Base Idle at 0 mph

[PhoenixRPR]

Alright. A week ago I was coasting in neutral and the car dropped to 0mph right away. It would idle fine but it refused to maintain an idle under load. I reset the computer and that solved the problem perfectly. But yesterday my car had the same exact problem, but this time it couldn't even maintain an idle. It would crank, but never kick over. I brought the car (92 GSX) to my local Mitsubishi dealer (the master tech there is a good/smart guy). He said that for some reason the base idle was showing up as 0mph, so he reset all the values as if I had just replaced the Idle Speed Controller (ISC). In fact, 8 months ago I had crebotech send me a rebuilt ISC. After he reset the values, the car idled perfectly. My fear is in a few days I'll get the same problem again, thoughts?

 

[leet]

WAit a few days and if it comes back, let us know.

 

[PhoenixRPR]

Well, it's been 3-4 days and the idle hasn't died on me, but its idling at about a grand and then shooting down to 650ish when the a/c is on. On the way to work today, the car began to have idle surge (AGAIN!). Crebotech sent me a rebuilt ISC like 6 months ago, what the hell? They won't warranty the ISC beyond 30 days. Nooooo...

 

[Fryguy]

The fact that your idle shoots down that much when turning on AC leads me to think that maybe your alternator is failing. Dunno how/if it could be related to the problem, but autozone will check it for you for free.

Just a thought.

 

[PhoenixRPR]

Thanks, but its not the alternator. Doesn't this all sound like my ISC is shot? And if so, where do you suggest I get another one. I got a rebuitl one from crebotech, but it only last for a few months apparently.

 

[nhsean69]

My 2g has always dropped exactly 100rpm +/- 5, when i turn the AC on, my base idle fluctuates from 725-750 with the AC off and the car in park. 2g base RPM is 750 +/- 100

 

[PhoenixRPR]

Right. I'm just reading what the actual specs are according to the service manual. 750 base idle and it should IDLE UP to 850 with a/c on. After I replaced my ISC several months back, it did that perfectly. But ocne again I'm in a tough situation with idle surge. Where should I look for an ISC?

 

[95allorfront]

I have a similar problem i think when the car is idling it will idle at about 7 or 800 and then it will drop down like instanly too 4 or 500 and it will sound like its dying then go back up to 800 or so and someone mentioned alternator before and i didnt know if maybe my alternator could be failing and that would cause the funky idling. Any help would be greatly appreciated thank you very much.
Brandon

P>S> its a 91 tsi if that means anything

 

[talon7684]

Mine idles at like 750 normally and drops to 700-650 with the AC on. I think it was in the manual, but I read somewhere that the A/Ts drop when the AC goes on.