1999 Ford Explorer RPM issues while driving

GRABULA

MEMBER
1999 FORD EXPLORER
6 CYL
4WD
AUTOMATIC
149,000 MILES

I've taken my vehicle to a mechanic 3 seperate times and he has no idea what the issue is. He says he can't duplicate it but for me it happens just about everytime I drive it. Here is the breakdown I gave him:

- When maintaining speeds of 35mph and 55mph, RPM's drop down from 2000-2500 to below 2000 and I can't get any pickup or gain any speed. I can take my foot off the gas and then press it again and sometimes that fixes the issue.

- When this happens I can maintain speed but cannot accelerate.

- Occasionally while idling the RPM's drop down repeatedly. It idles at around 1100-1200 normally, but drops down to about 500-800 repeatedly about every few seconds.

- Occasionally while driving at high speeds 55+ there is a loud "clunk". This is typically when roads are in a bad condition. We have confirmed 4 wheel drive is not working and I suspect this may be related.

I bought the truck in August and since then it's gradually got worse. It seems to occur more frequently when the engine has warmed up a little.

Thanks for you help in advance.

Jason

5 Replies

JACOBANDNICKOLAS

MECHANIC
108,300 POSTS

THe clunk could be many thngs, shocks, ball joints, tracking arm bushings. They will need checked to determine which is bad.

As far as the engine, has the check engine light ever come on? It sounds like a bad Throttle Position Sensor (TPS). Also, has anyone checked the catylatic converter to make sure it isn't plugging?

Let me know.

Joe

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Thursday, January 14th, 2010 AT 9:02 PM

GRABULA

MEMBER
3 POSTS

Joe,

The check engine light is on and has been since I've owned the truck. They turn it off when they look at it but it comes back on within 24 hours of driving it away from the shop.

It's becoming frustrating. I took it in for the third time last week and monday the mechanic said he couldn't reproduce the power issues. Everytime I drive it for mroe than 10 minutes I can produce the issue and after noticing my gas guage had barely moved I suspect the guys just not really trying. When I asked him if he had any guess as to what might possibly be causing the issue he said he had no idea.

I found a site indicating that a bad Mass airflow Sensor might cause the kinds of issues I'm having. I think what I need to do is just bring it to another shop and have them look at specific issues.

I'll put Throttle Position Sensor on the list of things to have checked.

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Friday, January 15th, 2010 AT 6:57 AM

JACOBANDNICKOLAS

MECHANIC
108,300 POSTS

If the check engine light has been on, what code is it identifying? From the code, the mechanic should know what is causing the problem or at least an idea where it is coming from.

Try this. Take the vehicle to a nationally recognized parts store and have them scan the computer. Most do it for free, so there is no money out of pocket. When they check it, they will tell you what they are finding. Get the trouble code number so I have a better understanding of where the problem is coming from.

Let me know if you do it and what you find.

Joe

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Friday, January 15th, 2010 AT 11:29 AM

GRABULA

MEMBER
3 POSTS

Joe,

The mechanics run the scan on the computer. The first time I can't recall what the code was but it led him to clean a sensor of some sort. This didn't help.

This time around he said it was indicating a problem with a different sensor (again I can't recall which) but he said that shouldn't be what's causing the problems I'm describing.

That's the tough part. I can't tell if the mechanic I'm bringing it too is incompetent or uninterested in fixing my truck or what. I'm a computer tech myself and understand the complexities of tracking down a "general" issue like this but monday when he indicated he didn't even have a guess as to what might be causing the problem, I just felt like he wasn't really looking into it hard enough.

My vehicle is under warranty for another 5000 miles and if it's something that's covered I'd really like to get that figured out before I'm either stranded on the side of the road on a cold night or can get it fixd with no hit to my wallet.

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Friday, January 15th, 2010 AT 11:55 AM

JACOBANDNICKOLAS

MECHANIC
108,300 POSTS

Try what I said with the parts store. Let me know what you find from them.

As far as the warranty, I agree with you. I strongly recommend that you make them aware of what is going on and that the problem exist and no one can find it. That way, they are aware of it happening while it is still under warranty and they may have a recommendation of one of their shops in the area that can find the problem.

Let me know.

Joe