out looking fouled and wetish (like no spark looking). When miss firing the O2 on bank 2 goes to about .7-.8 volts and the short term fuel trim dips to -19%. I am at a loss, and running out of ideas. Any help would be great.

thanks
Nate

 

[DR_APLET]

welcome to the forum.
well looks like you did you homework. the wet plug is interesting almost like the power never get to the plug. you know way more than i do but can you verify that the spark is making the jump at the electrodes of the plug and not through the boot somewhere, could the head have a crack causing the spark to be defused? otherwise you might be able to flash the computer perhaps it has corrupted timing. just some redneck ideas to bump ya to the top.

 

[nblehm]

bank 1 running really lean

2001 ford explorer 5.0

Back story, had bad valves on #5 so took both heads off to get rebuilt. Now bank 1 is running really lean. Short term fuel trim is 42% and its back firing etc. Bank 2 is completely normal. When I add propane it will drop bank1 to about 18% and bank 2% -18 to -25%. I have sprayed all around the intake looking for vacuum leaks. I thought the bank1 side intake gaskets could be leaking a little so I re did the intake no help. I am running out of ideas. Swapped both upstream o2's nothing. Any help would be much appreciated

 

[Turdle]

Time to check fuel injectors.

Edit, if this was all one thread I would have seen you already did.

 

[Turdle]

Threads merged

 

[Scout3]

Not familiar with the 5.0 but could your intake itself be cracked? You say you add propane and your Fuel Trim changes. Where are your adding propane. If you are putting propane around the edges and it changes then you know you still have a vacuum leak somewhere. Might be time to have a smoke test done.

Ed

 

[RomeovilleIL]

Bank one lean would make sense if an unfired cylinder showed rich on bank 2 since the computer would try to reduce fuel to compensate. Looking at what you have already done - swapping plugs, wires, coil, injector & compression tests -doesnt leave a lot left to test. Did you check the injector wiring for any fraying or shorts that might cause it to pulse a little slow or late? Have you noticed any coolant leaks?

As a simple shadetree fix you might try getting a hotter plug for just that cylinder to see if it can overcome the rich mixture. Once it burns completely the computer should level out the mixture on both sides based on O2 readings.