I have a 1991 Honda CRX with a d15b2 engine, manual transmission and Dualpoint injection. When I start the car, it has an idle at 1500 rpms. Once its warmed up it bounces up and down between 1500 and 900. I have cleaned out the Idle Air Control Valve and it didn't do anything to it. I'm new to this mechanic stuff so please explain it thorough to me what you think the problem is, otherwise I have no idea what your talking about.

Any advice or tips is much appreciated.

 

Could be a dirty idle air control valve, Could have air in the cooling system, could be a vacuum leak, i would start by making sure the cooling system is full, that would be the easiest place to start. Notice any leaks or smells by chance?

 

I've cleaned my idle air control valve and it did nothing different. Where do I check for leaks? and as for smells, its just a collage of different smells when driving. Mostly a strong oil smell, but I'm not losing any. Ill try bleeding the cooling system tomorrow.

 

Where does the idle sit if you unplug the IACV? Just disconnect the harness plug and the bouncing should stop. If the idle without the IACV connected is considerably higher than 1k, you're going to get bouncing even if it's clean (with the IACV connected). You can adjust the throttle bypass screw to lower this to ~700rpm. If you screw it all the way in and it's still high, you're probably looking at a vacuum leak.

You can search around for a vacuum diagram for your car and spray carb cleaner at the connection points to locate leaks.

Another thing it could be is the FITV (https://honda-tech.com/forums/acura-integra-6/%2A%2A%2A-how-%2A%2A%2A-clean-your-fitv-aka-fast-idle-thermo-valve-1564019/). I don't have experience with this since I have an HF which does not have one. If you disconnect the IACV and it's still bouncing, I'd guess it has to do with this.

If you need more info on any of the stuff I mentioned, you can search and there's tons of tutorials on here.

 

AlexK47, thanks much! I just went outside to try unplugging my IACV and when I did the car immediately dropped to 800 but continued to bounce between 800 and 1000. So I replugged it in and adjusted my Throttle bypass screw, when turning it right it began to raise my RPM's, then I turned the screw left everything just went back to 1500. BUT as I tried putting the plastic cap back on the screw my hand bumped into the throttle cable and lowered the RPM considerably, all I had to do was loosen the cable and it all went to normal, 750 and stable. Cant believe it was something so stupid.

 

there is no FITV on this car FYI, Glad to hear ya got it sorted

 

Brizzle, yeah I wasn't sure which models had the FITV. Thanks for clearing it up.

Banshi, great to hear it's fixed. Yeah, there are a million things that effect this. I had the EXACT same problem with the throttle cable being too tight. Totally forgot about that.

 

^ +1