idle is off, engine takes forever to heat up.....HELP - Honda Prelude Forum

my project lude · 03-16-2010, 05:37 PM

So I bought my new girl from a repo. The revs were going about 1500 up and down but the engine sounded good and had some good mods on it. Price was right and I bought it. Crazy things after that. They had put a peice of electric tape over the filter for the IACV, one bolt holding in the distributor and the cap, NO oil, and header gasket blown out. So I went through and changed all these things except the gasket (on order), and here is where is gets really weird. I changed the oil on the car and had it on Jack stands. Start the car, while on stands, and the idle is perfect. Lower the car and restart it.....you guessed it, idle returns. The other thing is the engine will not heat up. After driving it for about 15, 20 minutes the engine is still cool enough for you to touch. My first H22 so maybe that is there thing, but I son't think so. I know there is a Lude junkie out there that has seen this before....HELP!!!!!!

Kronn 98SH · 03-16-2010, 06:39 PM

Temperature is controlled by thermostat.

my project lude · 03-16-2010, 10:35 PM

I know the thermostat controls the heat of the engine. If it was letting to litttle in it would be overheating and if it was screwed up the temp guage would start bouncing around. I didn't know if it might be worn out letting to much coolent in. Only problem is when I took the IACV off there was not much coolent in it. So, either I was expecting more coolent then was in there, there is too much coolent going in where the spring on the thermo is worn down, or there is something more to it that might possibly involve the engine crazy idle. It's the crazy idle that really has me screwed. That and why having it jacked up would fix the idle.

one more detail that may help, when I get on it when driving after about 3.5, 4 grand it feels like it wants to launch, but something is holding it back. Not like it i s bogged down, just not moving. Like it might be running lean?

indylude18 · 03-17-2010, 07:49 AM

Air in your coolant lines could cause bad idle....

Glaucus · 03-17-2010, 08:07 AM

Yep, most likely air in the coolant. Makes sense as a bubble can cause the bad idle. And the engine is warming, it's just the bubble is preventing the heated coolant from circulating to the temp sensor that goes to your dash (the thermostat that controls coolant flow may actually be open but there may not be enough force to push the coolant through a large air bubble at a high point in the system). Putting the car on jacks would allow the air bubble to shift, which may improve your circulation and fix your idle problems.

So now, why would you have air in your cooling system?

my project lude · 03-17-2010, 02:58 PM

It all makes really good sence!! Glaucus-you are the man.
Why would there be coolent in the line? I am guessing because I bought this car on a repo. There was some blots loose and missing. You know where I am going....either they had a built motor and threw this one in to keep from loosing the built one when they got behind, or some kid had got hold of it and jacked up something simple. It's not loosing coolent, so it's not that bad, but a bubble would fit the perscription perfect!! Thank you so much!!!

I am supposed to have some good wether this weekend, I will get back and let you know how it does.

indylude18 · 03-17-2010, 04:05 PM

It is possible that the last owner just "forgot" to bleed the cooling system when he installed something. Just bleed the air out of the system, fill to the correct level with coolant, and see if the problems return. My guess is that they won't...The P.O. probably just half-assed it when he was "fixing" something.

my project lude · 03-17-2010, 04:43 PM

ya, it sucks not seeing the hands it came from, but i imagine the nose to be big, red and round. I am going to check the fast idle while i am in there. It tottaly slipped my mind, but I think the coolent is definetly the main issue. It just fits. I will keep you guys posted.

my project lude · 03-24-2010, 01:48 PM

So I replaced the thermostat on the lude, and it helped the idle, but it is still idleing up and down. I felt the hoses and it doesn't feel like any pressure is building up. I am going to take it on the interstate and see if I can build some pressure and blow the air out that way. Still has air in it (I think) because it idles fine when I first start it up and then starts to idle off. Which makes me think the FITV needs to be cleaned and/or adjusted.

Now, next problem, the tach has to be off. Sounds like the engine was reved up way past what it was reading. When the key is out the RPMs sit at 1200. It will go down after the engine is running, but not much. Any ideas of how to adjust the tach? I think the speed is right. The cat that owned it before me must have had the dash out.