I have a 93FD. Its running fine. But this morning when the car warmed up and I was at stop light in neutral. The idle jumped up from about 800 to 2000 than back down again. It repeated this over and over than stuck on 2000 for a few seconds than back down. A/C wasn't on and either were the lights. When I turned the A/C on it just jumped up a little higher to around 3000. Could it be the ISC solenoid? Any thoughts?

 

Could be any thing, but just to guess- disconnect and block the aws as if it may be comming on incorrectly, and you do not need it any way. Pull the ISC off and clean it ,replace. Look for a split or cracked vacuum hose but that may not be big enough at get enough air to race the motor that fast . Check your water temp sensor. Check the hot wax rod system and idle cam .

 

hey thanks a lot for responding I appreciate it. After further inspeciton today I found the problem the throttle body gasket ripped. Anyways thats where the air was sucking in. Fixed it. But thanks for the tips.