Got an 89 Civic dx that after it warms up loops or surges until reved up. Just put new head gasket on, swaped ecu, checked all vacuums, replaced pcv, changed fuel filter, air filter is clean, and have checked most other things. Only thing I haven't changed is the EACV(IACV), and when bypass hose to intake is clamped, idles normal. Any suggestions?

 

Are you saying at idle the needle jumps around at dif rpm's?

 

Well this model doesn't have a tach, so can't give specifics on range, but it does idle up and down on its own after warmup. It also does it at a fairly fast pace, with variations every couple seconds or less. Like I said above, you can increase throttle and it plains out, but as soon as you release it starts cycling again.

 

So does no one have any ideas, or does no one know what I mean by "looping idle". Basically, I'm having the same problem that the guy with the engine reving up and down, except different engine. I figured that being an older model surely someone in this world has came across this same problem. Used EACVs seemed to be hard to find, and the cheapest aftermarket I can find is at Autozone for $209.00. Sure would be good to have some second opinions before I buy one.

 

might have something to do with the clutchor the tranny? I dunno don't quote me on that. Is it a manuel or auto?

 

I had a problem like yours but on my 95 civic and it turnd out to be the fast idle thermo valve. Not too sure if yours will av one with it been slightly older but its worth a look in.

 

Sticky throttle plate? Perhaps your throttle plate is coated with gum, as it warms it becomes less tacky. There is also the throttle position sensor(if yours has one), not sure how to test(haynes maybe).