'88 Engine Idles at 5500 RPM
 

My 1988 stock convertible, started running at 5500 RPM constantly. I was driving home from a funeral, car had been behaving normal, pulled out from a stop and when I went to shift to second gear the engine raced to 5500 rpm. I got it home and continues to do this. The car is completely stock, had a new Mazda factory motor installed about 8,000 miles ago. Current mileage is 162,000. Car does not get driven very mush, less than 1,500 miles per year. I have checked all throttle linkage, all seems normal. No obvious vacuum leaks. The first set of butterflies are open and forcing them closed does not reduce the RPM. Manually moving the throttle, via the cable, has no effect except at the very top end which raises the RPM even higher. Thanks for any insight, nobdy in this small town even knows what a rotary is!

The throttle body should snap shut even if the cable is not attached.
Take the cable off and see if the TB is hung wide open.
If it is then there is your problem,.

Accelerator cable removed throttle body in idle position, accelerator cable reattached, throttle body in idle position. You can manually open the throttle body and when you release it, it springs shut or idle position.

I had a TB stick on me and pretty well had to take it apart and lube it up.
Try 6K RPM coming into a trailer park over speed bumps..it is interesting.

The cable itself is fairly short so you can spray it if you remove the small rubber cover near the Adjust/TB area and it will run down to the pedal.
The Cable only attaches by a plastic grommet on the cable so it is easy to remove if you have to.(besides the pain in the ass clips on the firewall if you go to replace the cable all together.)
Now if you feel it is the Throttle body and you don't want to screw with it,you can always place an AD in the SEC Gen Parts Section and post a WTB to acquire one.
The guys here are easy to get along with and I am sure someone would have a good replacement for you at a decent price.

My car a few months back did this same thing, somehow the cable came out've the "guide" on the TB and was hanging it open somewhat, it LOOKED like it was closing completely, but it really wasn't

Thanks for all the suggestions, the cable seems to function as expected. Looking at the butterflies in the "Dynamic Chamber" they are completely closed yet the engine races to 5500 RPM. Is there an electric control or vacuum that could make it race like this?

How did you know the TB was stuck? Don't mean to sound ignorant, but the TB seems to open and shut as expected. Is there something I should specifically look at? Thanks for all the time in responding to me.

Does the car have cruise control and if so check the cable for that as that can also cause the car to idle at a much higher speed than normal. And an AFM which is stuck open could possibly cause your problem. Also, if you look inside the throttle body with the intake duct off and engine off you are seeing the throttle plate position in a position which is likely not the position it assumes w/the car running. And try pressing upwards on the front throttle linkage if the engine is idling at an inordinate speed to see if this lowers the rpm or not. Last but least, check to see if the plunger on the TPS is stuck in the extended position.

Folks, I found the culprit! After so many indications that it was the throttle cable, I started looking again. AS you know it is in a difficult location. With the help of an inspection mirror and a small flashlight, I noticed the "cruise control" cable had jumped its track. Once I positioned it in the guide, the engine is back to some what normal. THANK YOU for your patience and sound advice.

Please do not Close your thread in the future.
All info needs to be available to others and if they can add info they readily can.
Thread is re-opened.

My 88 GXL can jump the cruise control cable off its track on my command! If I press the on/off button very quickly twice while driving the cable comes loose and jams the throttle linkage. It has done this twice, can I adjust the slack out of the cable like removing the slack from the throttle cable? For now I just make sure I press firmly once.

Gary

yes you can, just slip off the E clip and pull the cable and adjust the seating nut.