[671blaze_it71]

My car just started doing this today. when im at a stop or at neutral it will idle up to 1500 rpms and drop to like 500 and will jump back up to 1500 rpms repeatedly anyone know whats wrong with it really need help

 

[shadowcrx]

i would think to try the little resistor box first, if not then i would suggest a tune up those are always good anyway

 

[jfrolang]

possibly the ignitor.

 

[ZeniceguyCRX]

1 check you pcv vale
2 check to make sure your coolant is full it an cause it aswel
3 try adjusting your idle controle screw up a bit.
4th and last but do it first is check to make sure your not throwing a iacv code on the ecu

 

[bobski]

What year and model is it?

 

[671blaze_it71]

it is a 1990 si

 

[fireant]

Can you get a code on the ECU without the Check Engine light coming on?

 

[ryan_long_01]

You can always try resetting the ECU -- with your car already warmed up (do this after a drive), just pull the hazard fuse (it's in the engine compartment fusebox, not the one in the cabin...some people pull the ECU fuse also just to be sure), leave it out for a minute, pop it back in, and start up the car. Don't turn any accessories on, and don't touch the accelerator. Your car will start out idling high, and slowly work its way down to a nice, smooth, low idle. Let it sit there for at least 10 minutes or so before turning the car off. This usually fixes any little idle problems that aren't the result of an ignition problem, bad sensor, etc.

 

[bobski]

I would try cleaning the EACV first (Electronic Air Control Valve, later renamed Idle Air Control Valve). Grab a can of carburator cleaner, remove the air intake hose between the throttle body and the air cleaner box and look in the throttle body. You should see a hole in the rear interior surface a little before the throttle plate. Attach the little straw to the nozzle of the cleaner and spray short bursts into that hole. The engine may try to stall... The idea is to keep the bursts short enough that it doesn't. After you've done 15-20 bursts, spray a solid stream into the hole until the engine stalls. Let it sit and soak for 10-15 minutes. Restart the engine (it may take a little cranking) and immediately go back to the short bursts. The idea here is to flush out any deposits that the soaking broke loose... 10 sprays is probably enough. After that, either do another long spray & soak, or take it for a drive to see if the problem's fixed

 

[Neil]

How is driveability? Do you have WOT? When I had this problem it was a plugged fuel filter. I tried all the things that are suggested above, and none worked.

I was throwing an O2 sensor code.

Replaced the fuel pump cause my fuel pressure would drop when you'd snap the throttle. Put higher volume pump in, turned key on, blew fuse. Figured it was trying to push the fuel, but couldn't. Changed filter. VROOOMMM!!!

Hope I helped.