1999 Ford Explorer 99 Explorer Stalling

Tiny
CMILLER.05
  • MEMBER
  • 1999 FORD EXPLORER
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 150,000 MILES
I have a problem where while driving at a low speed with very little to no throttle, slowing down, or trying to stop, my RPMs will waver and drop. Sometimes the engine will stall. I will have to restart the engine while driving or stopped. Sometimes I can tap the brakes or gas and the RPMs will go back to normal. I have a code on the dash. I have pulled it. It talks about something running lean. This points to Mass Airflow Sensor. I have removed, cleaned, and reset the system twice now. The problem was temporarily fixed the first time. The problem got worse (aka happening on a regular basis now). I was wondering if there is a way to bypass or fix this problem, or if anyone knows what exactly is causing it. I might also have a bad catalytic converter. Could that be causing my problems. I greatly appreciate any assistance.

Thank you ahead of time!
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Wednesday, June 30th, 2010 AT 1:56 PM

8 Replies

Tiny
JACOBANDNICKOLAS
  • EXPERT
A lean mixture can also identify a vacuum leak. Have you checked for that?
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Wednesday, June 30th, 2010 AT 11:50 PM
Tiny
CMILLER.05
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I have not checked for a vacuum leak. I'm not necessarily sure how to go about that. Could that explain how my MAF sensor keeps getting dirty and clogged? What's the best course of action for checking for vacuum leaks?

Thanks
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Thursday, July 1st, 2010 AT 2:34 AM
Tiny
JACOBANDNICKOLAS
  • EXPERT
Is the MAF getting clogged with dirt? If so, is the air filter good? Also, there are several vacuum hoses that are on and around the engine. I would recommend checking for any broken, disconnected, or dry rotted ones.

As far as the MAF getting dirty, do you live in an area where there is a lot of dust and dirt?
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Thursday, July 1st, 2010 AT 1:09 PM
Tiny
CMILLER.05
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I don't live in a dusty or dirty area. I will take a look to see if I can find any dry-rotted or weathered hoses. I'll also check for any disconnected or broken hoses. The MAF sensor seems to be getting clogged with grimy dirt. The air filter I good. I'm not sure what is causing the ridiculous build up.
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Thursday, July 1st, 2010 AT 10:03 PM
Tiny
JACOBANDNICKOLAS
  • EXPERT
Have you ever noticed any oily substances on the air filter or in the intake where the MAF is located? Have you ever replaced the EGR valve? I'm starting to think the engine may have blow-by and allowing oily air from the engine is making it way through the PCV and into the maf.

Let me know. Here is a little check. With the engine running, open the oil fill cap and see if there is a lot of pressure coming out of it.

Let me know what you find.
Joe
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Thursday, July 1st, 2010 AT 10:33 PM
Tiny
CMILLER.05
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Yes.I have noticed that the dirt is usually grimy or oily. I wasn't sure what was causing that. If I do have a blow-by problem, how do I fix it?

I have not replaced the EGR valve because I have never pulled a code referring to that problem. I had another vehicle with that problem before.

I will try that oil pressure test you were referring to. If there is a lot of pressure coming out, what does that tell me?

I am definitely not a mechanic. I have worked on cars a little bit in the past, but it has mostly just been maintenance work.

I appreciate your help, Joe.

-Chad
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Friday, July 2nd, 2010 AT 10:01 AM
Tiny
JACOBANDNICKOLAS
  • EXPERT
Chad, The EGR valve won't cause a code. It should be part of a tune up. As far as checking if there is a lot of pressure coming from the oil cap when opened, that will tell me if there is excessive blow-by. What causes that is worn piston rings. When the piston builds compression, bad rings allow compression to escape into the crank case. If that is the problem (which would be odd at this mileage), the only thing you can do is replace the rings.

Let me know what you find.
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Friday, July 2nd, 2010 AT 12:58 PM
Tiny
CMILLER.05
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Sorry for the delay on my response. I have been extremely busy for the past couple of weeks. I did get a chance to check the cap for pressure build up. I didn't find anything out of the ordinary. When I pulled the cap off, while the engine was running, I put my hand over the fill hole and didn't really feel any pressure.

I don't know if this helps or not, but when I have the a/c running, the problem occurs much more seldom. The a/c running seems to help. I'm not sure how that works, but it's an observation I made.

Well, I hope you might have some more insight into this problem. I greatly appreciate your assistance.

-Chad
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Friday, July 16th, 2010 AT 8:18 PM

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