AC/Idle Problem

Before I get flamed, yes, I did do a search on the topic and my situation is slightly different....bear with me as I want to be as detailed as possible...

Okay, so I was driving today and it was hot so I decided to turn on the AC since my parents always bash me for not using it. I turn it on for about 10 minutes and when I arrive at my destination, my car just dies. I turn off the AC, start my car and my idle just goes up to about 1.5K and drops and just dies again. It does that a couple times and I somehow manage to park my car so I go out and check a couple things: brake fluid is full (because my brake lights came on), MAS is snug, engine oil okay.

Well, I keep trying to start it and it won't hold and noticed that I always keep my clutch down even after my car started up...so what I did was start up my car and released my clutch really quick. My car shakes a bit as it tries to gain some type of idle and it eventually does--really low at about 500. I let it warm up a bit, the idle still around 500, and then start driving home. The whole time while I was driving my idle would just idle randomly: sometimes at 500, sometimes at about 200, and sometimes normal at around 700-800. I was trying different methods as I was driving home to see if I could get it to idle properly during stops--holding the clutch down, releasing the clutch, holding the brakes, releasing the brakes, and combinations of the two. I tried everything and there was no pattern/explaination to its random idles so I concluded that it was just that....random.

When I arrive home, I do a couple more test but this time, with the AC. I start my car and it idles randomly, I turn on the fan and as soon as I push the AC button, my car just shuts off. I tested that about 3 times and everytime it does the same thing. I stop for about 5 minutes and then try it again: start car and it idles about 600, turn on the fan, then when I turn on the AC the idle drops to about 100 but the car is still on. It's on for about 2 minutes but when I turn the AC off this time, my car dies. :banghead: Just when I thought I was getting some type of pattern everything goes back to being random.

Okay, so I come in and do a search and some reading...

1-my AC belt was changed about 2 years ago so I don't think its that. It was also tight on the pulleys so I think it's okay.
2-my plugs and wires were replaced about a year ago: stock plugs with Accel wires.
3-a couple members mention the IAC and I have that out right now but haven't fully cleaned it up yet since I don't have any electrical cleaner at the moment.

So there you have it...help!?! Besides the IAC, what do you guys think it could be? Also, I wasn't planning on opening the interior of the IAC like Jeff Lucius to clean it and was just gonna clean the exterior...do you think it'll be better if I just did both?

I don't know when the battery and alternator was last replaced but seeing that I was able to drive home for about 20 minutes, I don't think they are the problem.

Finally, the last thing that was done to my car was when I got it smogged about a month ago. The guy took off this one piece and the car started to shake really bad but then he put it back and everything thing seemed okay. I couldn't see what he took off but I think it might have been some tube because he pulled off those little tube clamps that are usually on rubber hoses (he was on the passenger side when he did that)...don't know if it has anything to do with my situation but I just remember the shaking of my car.

Okay guys, any guidance you guys could give me would be greatly appreciated. Thanks for the help fellas...

first off, definitely check the IAC. and i would disassemble the whole thing, clean it inside and out, then reassemble. electric parts cleaner? brake cleaner works fine. anything with a high vapor pressure so it evaporates and doesn't linger.

secondly, although everyone likes to quickly rule-out the battery and alternator, these two components are the most common adn thusly are the most problematic. easiest way is to take your battery to autozone (or a local parts chain) and they should test it for free. they should also do this with you alternator, but its not fun removing that b/c you have to remove the belt.

but when you press the A/C button, the idle drops adn the car dies, that leads me to believe that its battery related, not alternator related. but i could be wrong b/c those two are always a sticky area as to what causes the other to do what.

so battery, IAC, then let us know.

UPDATE: This morning I went to Kragen and bought some electrical parts cleaner and cleaned the outside of the IAC. I tried opening up the interior as well but the 3 screws won't budge and I don't have the bench vice like Lucius so I just stopped seeing that the screws were beginning to strip. After I cleaned it, I let it dry for a bit and put everything back in. I go to start my car and my idle goes up and comes down and the car dies. Did that about 4 times and then I wait for about 30 seconds, start it up and it struggles and shakes as it tries to get some type of stable idle....finally does. Everything looks normal and I let my car run for about 15 minutes to let the ECU relearn everything. After 15 minutes, I decide to take it for a test drive and on my way down the driveway, my idle drops to about 200 again so I just stop and come back up. :( By this time it is idling at about 600.

I try my AC and when I turn it on, my idle drops to about 400 and when I turn it back off, it goes to about 600 again.

Any thoughts guys? :( Linebckr49, I'll bring my car over to AutoZone later today to see if they could test the battery and alternator for me. Thanks for advice. They should be able to do both inside the car, right?

UGH, this is so frustrating....if anyone has any other bright ideas then I'm all ears. If it's definitely the IAC, I'll just suck it up and buy a new one seeing that my car's a daily driver and I can't afford to have it out of commission for an extended period of time. I'll post back after I get my battery & alternator checked. In the meantime, any other ideas would be greatly appreciated. Thanks guys!!!

Okay, I just got back from AutoZone and Kragen:

1-AutoZone tested both the battery and alternator and the guy said it was fine. I told him of what was going on and he said that he thinks my idle adjuster is out of alignment and that I just needed to realign it. He said that it happens a lot to Mitsubishi cars and that he worked on a lot of Eclipses and Talons and that's what happened.
It's possible I guess but just doesn't make sense. I mean, if my idle adjuster was out of alignment then it should always idle at a constant RPM, right? If it was low it'll always be low and if it was high it'll always be high. My idle jumps back and forth all the time randomly so I don't think that is the problem...what do you guys think?

2-I took my car to Kragen to get a second opinion and the guy tested my battery, alternator, and starter. He said all was fine but my voltage during startup was a bit low but it was fine. I told him of the symptoms and he said to replace the fuel filter and air filter to begin with. Air filter was just replaced about a year and a half ago so I don't think that's the problem. Fuel filter I remember has been mentioned by a couple people here so maybe?

3-I was talking to this guy who knows a bit about cars and told him my symptoms and he said that he had a similar thing happen to his Eclipse. He said that the shop he took it to replaced his air manifold gasket. I don't know if that has anything to do with it but yeah...just thought I'd throw it out there....

So here we are back to square 1. Both battery and alternator are fine. Exterior of IAC has been cleaned but still the same symptoms. :( What to do next? I need help guys...any guidance will be appreciated. I really don't want to have to take it to a shop but if I have to, I guess I'll have to. I'll wait for you guys' help first though....stressing...no good... :(

Air and fuel filter...no don't think so. The AC wouldn't have any correlation to those. If the battery and alternator are fine, I'd really lean towards the IAC, I'd really recommend getting it open somehow and cleaning it, or replacing it. You should be able to find one on ebay for around $50. I'm 90% sure that will fix the problem.

+1 on the IAC. all that trouble you reported in ur 2nd and 3rd posts seemed to do nothing whatsoever. you tested all that stuff from your 1st post. it wouldn't benefit you to do the same thing again, however, i know when you're frustrated its hard to think clearly and be productive, especially in the summer heat.

i can't imagine how hard it is to remove and disassemble the IAC. IAC (http://stealth316.com/2-isc-iac.htm) motor as described by Jeff Lucius is very simple, though his description may be detailed and lengthy. obviously, if the screws wont budge, try some rust penetrant. still no luck, i'm sure you have a friend that has a vise (or you could use this as an opportunity to get a vise!). the total disassembly, clean, test, and reassembly shouldn't take more than 1 hr. there just aren't that many parts.

slade781 these problems have happened to my 94 mitsu. twice already and both times it was the alternator

slade781 these problems have happened to my 94 mitsu. twice already and both times it was the alternator

Hmm...interesting...I already had my alternator checked so I don't think that's the problem...

Well, turns out that my sister's bf does have a vise so I'll be heading there after work to use it.

Stealthee also mentioned that the pintle is supposed to spin (not sure if it's the metal part or the plastic piece) but mine didn't budge when I tried to turn it. I was also doing some research and found this one site where this guy describes that the pintle is supposed to go up and down smoothly when you turn the car to on without starting it but mine only goes up and down the first time. It wasn't smooth though... After I use the vise I'm gonna head on over to Sears to pick up a multi-meter too so I'll run Lucius' test.

Either way, since a lot of you are pointing to the IAC, I'll be getting a different one. Vert's 90% is a pretty darn good coupled with Stealthee and Linebckr's opinion on the matter. I'll keep you guys updated...thanks again for all the help guys. I really appreciate it...

Okay, so my part came in today and I installed it. Started her up and the idle was a bit low compared to usual at about 1000 (on initial start ups it usually idles about 1200). So I let her warm up for about 10 minutes and by this time, it is idling about 700. I turn on the AC and it goes up a bit to 800--then it seems as if the ECU kicks in and brings it up to 900. When I turn on the second option for AC the idle shoots up to about 950. But when I turn it off, it goes back down to about 500. It doesn't drop to 100 and then come back up to 500 but it is automatically idling at 500. Tried it 2 more times and the same symptons came up. I haven't tried taking it for a test drive yet but so far, that's what I have.

So what do you guys think? Do I just have to turn up the idle (BISS-black cap, right?)? Or do you think the problem is still lingering somewhere... Because I'm pessimistic, I'm thinking the problem is still out there. :( If it is, that was $150 down the drain.

Anyways, let me know what you guys think. This sucks man...I really need my car up and running soon....

if you have a known good battery out of something else and swap it and then see what happens i have seen this before and after the zone said it was good

if you have a known good battery out of something else and swap it and then see what happens i have seen this before and after the zone said it was good


I thought certain cars took only certain batteries? Can I use a different car's battery on my car? :uhoh:

Well, I took my car out for a test drive and have the same symptoms. My car didn't die but the idle fel really low and was about to die a couple times. :( Damn this sucks....what could it be? The ECU??? :shakehead

Oh, and I changed both the O-ring and the IAC.

so you ended up buying a Used IAC instead of cleaning your's? i thought you were gonna use ur buddy's vise to disassemble adn clean the IAC, then test with the multi-meter?

after what has happened, may i suggest again: disassemble and clean the IAC, test it. it could be perfectly plausible that you purchased a USED (at least i think it was used, you didn't say one way or the other) IAC, and it needs to be cleaned.

Linebckr49, I bought a brand new one so it's not the IAC. And yes, I did open my old IAC: opened it, cleaned it, put everything back together again. Ran the test and got: 1-2: 30.6 2-3: 30.6 4-5: 32.1 5-6: 30.9 (turns out that my dad did have a multi-meter....he just didn't know what it was called). Still, same thing. I guess I should have posted that one night when I got back but I just figured that you guys didn't want to read about the same tests that I did before so I didn't. At any rate....any other thoughts? Please!?! :(

Oh yeah, and I pulled off the ECU tonight to check for leaking caps but everything looked okay.

many cars have the same group size battery or as long as its close and terminal are the same it will work for testing purposes

So, if you don't turn the AC on at all, it holds a steady warm idle at ~700?

So, if you don't turn the AC on at all, it holds a steady warm idle at ~700?


Unfortunately not. If that was the case then I'd just keep my AC off as I hardly use it anyways.

I was wondering.....when people mention testing for boost leaks, is that only for GTs with turbo engines or can N/As have boost leakst too? I mean....do you pressure test an N/A engine? Because I always thought that was for turbos only when people talked about boost leaks...

That same crap happend to me a few years ago. I messed with the IAC and cleaned the throttle body, resset the computer a zillion times! nothing worked. I took it to the dealer and they did a reflash on the ECU, set me back 350 bucks but never bothered me again. oh and they didnt replace anything on the car, just reflash.

Reflash? The hell is that??? And damn bro, where ya been? LOL Too busy on the GTO forum that you can't come back over here??? :p Just giving you a hard time man....but seriously, what's a reflash? And would you happen to know the boost leak questions I asked?

Our cars cant boost leak but yes they can have compression leaks and if the head gasket, intake manifold gasket, header gasket is worn then it will leak air, HOWEVER, those types of air leak will not cause the trouble you are having.
The reflash is to wipe the ECU clean and set it back to total zero. in other words it like reformatting a computer. Since the ECU tends to learn certain parrameters its not uncommon for it to learn a bad parrameter and then not override it, as a ressult comflicting codes will cause these little headaches.
Apparently just pulling the battery terminals or pulling the ecu out wont completely reset the computer on these cars.
Mitsubishi has a comp. they plug into the diagnistic port and reflashes everything, gets rid of all the codes and set the parameters back to stock.
My symptoms where a bit more extreme then yours though, It started out just like your car but then it simply would not hold idle. If you stopped at a red light it would drop all the way and die. I had to hold the revs manually with my right foot on the gas and brake with the left foot.
Good thing my dad is an ex rally driver and taught me left-foot-brake techniques :icon16:
I almost crashed it a few times but i got the hang of it.

I cant go to the GTO forums! they hate the new GTOs, all they care about are the 70s models.....bastards!

so yeah I come around here once in a while.

Ah I see. But damn, $350??? I need to rule out every other possibility before I go and get that done. Any other ideas? I'm beginning to hate my damn car man....wtf is the point of having it if you can't even drive it???

your just pissed cause you cant fix it! :grinno:

What do you expect from high maintenance Japanese sports cars of the 90's?

I say do rule out every other possibility but you jumped the gun on getting that new IAC, should of cleaned it first man. I hope you dont have to take it to the dealer though. I dont trust them but in my case I was dessperate.

UPDATE: Here's something weird...my car began to hold idle today after I fumbled around with it a bit more. I took off the new IAC I got to check the resistance between the coils to make sure they were good. After that, my car eventually just started to hold at a low idle after having it on for a bit--around 500-550. So I turned the BISS to about 800 and that's where it stands now so I'm thinking that it might be okay. I do have a couple questions though:

1-is it normal to have to adjust the BISS after you install a new IAC to get your idle back to where it's supposed to be? I mean, if the IAC was the same then I don't understand why the BISS would need be adjusted?

2-I don't understand why after I put in the new one my idle was still so sporadic? I must admit that my car didn't die this time but the idle was still very sporadic. I know it takes some time for the ECU to relearn everything but I had my car on for at least 30 minutes and it was still idling crazingly.

3-after I turned the BISS, whenever I gassed my car it seemed as if I would have more power in the pedal now. Umm...is that normal? Is my gas mileage going to suffer because of that?

Well, I'll be driving to work this coming week so I'll let you guys know how it goes. And of course if I'm having problems again then I'll be back. :) Thanks to all who helpped with this problem. I really appreciate it so much...and a special thanks to Stealthee as I am constantly picking at his brain through AIM. Thanks bro. :)

i've never heard of flashing the ECU. sounds like it should work. not that it will solve your problem, but it seems there's a high probability that it would. i guess if you replace a bunch of parts, you could have the ECU flashed as a last-ditch-effort.

anyways, i would just call around to different dealerships and ask them how much it would be to flash your ECU. i bet differen't dealerships charge differently. i know that when i buy parts from mitsu, they are never the same prices at different dealerships.

so that would be your best bet, now that Musashi has enlightened all of us, as he tends to do quite often ;). i don't think they'd charge $350 for it, unless it takes 5 hours to do. basically, when they do a computer diagnosis, all they charge you is labor time to hook it up to the computer. generally, to hook it up to their computer to check a CEL, they'll charge you the going labor rate of 1 hr (usually 60-75 bucks), b/c they just hook it up to the computer, then they are done with it. so unless they have to hook it up to the computer for 5 hrs to flash it, i don't think it would (or they SHOULDN'T) charge $350.

Hmm, interesting

1) possibly, I'm not sure, but it's possible

2) ECUs take at least 15 minutes to relearn, sometimes more, so a half hour, isn't unbelievable

3) Don't think you have more power, it might just feel that way. If you are idling a bit high, you will use a tad more gas, not much. Normal idle is around 700, so 800 isn't too bad.