Ive recently got a 98 Explorer with the 4.0 EFI 180k miles. Runs pretty good but Ive got some minor issues that Id like to get some opinions on.
First - codes 1151 & 1152 routinely pop up. It's been getting harder to start and runs rough for the first 30 seconds or so and then smooths out until it runs decent giving me 20 mpg with the air off. Occasionally it will idle rough and misfire at idle but that's a rare thing. I checked the fuel pressure today and it's 28 psi running at idle, about 35-38 with the vacuum line off the regulator. This is a little low per the manual which states 30-35/40-45. Also turning the key on, pressure slowly builds up and then drops down to near 0 before I start it, shutting down the pressure bleeds down to 0 in about 20 seconds.
I dont know when the fuel filter was changes last and that will be my next stop, but I also doubt that will solve the bleed down issue. It may or may not affect the pressure also. Would the concensious be more a fuel pump issue or a regulator issue? Ive got limited funds to throw at it and it is used daily. Would rather do the smartest thing if I can.
Assuming you just left the 'P' off the codes, they don't make a lot of sense. Per the factory service manual, P1151 means bank 2 indicates the fuel/air ratio is correcting rich for an overly lean condition. P1152 means bank 2 indicates the fuel/air ratio is correcting lean for an overly rich condition.
Do you have the ability to monitor the STFT and LTFT numbers?
The reader Ive got can only read the codes and reset the CEL and that's about it. There's been a couple other codes popping up occasionally but they're rare. 0171, 0174, and 0153. All O2 sensor related. I'm not so sure its an O2 sensor given thr rarity they appear and the quantity of sensors involved. Was hopeing it's be more fuel related since the pressure is on the lower side.