2001 Civic HX - Intermittent High idle? (Won't enter lean burn)
 

A wierd problem just cropped up on my Civic yesterday. About 2/3 of the time, it will idle at 1400rpms, the rest of the time it bumps back down to it's normal 600rpms.

I recently got a "Pending trouble code" on my Ultragauge (awesome feature, BTW) of P1456 which translates to an Evap system leak, tank side. This is typically a gas cap issue, so I removed the gas cap and put it back on and haven't seen the code since.

Since this started, I haven't been able to get it to enter Lean Burn.

Also, I recently removed my power steering belt, though I don't see how that would be relevant.

Any thoughts on tracking it down?

My first thought is a vacuum leak, but being intermittent puzzles me. Evap system could cause it to be intermittent, but why am I not seeing the code come back?

Check the engine coolant temp. Can the UG display it constantly for you? If not warming up and staying warm it might idle fast. My HX had a bum t'stat when I bought it four years ago. They can be sticky but don't know if it would cause fast idle. Easy to check though.

Thanks for the suggestion. It's something I monitor, but it's not on my primary screen. I'll keep an eye on it and look for anomolies.

My idle was all over the place before I cleaned out the EGR passages

EGR is a good suggestion.

Also, how's your exhaust manifold and/or O2 sensor? I had a crack in my manifold at the sensor port and it would sometimes idle high like you describe.

Hmm, I keep hearing about this with Honda engines and I doubt anyone has ever done so with this car. Is there any way to confirm the EGR system is clogged before opening it up?

Full factory service manual just showed up, so I guess I'll check there too.

Nothing unusual about the coolant temps.

yes, either with your mouth or vacuum pump pull a vacuum on the egr valve actuator diaphram, so it with the engine idling, if the passages are good the engine will sputter really bad from the exhaust gas being injested meaning you have open egr passages.

However the HX has an electronically controlled EGR valve, has no vacuum hose going to it. Not sure when the Civic line got away from a vacuum controlled EGR. HX model began in 1996.

Then, reassemble car and run off cliff. buy obd 1 civic.problem solved :D

I just opened egr passage block up. It took two nuts to allow the fuel rail to move out of the way, then maybe 5 bolts on the passage plate. After that I could quickly see it was the problem. There might be other ways to tell, but it only took me 5-10 minutes to get in there and look at it. I did a write up for the and linked to an even better write up with labeled pictures. Hopefully it is similar to yours.