changed front 02s, now throwing p1171

[jastutte]

1996 discovery stock engine.

previously, i was throwing p1179 codes every couple of days and watching my short term fuel trims indicated that i was running very rich. occasionally the ecm would drop back into open loop for several seconds then back to closed. so, after swapping in a good MAF and still getting the same codes and short term fuel trim readings i changed the front 02s.

now both bank 1 and 2 are running very lean, i'm throwing a p1171, and there is a flat spot in the acceleration all the way through the 2000's.

maybe crawling on top of the engine to unplug the stupidly placed 02 plugs i created a massive vacuum leak. checked with propane and didn't find anything.

if the 02s weren't seated properly could this cause the lean condition? again both banks are reading lean and the short term fuel trim values rise almost immediately and identically.

anyway, i'm at a loss, a little pissed, and not wanting to mess with changing the fucking 02 plugs again that some fucking british engineer brilliantly placed in possibly the least accessible spot on the entire the truck.

 

[RoverbyProxy]

Are you able to read coolant temp? Condition of the air filter? Did you swap back the maf? Does unplugging the maf change runability? Have you checked fuel pressure?

 

[jastutte]

coolant temp is good, 195-205, depending on the ambient.

air filter is good.

checked maf's.

i will check fuel pressure next, but truck always starts right up no matter how long it sits or doesn't sit.

 

[RoverbyProxy]

Generally, one that falls on its face is due to a bad maf or TPS. In your case it's odd because things reversed with new o2's. Leads me to believe that you have a wiring issue. You may have to ohm out your harness and inspect it real well. Clean connections and if you can, clean the terminals with a small file or pick.

 

[jastutte]

just thought i'd update the thread since i started it.


i double checked for intake and vacuum leaks and didn't find anything. checked again and heard a hissing noise from where the airbox connects to the maf. it looks like the plastic that holds the clips in place is pretty worn and is not allowing for a tight connection when clipped. so, for a temporary fix i used some form a gasket stuff and sealed up the connection.

truck is running fine now. no codes and no flat spots on acceleration. in fact, acceleration hasn't been this good for a while.

looks like i'll be needing a new airbox lid eventually, but for now since i have new 02 sensors and new rear brakes and rotors i'm going to hit the road and do some wheeling in southern mo.

thanks for all the suggestions and help.