1999 Ford Taurus High RPM during comute driving

SFAKINS

MEMBER
1999 FORD TAURUS
6 CYL
FWD
AUTOMATIC
124,000 MILES

During commute driving when the engine get hotter then normal, the RPM becomes excessively high. This will cause hard down shifting in the lower gears when slowing down. In addition, when putting the transmission in park, the engine will sometimes increases to between 2000 and 3000 RMP and will stay there until I stop the engine. I get no codes; however, I went ahead and replaced the IAC valve and TPS. Neither helped the situation. Another symptom is if I am driving on the interstate at 55 MPH with the engine at normal engine temperate, let off the gas and put the car in neutral, the engine will increase between 500 – 800 RPM and stay there for about 10-15 seconds.

Tuesday, July 27th, 2010 AT 10:09 AM

3 Replies

KHLOW2008

MECHANIC
41,814 POSTS

Hi sfakins,

Thank you for the donation.

Do you have overheating or coolant losses issues?

From the symptom description, seems the PCM is giving the idling control system the wrong signal.

The best way to go about would be to plug in diagnostic equipments and go for a test drive. From there you can check the working conditions of the various components.

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Tuesday, July 27th, 2010 AT 12:22 PM

SFAKINS

MEMBER
2 POSTS

Thank you for your response. However, as a DIY the only test equipment I have is my OBD II, CAN & ABS Can Tool by Actron (model CP9580). Like I said, I've all ready replace the TPS, MAF and IAC valve. I am planning on replacing all for O2 sensors because they have over 125,000 miles on them. I guess my question to you was what else could be causing this problem. Faulty EGR solenoid/valve. Faulty CKP? I all ready knew I could take it to a shop and pay $95 per hr to have someone drive around in my car for a couple hours with test equipment. Any additional insight to this problem would be of great help.

Also, if this is a PCM problem, does a new PCM have to be reprogrammed by the dealership.

Thanks,
Steve

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Thursday, August 12th, 2010 AT 2:10 PM

KHLOW2008

MECHANIC
41,814 POSTS

If the PCM is replaced, it has to be programmed with Ford Service Function Card and NGS Flash Cable so you would need to send it to the dealer.

When idling is irregular, the most common fault would be the IAC but during driving, the MAF would be the more likely cause. Was the MAF replaced new or used and is problem exactly the same as before replacement or are there any changes?

Other things to look for would be vacmun leakages that occurs only at higher engine speeds. Maybe some solenoid valves that are activated are faulty resulting in vacumn leakages.

Should not be the CKP but possible to be the EGR vacumn side.

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Friday, August 13th, 2010 AT 6:49 AM