Rough idleing

[JVANBUREN]

I am having a problem when you are rolling to a stop at about 30mph my car wants to idle back and forth from 500rpm to 1100 and it will keep doing it, and just recently on my way back from a trip I had the cruise set at 75 and it seemed like it was free reving from 2500rpm to 3000 and it would so this every minute or so. My car also seems to be running preety rich. fuel pressure is good.

1997 Taurus SHO

 

[wuzzzer]

I'm going to assume that when you were driving on the highway you had the A/C or the fan on, correct? This is normal operation that happens when the A/C clutch engages/disengages. It causes the RPMs to fluctuate a little bit.

For the other thing mentioned, I guess I never looked at my tachometer much as I was slowing down, but it could very well be the car just downshifting into a lower gear?

 

[Mr. SHO]

Sure sounds like the TPS to me. Check the TPS wiring. Sometimes cleaning it up helps. Other times, the TPS itself, or the related wiring needs to be replaced. The TPS is uber-cheap and available everywhere (standard Ford part).

It could also be the IAC, but that's less likely and more expensive. Swap the TPS first.

 

[JVANBUREN]

THANKS!!!!!!!!!!!! it was the tps. I was stumped because it was not throwing any codes.

 

[Chud97]

What is the TPS? I have the same problem with my 97 SHO

 

[SHOMEX]

TPS = Throttle Position Sensor. You can clean the connection to the TPS and see if that fixes the problem or replace the TPS.

 

[Chud97]

Also what is IAC = Idle Air Control?

 

[SHOMEX]

Also what is IAC = Idle Air Control?
Yes that's what it is and it's located on top of the throttle body.