99 Explorer dies when hot...

[NCShooter]

I've got a 99 explorer 4x4 w/ the 4.0L motor. Twice now the truck has ended up dying at the most congested intersection of my town (always fun LOL). It will drive fine for quite some time then decide (usually on the hot days) to act up. This truck lead a hard life, luckily I got it for free so spending a bit of coin to fix isn't an issue

Symtoms are as follows:
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- When starting cold, the idle is very low, rough, <700rpm. Any throttle will not change behavior. The idle will usualy fix itself within 10 seconds and shoot to around 1500, slowly backing down to the usua 750ish rpm. From that point on it is fine.

- The truck drives fine, albeit with a little less power than one would expect.


- After driving for a while, it will start hesistating when moving from a dead stop. It usually recovers with a bit of throttle input, hesitation doesn't last long athough sometimes it seems throttle makes zero difference in actually applying power...

- If the vehicle sits for a while after stopping, it will crank up and run very rough, no power. Any throttle is essentially ignored - I had it WOT and it was stuck at 500rpm. Within 30 seconds it will stall out and *not* start again unless it sits for an hour or so. NO CEL codes thrown (this time at least)...



So it seems to be heat related and only really repros (complete failure) after driving for a while and stopping. I will say I noticed what sounded like a howl from the airbox area... I had it running then just unboling the airbox cleaner upper housing caused it to die It is loud and usually my early warning that the issue of imminent failure was going to occur. Thus I was originally thinking some form of massive vacuum leak only occuring when hot(??). My other thought was fuel pump since I have had simmilar behavior from other cars.

Maint.
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I haven't devoted much time to the truck yet, but here is what has been done:

Drain and refill tank -- still had old fuel in it
Replace fuel filter (it was clogged)
Seafoamed


I was throwing a lean condition code, but that went away after the fuel filter change.

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Thoughts?

 

[Millertime1987]

Have you checked the radiator? May need to fill it with new antifreeze if its hot. Also do you see the temp gauge go very high?

 

[BIGTREAD]

No answers, but I'll be watching this thread. I just did a 98/2000 ohv swap and am having very similar problems. I assume it has something to do with the swap, but these idle and stall symptoms sound the same. I did a fuel pressure check and found constant pressure, so ruled that out.

 

[NCShooter]

Have you checked the radiator? May need to fill it with new antifreeze if its hot. Also do you see the temp gauge go very high?

Gague never moves beyond half mark, seems to function just fine. Radiator is full of new coolant also, no indication of an overheat condition.

I did just clean the IAC motor which seemed to stabalize the idle a tad. I proved that it worked by cleaning, replacing then unplugging once the car was at idle. The idle dropped quite a bit, almost to stall. Plug back in, back to normal.... although the "owl" noise (hard to describe) was present today much faster. From what I read the IAC can cause that.

Reving the motor at a standstill you can feel a hesitation in the range, a bit of a stumble. No codes even after beating on it for a while (in driveway).

 

[russosborne]

How old was the old fuel? Did you do anything to clean out the tank itself? You could be picking up some left over junk in the tank, and it could be clogging the filter some. Or even clogging the pump itself.
This probably isn't the case, but just throwing it out for consideration.
Russ