idles higher as it warms up (2500) 600 at startup

[92tsifwd]

My car idles at 600rpms when i start it and as it gets warmer it slowly climbs until about 2500rpm and stays there the whole time driving it. I have swaped two good iac motors and no change checked my idle switch and tps % I have not checked the ecu but, I'm going to swap with a good one today and I'll post my resalts. Any ideas?

 

[Batmobile]

vacum leak?

 

[eclipse90gsxt]

Vaccum leak will usually make the idle higher. I would make a leak tester and see what happens.

 

[heavyD]

Sounds like a vacuum leak. It could be the manifold gasket or TB gasket if it leaks at operating temps only.

 

[gump1976]

hi my car did the same thing, but didnt go as high, but it would take like a half hour and it would go all the way to a 1500 idle. seemed as if as it got warmer under the hood it would raise. I found my throttle cable was tightening up while i was driving so I gave it some more slack where it connects to the intake manifold, as well as where it feeds into that box mounted on the firewall, there are like 4 12mm nuts there. Try maybe giving the cable a little more slack and see what it does for you. Good luck.

 

[92tsifwd]

I tried the known to be good ecu and no success. It is idle surging now also. The only thing I have not checked is the tps and throttle cable by the box.

 

[92tsifwd]

Sometimes when I rev the engine it will stay where I rev it. I will do a boost leak test tonight.

 

[steve]

It is idle surging now also.

I was surprised it wasn't surging before, maybe it wasn't seeing the IPS close.

Steve

 

[92tsifwd]

I checked and adjusted my throttle cables and no change. But I noticed that when it revs up and down the fuel pressure solinoid clicks on and off at the rate of the idle surge. So I am wondering if this may be bad?

 

[tim_korn_99]

I'm 100% sure that it's your FIAV that is the cause of your problem. My car did the SAME thing, and after trying everything, i finally blocked off the FIAV as per instructions from the VFAQ, and it fixed my problem.
When you do it, make sure you re-route the coolant lines together.
-Tim

 

[92tsifwd]

I got a used tb and it was said to be in perfect condition. I did not think it was that but I will try blocking off the fiav tomarrow. But it is cold here and I would not think it would idle when cold.

 

[92tsifwd]

Tonight I made a blockoff plate for the fiav and the isc. Will it still idle fine with the isc blocked off also? Or do I need the isc?

 

[92tsifwd]

I blocked the fiav only and it idled for a while and then began to idle surge again. So the battle continues. No idea what so ever what is causing this?

 

[92tsifwd]

It is smoking it idles at 2500 and revs up and down now. So any Ideas are helpfull.

 

[steve]

INo idea what so ever what is causing this?

I'd still go with the answer in posts 2-4.
You have a leak somewhere. Since blocking off the FIAV didn't fix the problem, that wasn't it. I'd put it back the way it was and start pressure testing the intake. Don't forget to correctly set the BISS once it's back together. If it's misadjusted you can get surge.

Make sure the ECU's ISC circuits are good, Try turning on the AC and make sure the engine idles up and then back down when you turn it off.

Steve

 

[92tsifwd]

I found the problem guys. I simply unpluged the iac motor and idles solid at 800 all the time. Strange, the iac motor seemed to work fine on my buddy's car. It is from a 90 so, mabey there is a difference. Will it hurt anything leaving the iac motor unpluged? I don't have any money for a new one for a while. Thanks.

 

[t0taleclipse]

I found the problem guys. I simply unpluged the iac motor and idles solid at 800 all the time. Strange, the iac motor seemed to work fine on my buddy's car. It is from a 90 so, mabey there is a difference. Will it hurt anything leaving the iac motor unpluged? I don't have any money for a new one for a while. Thanks.

i have the same problem with my car. When it did idle fine i unplugged the ISC and it idled great now but one thing. Its doesnt idle high when its cold. Does yours idle higher at cold start ups with the ISC unpluged????

 

[92tsifwd]

No, it idles a little low when apliing the brakes or turning on accessories. Not shure if it effects gas millage also?

 

[t0taleclipse]

So my problem is the ISC. I thought the FIAV would of been bad too and i'd have to switch to the FIFV (FAST IDLE FOOT VALVE) and warm my car up holding the gas. So you also have the cold start problem to then with the ISC unplugged. Maybe we should just order new ones, they are only like $80.

 

[92tsifwd]

Ya, it sucks when it is blizerding cold like it is here because it wont stay running by it self till it warms up. A new isc wont help cold start ups though. Its just there for when there are loads on the motor it kicks the idle up. It might help getting one though.

 

[steve]

A new isc wont help cold start ups though. Its just there for when there are loads on the motor it kicks the idle up. It might help getting one though.

Actually, if you read the 1G technical manual or watch the ISC steps during starting you'll find out that the ISC is used to aid in starting all the time.

Steve

 

[t0taleclipse]

Thats what I thought because my car had idle surge and a high idle but when it did idle fine I pulled the ISC connector. No more idle surge and if it was the FIAV it would still surge. So yes the ISC does aid in start-ups and it will effect cold start-ups like the FIAV would.




See this question was not answered on any other forum but now I'm glad it out here for everyone else. Thanks guys.

 

[2GeNTSi]

Eh I don't want to type this all out so here's a copy from another thread I posted in.

...Now my dilemma now is similar to the thread starter. When I start my car in the morning, the rpms will start out low (about 800) and then rise up to normal initial rpm idle. I usually just let it warm up til it's just above C, then I'm off but everytime I stop until it is fully warmed up, the idle will be a little lower then usual (most cars at this point would have the rpms still high because it is not fully warmed up). When it is fully warmed up and I come to a stop afterwards, everything is fine. Though lets say I go to the store and come back a minute later, when I start it, the rpms will again start out low... (even if I just shut it down warmed up) but it'll be fine once I get going.

So like a lot of you guys are mentioning, I believe it might be the IAC or the TPS...some throttle body related part, so when I do my timing belt job during spring break, I'll go ahead to clean it out and test both sensors.