racing idle....anyone ever had this???

[naps]

i have a 1987 Mercury Grand Marquis 5.0 85,000 mi. No major problems

until now it seems. The idle started to RACE. I could go 30 miles an hour without touching the gas. We replaced the idle control valve, but that didn't do anything to remedy the problem.

Before this happened we gave the car an oil change which included changing the air and oil filter.

I do not believe that it is an air filter problem. Could it be a fuel pump problem or some problem with a sensor?

I am not very knowledgable about cars, so any CLEAR and STRAIGHTFORWARD advice is very much appreciated!!

[naps]

someone told me it could be the throttle position sensor (computer controlled)

Does this sound familiar to ANYONE?

[6502dude]

Check for a sticking relay.

I changes TPS on spec and then paid dealer "technicians" over $200 before I found the the problem myself and changed the $10 part.

Relays are located on passenger side engine compartment over wheel.

[Merc_Cruiser88]

On my 86 Merc, it idles very high sometimes only when ts cold though.

[6502dude]

Originally Posted by Merc_Cruiser88

On my 86 Merc, it idles very high sometimes only when ts cold though.

All cars will idle higher when cold (below approx 50F).

Many years ago, folks had to use manual chokes when they needed to start their cars in cold weather.

Higher revs below operating temperature should not be confused with Naps problem.

[0ºKelvin]

Some older Merc's (late 80's), were equipped with an idle speed actuator. It was essentially a computer controlled servo that had a plunger that would push the throttle open to increase the idle, like when you put the car in gear or turned on the A/C. You should be able to see it adjacent to the throttle lever, probably right near the throttle cable.

The actuator has a metal tip which makes an electrical contact with the throttle lever. When this contact point becomes corroded, the actuator, while physically contacting the lever, is not electrically contacting it, thus the computer commands the actuator to extend itself until it does. Since it never makes an electrical contact, the actuator extends to its limit and pushes the idle up to a very high RPM, enough to maintain about 30-40 mph depending on the car model.

If your car has one of these, clean the tip of the actuator and the throttle lever with some Scotch-Brite, then spray it with WD-40 or smear some Vaseline on it to keep it from corroding again.

[GrandmasCar]

I have encountered this twice on my '87 GM. Once was because of a sticky throttle linkage. Have someone press/depress the gas pedal while you spray the linkage with WD-40. The other time was because the throttle position sensor went bad. You can't fix/have to replace. Hope this helps.

[carmel 9]

I had this problem took car to dealer and had the Idle air control valve replaced part was 94.15 and labor was 131.43 and that cleared up the rough Idle. Hope this helps