89GXL..I asked this too many times but got no ansewers except for a ( it could be timing) So can it or cant it? Another thing..After I rev it really high like 8k rpms and let the needle drop , the idle will fluctuate for awile up and down but most of the time DIE. Whats up?

 

maybe it's your idle control switch.

 

The two most likely suspects would be the thermowax, which increases idle speed when the engine's cold, or (less likely) the coolant themosensor, which tells the ECU the coolant temp so it can adjust mixtures to suit. There are procedures in the FSM for testing both of these.

 

Similar to this page from a 87 manual. Yours will be slightly different:

 

Second part:

 

So mabey if it was my thermowax then I can take it off and prob will go away Yes??? If not I will look at the fast idle cam and mabey buy a thermosensor...ITs the one that goes on top of the radiator right?

 

Um, no! If it's not working, how will taking it off fix the problem? If you want the fast-idle system to work, you'll have to fix it, not remove it.No, thats the coolant level sensor. The coolant thermosensor is on the back of the water pump, under the alternator. Test it before you replace it (as per the FSM), it's not that cheap. Check the fast-idle system first though.