Idle Issues Please Help!!!

[redgst95]

it just started doing this yesterday my car would not idle under 1k for nothing for a while last night. when i finally got home it was back to normal (750),today my car is idling at around 680 or less. when i turn the ac on instead of the rpms raising they fall?! when i get up to higher rpms and push in the clutch the rpms fall to almost zero and the car boggs and then comes back up to idle. also when i start the car it idles really low for a sec the raises a little. what could be causing this? it just started out of the blue! i really need some help cause i dont know if this is something i should be worried about or not....but i know its not normal!!!!thanx

 

[RavenX]

Most likely your ISC went bad so check that out first and swap it with another friends ISC to rule it out. If not then you have to check the FIAV or the BISS. Its one of the 3

 

[oldman]

Make sure the intake pipe couplers on both the mas and turbo side are ok. Also check for boost leak.

 

[yell-O]

i had the same problem, my car was idleing bad. After reading alot of posts on here, i figured it is the IAC.
Is your car's RPM swinging from 500-2000 rpm? or going up and down. Mine did.

However, this is how you could check/ temp fix the problem (if your car's RPM is swinging up and down). Locate the harness for the IAC motor, its right below the TB. Start your car and when your car seems to be at the normal range RPM, take the harness off the IAC motor. So now your IAC motor is not working and the rpm should be not be floating up and down. I hope you get the idea. Do what other people on here tell you to, try mine as the last resort.

 

[redgst95]

thanks for the information but what do i need to do about the rpms falling to almost zero everytime i push in the clutch from higher rpms?

 

[oldman]

thanks for the information but what do i need to do about the rpms falling to almost zero everytime i push in the clutch from higher rpms?

My car would die when I press down my clutch when my intake to turbo coupler poped off. When you fix your idle problem, you'll most likely fix the clutch/rpm problem as well.

 

[hewhoisknot]

i had the same problem but it would actually die on me, i'd cruise in neutral and she would die, turned out to be the coupler on my intake pipe to the turbo, check all couplers and do a leak down test...if it fluxes it is not the BISS,

 

[redgst95]

did it only die when u have the a/c on cause thats what happens to me! itonly happens when the a/c is on!!

 

[95 'clipse RS]

ok i have one of these problems i think... except my car on cold start idles 1500 then slowly edges its way to 2100 sometimes 2300, the times when it does reach that far it falls quickly to about 1300 then back up to 2100-2300. ive checked the iac cleaned it, replaced it with one from a j yard to see if any difference at all and none. i aslo checked the egr valve and it seems fine. i pulled the code and its like P0505 i think, but i know it said it was in the idle air control system. my car is a non turbo, so...any ideas??

thanks for your help

 

[95 'clipse RS]

ok i have one of these problems i think... except my car on cold start idles 1500 then slowly edges its way to 2100 sometimes 2300, the times when it does reach that far it falls quickly to about 1300 then back up to 2100-2300. ive checked the iac cleaned it, replaced it with one from a j yard to see if any difference at all and none. i aslo checked the egr valve and it seems fine. i pulled the code and its like P0505 i think, but i know it said it was in the idle air control system. my car is a non turbo 420a, so...any ideas??

thanks for your help

 

[2.4 turbo Hyped]

95% of the idle problems I have found are related to unmetered air entering the engine. Do a very very thorough boost leak check and get back to us.

 

[95 'clipse RS]

mine is non turbo though

 

[RedRain]

http://crebotech.com/page2.html
http://dmtalon.v8eaters.com/ISC.html

Theres 2 sites that will tell you how to test ur ISC, Im planning on purchasing a rebuilt one from Crebotech.com. I have a 92 Eclipse and a 92 Talon. Both are surging and I tested them and they both have resistances between 22-38 ohms. Too low and Too high. Ill purchase one and swap them on both to make sure though. Make sure to test them before replacing anything yet though.

 

[95 'clipse RS]

mine is 95, does it still have it and where would it be??

 

[RedRain]

I believe that it is right below ur Throttle Body, but im not really sure since u mentioned its a 420a. Check around the Throttle Body area for some connectors.

 

[95 'clipse RS]

i took the tb off earlier to clean it free of carbon, there are two sensors on it, an idle air control valve and some other sensor, when you take the second one off it reveals a bearing and a shaft that rotates from the butterfly, i dunno what that one is. but there ar two on the tb.

thanks

 

[RedRain]

Yea check the Idle Air Control Valve, the ISC and IAC are the same thing. Just different names I believe in the 1g's and 2g's maybe, dont really know, but ive heard these are the same though.

 

[95 'clipse RS]

ok heres the deal with the IAC, ive had it out like 5 times to clean it and put back in, recently i just took one from the j yard and put it in it, but it doesn't help. i unplug the sensor when running and it doesnt make a difference. so i dunno if it is working or not, how can you tell easily?

thanks

 

[95 'clipse RS]

oh, wait a second, im comining to the conclusion that it is a massive intake manifold leak, all of my vaccuum seem fine, but at a 2100rpm idle i can put my hand in front of the tb opening, now that should suck my hand a little, but its barely doin any at all. i have no clue where to even start, so could anyone lead me in the right direction??!?

thanks all

 

[oldman]

Stop guessing and do a boost leak test already.

 

[95 'clipse RS]

and once again non turbo.....

 

[95 'clipse RS]

uh...yeah.... thannks for your help... but it seems no one has really had any experience on this type of problem... it was an intake maniflod gasket..and once again non turbo... but yeah a bad seal can make idle that high. well see ya noobs

 

[2GeNTSi]

A gasket can make the car idle really bad. When putting my car back to stock a while back, I was putting my stock upper ic pipe back on and when I did so, the gasket in between the tb and the intake manifold swung down and was just hanging there. I couldn't figure it out for days what was going wrong until I decided to take out the tb and check the iac, but I noticed after I was almost done taking it out, that the gasket was just dangling which turned out to be why it would idle like crap.

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. 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. 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 to get in my car, 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.