Rep Power: 0

Ok, so I just bought this 1997 civic LX 5 speed 2 weeks ago, a great car over all, but it has its quarks, and I am usually pretty good with cars and diagnosing a problem, but this Honda has me baffled, I am not very familiar with imports..

When I start it, it sits at about 1300RPM on a winter morning in Minnesota, but as soon as I put it into gear and move it the idle jumps to 3000rpm, like instantly, I can literally throw it into gear move 50ft, put it back into neutral and its at 3000rpm solid and does not move. If you turn off the car and turn it back on, the same thing will happen after you put it into gear move it then take it out, but if you warm up the car to operating temperature by driving some, then pull over and turn it off then on, it stops and is fine then idles at about 1300rmp all day, even if you turn it off and go into a store, as long as it is still pretty warm, it does not happen..

Any input would be greatly appreciated..

 
Rep Power: 234

Check for a vacuum leak. Rubber shrinks when cold and expands when warm. That's why it idles fine when warm and not so fine when cold.

Your IACV could also be sticking. Try cleaning it.

 
Rep Power: 0

Also my cruise control speed fluctuates, I set it at about 60, it goes anywhere from 65-55 on its own.. any specific cause??

Any links to write ups for the IACV cleaning for my car?

 
Rep Power: 189

Cruise control will fluctuate anywhere from 5-6 mph usually so long as it kicks back in for you its normal, you can check the cable see if its overly loose same for the throttle cable and readjust it to take the slack out. If it fluctuates more than 10 mph that is when I would be looking into it.

 
Rep Power: 0

Hey I cleaned my iacv with carb cleaner let it dry, put it back together, and now its worse when im not in a gear the idle fluxuates between 1K and 2K in a rythmic sweep up and down, now what??

 
Rep Power: 189

Did you use all new gaskets? Might be a good idea to check along the intake manifold for leaks by spraying with carb cleaner or throttlebody cleaner along the seam see if idle takes a sudden change.

 
Rep Power: 0

No, I didn't use new gaskets, but it seems to only do it when its at operating temp, idk if that changes anything, from a cold start its great now, warm its bad, the exact opposite as before..

Recently, like a day before I cleaned the IACV I installed a stereo system and had the battery disconnected for a bit, I hear for Honda's you have to "re learn" the idle for the ECU, should I do that and see what it gets me??

 
Rep Power: 189

I have had to disconnect my battery a few times, stereo install, remote start with keyless entry install, sub/amp wiring fix, never had an issue and yes not using new gaskets can make a difference vac leaks can be hard to track sometimes and hot/cold can make a big difference, metal expands or contracts with temp variation this can open or close a vac leak. I would check the resistance on teh engine coolant temp sensor (should be a 2 wire sensor in the thermostat housing) do it when cold and when hot see what it reads. Here is the idle relearn procedure;

 
Rep Power: 0

The coolant resistance sensor?? I have no clue what that is.. or how to "test it"

The filter box isn't exactly perfectly seated on there.. its kinda half *** on there, probably causing a vacuum leak, ill re seat that tomorrow and see if it changes anything...

 
Rep Power: 189

It won't make any difference vac leaks in or after the throttlebody will.

 
Rep Power: 0

I appreciate your help, I took off the throttle body, the gasket was slightly creased on one corner, I flattened it out, re seated the TB, tightened it tighter than before, and got the air box plastic ring on their right using some lubricant, and it works fine now, took it for a 30min test drive, and it runs great, and smooth. I am sure the IACV was the issue at first, but not being put together properly was my fault, anyway thank you.

 
Rep Power: 189

anytime, glad you got it all working well.