Engine starts at 400 RPM after long drive in hot weather

[begleysm]

Hi all,

I have a 1998 Ford Explorer Sport 4WD. It has 150,000 miles. Sometimes, in the high heat of the summer (over 100*F) after driving for a while I'll turn off the engine (say, go into a store for 10 mins). When I come back out and start the vehicle it idles around 400 RPM instead of the usual 1200 or so. The fix is the disconnect the battery for a couple minutes, reconnect. Occasionally I have to do this twice. After that, the engine starts up just fine and I'm on my merry way. Once is starts it never dies (at lights, etc).

Any ideas what is going on?

Thanks,
Sean

 

[exploration1997]

I have the same problem with mine, except in cold weather. Does revving the engine a few times get it back up to 1000-1200 RPM's? I usually just do that and it works. Although this one time, I went to start mine up, and it idled around 200 RPM for a few secs, and died out. I restarted it instantly, and everything started up just fine.

 

[begleysm]

I can rev up. But it will drop back down to the low idle. It won't stay up where it should be.

Sean

 

[rwing21]

How is your fuel pressure?

 

[colintrax]

Is it stumbling at 400? If the engine is not stumbling, and it'll rev back up then I say leave it alone.

 

[begleysm]

rwing21: I don't know how the fuel pressure is (or how to check it) but the car runs fine (and idles correctly at 1200 and starts up on the 1st try) 99% of the time.

colintrax: The engine will die in the 400RPM instance. It also will not magically pop back up to 1200RPM during that event. I can manually rev to whatever I want, but it will drop back down to a 400 idle.

 

[colintrax]

So it's stalling? And I know it's not "magically" reving back up. When I said "rev" that means you have to touch the gas pedal.... unless your explorer can drive itself

 

[begleysm]

In that instance it will stall. It will rev up if I press the gas pedal.

 

[colintrax]

Ok. You might wanna check the IAC valve.
The MAF can cause all kinds of weird problems, so it wouldn't hurt to clean it.
BTW don't bother cleaning the IAC valve, works temporarily before the valve completely craps out

 

[begleysm]

Thanks colintrax.

 

[colintrax]

No problem. Also is 1200 normal for you? I think it should be idling around 800, 1200 is my cold idle.

 

[begleysm]

I'll double check it. I'm going from memory.

 

[boominXplorer]

The problem when hot makes me think intake gaskets. The lower single o-ring ones that go to the head to lower intake manifold usually are toast by 150k assuming you have the 4.0 sohc.

 

[begleysm]

I have the 4.0 EFI engine.

 

[colintrax]

Intake gasket leaks cause a problem throughout the rpms though. Not just idle

 

[colintrax]

The "efi" is the OHV

 

[boominXplorer]

Intake gasket leaks cause a problem throughout the rpms though. Not just idle

The 98+ ohv also have rubber o-rings on the intake manifold. A light vacuum leak when hot will not be detected at all through RPMs, just at LOW idle. The only drivability issues it might cause is a CEL or a lean code.

 

[colintrax]

Huh, ok. Well I learned something today