Idle problem C4 1989

[Blue89]

Looked for a thread that addressed this but to no avail, so, when I start my car it idles at about 600 RPM and as I'm driving, the darn thing wants to race to about 1700 RPM and won't come back down until I shut it off and then at restart it idles about 600 RPM again. Also, when it does race, the temp goes to about 240!!! :confused :confused :confused

 

[BADDUCK]

Could be the TPS.

 

[Blue89]

Appreciate the response, I'll check it out.

 

[MBDiagMan]

Appreciate the response, I'll check it out.

If this is a high mileage car, the problem might very well be a worn throttle shaft allowing the throttle plates to drag on the bore.

 

[vetteoz]

If this is a high mileage car, the problem might very well be a worn throttle shaft allowing the throttle plates to drag on the bore.

Will idle reset if you give throttle a quick sharp stab?
If so TB is worn as stated above
Slow closing on a worn TB allows the butterflies to pull to one side, hanging up on the bore instead of seating closed properly

 

[Blue89]

Not really high mileage for the year, closing in on 100k. Idle doesn't come down after a "stab", only when shut off and restarted.

 

[boomdriver]

Looked for a thread that addressed this but to no avail, so, when I start my car it idles at about 600 RPM and as I'm driving, the darn thing wants to race to about 1700 RPM and won't come back down until I shut it off and then at restart it idles about 600 RPM again. Also, when it does race, the temp goes to about 240!!! :confused :confused :confused

All the symptoms of air leaks...
perhaps the IAC is not closing and allowing extra air.

 

[Blue89]

I'll check that out also......

 

[Blue89]

Anyone have a problem getting the bottom screw out of the TPS when changing it?? Does the TB have to be removed or can it be changed with it on??

 

[boomdriver]

Anyone have a problem getting the bottom screw out of the TPS when changing it?? Does the TB have to be removed or can it be changed with it on??

It just requires the right tool to get to that lower bolt...Lots of stuff in the way. A long bit does the trick. hex and torx are available.

have you tested the TPS and determined that it is bad? An inexpensive multimeter is all it takes. The new one will have to be "set" or it won;t perform any better.