Idle Issues and Codes

[Drg racr]

For a while now, my '01 Explorer 4.0L OHC has had idle issues when it's real cold outside. First thing upon startup, it would idle rough and die. After about 30 seconds, it would smooth out. The PCM was throwing codes indicating a lean condition in both banks. Also, when driving, it would buck like it's trying to misfire at around 2000rpm. Hitting the throttle would make it stop, but then it would return when back at 2000rpm.
Fast forward to this now (very warm). Now, it idles okay, but still sometimes will stumble at cruising speed. I cleared out the codes a while back to see if they return, and now the only codes is PO1471, and it'll kick it out as soon as the truck starts. Clear it, and it immediately kicks the code again. But no lean conditions codes. I sprayed carb cleaner all over the motor at the intake, vacuum lines and other spots, no difference in idle.
Question. Could it be my intake seals? MAF sensor? IAC valve? I have cleaned the sensors once.

 

[koda2000]

Do you mean P0171 and not P01471 (I assume so). This is still a lean condition, just on one bank (bank 1 - passenger side of engine).

If you have the Job 1 engine (Oil filler on driver's side, 2 piece intake manifold) it is most likely that your upper and/or lower intake O-rings are leaking when the engine is cold. My '97 SOHC does this all winter, but is fine once the engine warms up and during the summer months. I just haven't gotten around to fixing it yet.

The Job 2 engine (late '01 on, oil filler on the passenger side) is less likely to suffer from this problem, as the intake manifold is a one piece design and the O-rings are much fatter.

BTW, Spraying starting fluid all over the engine is not a very good way to diagnosis an intake manifold leak on these engines. A smoke test works much better.

 

[J_C]

That's an odd code for this symptom, are you sure it isn't P0147 which is an O2 (bank 1 sensor 3) sensor code? Edit: I think koda's reinterpretation of the code makes more sense than mine.

Have the plugs and wires been replaced in the last few tens of thousands of miles? Battery voltage is good at startup?

 

[swshawaii]

Good info koda. Job 1 oil fill is on the drivers side. Or does that only apply to 2001 ST's?

• If you have the Job 1 engine (Oil filler on passenger side)

 

[koda2000]

Good info koda. Job 1 oil fill is on the drivers side. Or does that only apply to 2001 ST's?

Actually not so good info - I had it backwards, Job 2 has oil filler on passenger side. Job 1 has it on the driver's side. I will edit my post.

 

[Drg racr]

I just checked it again today after clearing it, it's showing P1451 and P0171. Battery voltage good, plugs and wires replaced last year, always maintained. Passenger side filter, 166K miles. It does leak a little oil, but not bad.

 

[koda2000]

I just checked it again today after clearing it, it's showing P1451 and P0171. Battery voltage good, plugs and wires replaced last year, always maintained. Passenger side filter, 166K miles. It does leak a little oil, but not bad.

P0171 is because you have a vacuum leak apparently originating from the evaporation canister purge valve (P1451). This is located under your vehicle, above the spare tire. The valve is probably stuck open, or perhaps there is a leak in the evap canister. The canister mounting bracket is notorious for rotting away.