Hey guys,
I have an 89 pickup with a 22RE out of an 94 in it. The temp gauge hadn't been moving and it had been idling high for quite a while so I recently replaced the thermostat & solved that problem however I now have a surging idle problem. At idle it will bog down to the point you think it's going to die but then it surges back up. It doesn't die & runs fine when given gas, but then goes right back to surging when I let off. I've done some searching and this seems to be fairly common from what I've seen. I pulled the throttle body/IAC off (my throttle also sticks) and will be cleaning them today. From what I've read the IAC could be the cause of the surging, what is the best way to clean the IAC valve and how do I know if it needs to be replaced instead of cleaned? Also if this dosn't take care of the problem what do you recomend for my next steps? Thanks.

 

If the cooling system is not full , it will cause exactly those conditions , check your coolant level again now , you may need to top it up .


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there's air in the system, take the coolant camp off, leave it off and let the engine idle and at times rev it up some, when this happened to me took about 20 minutes for the idle to get back to normal

 

Improper coolant levels or air pockets cause the engine to surge higher, eg when the pump hits the air pocket it revs up.

Throttle body/carb cleaner, plastic brush. Not sure where the tests are located in the manual if there are any, sorry.


Autozone autoshop101 yotatech There are also several youtube videos for cleaning them.

You can't really test them with out special equipment to drive the coils. You can manually move the plunger this will test the spring return(assuming it has one). Or try blowing air thru it to see if it's sealing. Another obvious reason to replace it would be if the Ohm reading of the coils indicated open circuit.

My suggestion would be to clean the temp sensors off, which you could do with a scotchpad and maybe a scraper or steel wool. You can Test for a dirty sensor by unplugging it when it's surging and it sould switch to a default/fixed temp in the calculations.

 

This is a rather obscure occurrence, but you may find the fault in your spark plugs. My thermostat acted up a while back and it cooked my plugs. I couldn't explain how this affected the fluidity of the engine, but I can say fresh plugs fixed the problem. This may be just as possible, but not probable, perhaps.

The other suggestions above are a great step and they should eradicate your troubled RPM, but I figured I would give what information I had.

Good luck!