Honda question about idle surge

[john]

I am thinking about getting a 95 civic at an auction. Body is in shitty shape but I am just looking for a reliable car. The only problem I have come accross is that it has idle surge. The car idled about 2k when I started it. I reved it slowely to roughly 4k to hear how the engine sounded. When I got off the throttle, the idle surge happend. It seemed to lower (in rpms) when the car started to warm up but it continued to idle surge non the less. I am familliar with how this happens to dsms but not anything else. It usually has to do with a vaccum leak or the ISC going out. What causes this on a honda? Please help ASAP as the auction is tomorrow night. Thanks in advance, John.

[MATCHBX]

Running at 2000rpm at cold start up is normal for a Honda. After it warms up it drops down. It should idle around 700-800rpm.

If it starts idling up and down more than 500rpm after it's warmed up, it is usually a sign of air in the coolling system. Usually caused by a bad shaft seal in the waterpump or a bad radiator cap. I have encountered this problem in my Honda as well over the years. They can sometimes be a pain in the butt to get all the air out after changing thermostats or draining the radiator and refilling it.

If left to run like that for about 10 or 15 minutes, it should start overheating. Next time, just because it's revs at 2000rpm at a cold start up, don't rev the piss out of it to try to get it down to a lower rpm. You'll do more damage than good. Next time let it warm up to operating temp before you starting raising the rpms.

Edit: I know you said you slowly revved it, but you shouldn't ever rev a cold engine so high until it warms up.

[x1genx]

well it could be a couple of things...check the iac (idle air control valve)...it may have a map sensor issue also. If the cars never been messed with you wouldnt have to worry about fuel map issues...or maybe it could be a valve timing issue dependin on the motor sohc vtecs. Just what I can think of off the top of my head but your light years smarter than me but if you missed checkin that stuff start there.

[john]

It had idled for a few minutes and I was in a hurry. I slowely reved to see if I could hear anything out of the ordinary. The car has never been messed with. Thanks for the help.

[Shane@DBPerformance]

Often it is the same problems as DSMs. Vacuum leak or idle air control motor. A leak after the TB can cause it to do it and their idle motors can have problems too. Also, if the TPS sensor is not calibrated right, then it can have idle problems. If the car hasn't ever been messed with, then the TPS shouldn't be a problem. Running too lean at idle causes idle surge also, but if the car isn't modded, then the fueling should be okay.

[john]

Thanks.