My 1988 CRX Si with D16ZC is having an idle problem that just showed up. Its quite intermittent (only happened twice so far) and what happens is only sometimes when the engine is warmed up fully and idling, the RPM will drop maybey a few hundred RPM, then go straight back up to normal idle for a few seconds, then back down again. It stops if I touch and release the throttle.

Where should I start looking? It doesn't seem to fit the fault description of any of the idle control valves as these can only cause idle to increase.

Thanks

 

try to loosen the throttle cable a little...!!!

 

Idle control systems can also cause fluctuations.

 

The throttle cable is properly set, with slack when idling

 

They wouldnt cause idle to drop below the base idle because this is set by a screw, so even if the control valves were fully closed in fault the idle cannot go below base idle speed.

I still intend to at some stage have a look at these for the sake of good maintenance, but I would like as many suggestions as possible to help in narrowing it down.

Thanks

 

Though your base idle might be set at the 'couple of hundred rpm lower', and the idle control system might be boosting the idle at other times.

Do you have an FITV or dashpot booster controlling the throttle plenum? My ZC came with the later, and i was having similar idle issues, i tried a different dashpot which didn't work so i swapped on an OBD1 manifold and throttle body which runs an FITV and it idled beautifully.

 

How would I ascertain that?