Reader Question: My 1991 Mazda Protégé SOHC when started cold will rev very high RPMs until warm, about 5-7 min. It will not “kick” down.
I thought the Idle Speed Control Valve might be the problem. What are your thoughts?
Thank you for any help.
You might have an idle speed control motor issue, but first I would check a few things:
1. Is there a vacuum leak under the hood somewhere in a broken or missing plastic connector or is a rubber vacuum line off? Listen for a hissing noise when the engine is running.
2. Is the throttle body dirty? I would clean the throttle body as maintenance anyway just to rule that out.
3. Is there anything causing the throttle linkage to stick? Can you lube it?
4. Sometimes, you can clean the idle speed motor, just like the throttle body with a toothbrush and intake cleaner spray. If you can get access to it, try cleaning it.