power surging
Junior User
Joined: Feb 2008
Posts: 80
Likes: 5
When I had this happen last fall it turned out to be a dirty idle air control. Cleaning it helped for a while but I had to replace it eventually. It was hanging up when it got a signal to up the idle and would not back off.
Senior User
Joined: Dec 2007
Posts: 128
Likes: 0
From: Florida
Sounds to me a Vacuum system leak
The Heater "passage" selections are vacuum operated on the 87 -91's, If it only happens when using your a/c and heater. Then I would check the vacuum system All Hoses and connecton points / the "Coffie Can"(Vacuum Resivor) / And the PCV. for leaks or possible leaks.
In fact the PCV may be going bad allowing a well hiden internal vacuum leak , comming through via the crank case.
Just because a PCV "rattles" when you shake it dose not mean it is not bad.
There is a light spring on top of a weight valve inside. If the spring is weaker then it is suppose to be , it will allow a premature weak vacuum to open it , instead of requiring a little stronger (RPM) vacuum .
The better quality ,more expensive ones are around $10 .
In fact the PCV may be going bad allowing a well hiden internal vacuum leak , comming through via the crank case.
Just because a PCV "rattles" when you shake it dose not mean it is not bad.
There is a light spring on top of a weight valve inside. If the spring is weaker then it is suppose to be , it will allow a premature weak vacuum to open it , instead of requiring a little stronger (RPM) vacuum .
The better quality ,more expensive ones are around $10 .
