Won't hold idle randomly

In the past week my car has done this on two occasions. First time I was leaving work, started up the car, RPM went up and then dropped back to 0 and stalled, it kept doing that until I unhooked the batter for a minute and then it was fine. Second time I was driving, pushed in the clutch to stop at a light and RPM just dropped to 0 and stalled. It kept doing it until I got home, had to hold RPM w/ the heel-toe method to stop. Drove it later that day and it was fine, so it's pretty random. I see a lot of idle questions on here so I was hoping it's common, anyone have any suggestions?

Well the general erratic idle problems are usually unplugged Mas, IAC, vacuum leaks, plugs, possibly o2 sensors. But with it only happening occasionally, and the car stalling, I dunno, I doubt it's the last 3.

THis thread might help:

http://www.3si.org/forum/showthread.php?t=277400

Most likely the IAC on its way out or just gunked up. When my IAC was on its way out it would act up randomly too. I never knew if I was going to idle at 2k rpms or stall at every stop light.

Would the IAC have something to do with the stuttering that I get when I punch the gas from idle? It kind of hesitates, didn't do it 5,000 miles or so ago.

It started doing it a lot more now, so I read through all 11 pages of the link you gave Igovert, and I read the thing on Stealth316 on the ISC/IAC and I feel a bit more educated on idle and surging problems. But i'm not sure if any of that pertains to me because in everyone's case on there, they had problems with surging. My problem is this:

1) Idle's very low, around 100-200 rpm, engine cold or hot.
2) Stall's out after punching throttle up and letting off quickly after.
3) If I ease the rpm down to 100-200 rpm it will hold it there, sometime's will only hold for 10-15 seconds and then die.
4) The only time it doesn't do this is the first 15-20 minutes of driving after disconnecting the battery to clear ECU. After which it starts stalling again.
5) Stuttering when I hit the gas from idle until RPM > 1000-1500, whether in gear or neutral.

So tomarrow since I need to replace my clutch, a few wheel studs, and the noisiest brake pads ever made, I am going to take apart my car. While i'm at it i'll inspect, test, and clean the ISC/IAC as per Stealth316's instructions. So if anyone has anymore thoughts on it I would appreciate the help.

On another note, where can I get a datalogger for my '94 SL?? I see one on Ebay right now for 91-92 but in '93 they changed the plug so I can't get that one. I really need one.

yea clean the ISC/IAC. kinda wierd since it stops when u reset the ecu. and im havin problems with my car bucking in a certain rpm range.. an it seems to go away a bit when reseting the ecu, but it comes back an gets worse.

just take your IAC out, clean it and put it back in, that has helped a lot of people

but yea, it sounts like your IAC might have gotten a little dirty

i got a cleaner from the auto parts store, it worked pretty good. its the stuff used to clean altenators an starters. anything electrical really.

I can almost garantee its the IAC, mine did the exact same thing, cleaning it didnt help much so I ended up getting one off of ebay for 20 bucks and now my car is running like a dream...

hmm I see them on Ebay, I take it mine uses the same IAC as a DSM 4g63?

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1&category=33557&item=7986817662&sspagename=WDVW

good deal or no? What do you think they do to rebuild them?

Ok have to edit this post:

Took out IAC, took it apart, cleaned it. It revs a little smoother now, but it just stalled on me again. For a little while it was good, drove it around for a good half hour, shut it off, turned it back on and it stalled. I measured the resistances of all the coils and they're all within spec. Does this mean it's something else? or can the coils be in spec and the IAC still to blame.

How is it when driving down the road. taking off an such?

Well other than my horrible clutch slipping, its better than it was, now that I cleaned the IAC. It still stutters if I floor it in neutral...RPM's will stutter while going up until I give it less throttle. It doesn't do it in gear though.

I just found out that I may have measured my resistances on the coils wrong, because Stealth316 says to measure terminals 1-2 and 2-3, but I looked it up on Mitchell On Demand at work and it said 1-2 and 1-3...so i'll have to do it again and see how it turns out. I hope all I need is a new IAC, seems like the problem to me, I really want to get this running right so I can sell and get my 97 VR4!! wtf.