TheExaminer

Sometimes at startup the car will idle really low, then die if I don't give it gas. Once it's warmed up its fine, and will start fine. I've noticed its a little worse since the weather turned colder. I thought it might be the IAC, so I pulled it today and it was pretty dirty. Cleaned it up and the car fires up fine, but time will tell if that was what the problem was because this issue is so hit and miss. My questions are: When I had the valve out, I was not able to depress the pintle at all, not by pushing it down or by rotating and pushing. Does that mean it's bad? If it's fully set and won't move that might explain things. (Btw, it measured 1 1/8" from tip to thread base.) I did an ohm test on the A/B terminals and got 5 something ohms. I put a hair dryer on the pintle for a few seconds and it dropped to 3 something. Seems a little low to me. Next, what should the ohm and voltage readings be at the connector?

dixie wrecked

iTrader: (6)

Assuming you aren't tripping any codes, what engine is it? MAF, speed density or carb?

TheExaminer

Map, speed density. 92 L98..... No engine codes right now other than a pesky 32--but that's another long story. Fuel mileage is only at about 16ish. I'm going to do spark plug/wires/cap/rotor change probably next spring. It does that silly low idle/die thing at startup, and seems to suck a lot more gas on mornings where it's doing that for some reason. This summer it would do it once every couple weeks, but since it's turned off colder it's been doing it more. The IAC was pretty dirty, whether or not that's what's causing it, well, who knows. Couldn't hurt to clean it up though, and it did fire right up after I got it clean. It just bothered me that the pintle could not be moved. One thing I love about an L98 is that they almost start up like electric motors when they're running right. It just fires up almost without turning over at all. But we'll see what happens in coming days. If it still does it I either need a new iac, or that wasn't the problem. I changed all the vacuum lines to the cruise too, they were in bad shape to the point where the cruise would not work. I'm sure that vacuum loss wasn't helping matters.

no new tires

You can't move them by hand, so -that- is fine.

dixie wrecked

iTrader: (6)

Cleaning it never hurts, I agree. I don't think the pintle is supposed to be removable (could be wrong, but mine didn't come out either). I have/had similar symptoms as well. Cleaned my IAC, replaced the burn off and MAF relays and it got better, though it will still start surging/trying to die if I sit still in gear too long.

Have you calibrated your TPS and set your throttle speed?
That helped mine too, though I'm too lazy to set my throttle speed and just 2 foot it when it tries to die.

https://www.thirdgen.org/forums/tech...ml#post1304610

There a a guide on how to do all that

TheExaminer

Ok, I'll check it out. My concern was not so much that you can't remove the pintle, but that I couldn't move it in and out. But the above poster says you can't move them by hand, so I guess that's fine. I was confused because the Haynes manual says to turn it clockwise and depress it. Maybe I read wrong. The PO has messed with the idle screw because the plug has been removed. I've never done anything to it. When it's firing up properly it idles in the 800-1000 range, and I've seen it as high as 1100. When it starts this low idle crap it stumbles down around 4-600 for no apparent reason, and dies if I don't give it gas. I've never done anything with the TPS either. I'd bet the IAC and TPS are OE. I'm pretty new to most of this, so I have to learn as I go. Thx.

TheExaminer

The tech thread says 400 in drive. With the engine at cold start, I'm at 800 in drive and 1000 in neutral, but of course this is with the dashboard tach, I have no other. I may need to try to idle it down, but am not sure if that is related to the other issue. Wonder why the PO did that? Same reason he had the drivers side door moved back and down 1/8" for no apparent reason. Who knows.

Reid Fleming

iTrader: (2)

In terms of 400 RPM in drive......That's with the IAC valve fully closed off (electrical connector unplugged). Once you plug it in, it should resume keeping idle anywhere from 650 RPM (warmed up) to 800 RPM (cold) to 1000 (cold start)

I don't worry about measuring the distance of the IAC valve. I simply take it apart. Clean the pintle, clean the spring, clean the IAC inners, clean the throttle body passage ways and front/back of butterfly valve in the throttle body.

Re-connect the spring and pintle back into the IAC and screw it closed "gently" until it's snug. That way you should have no problem screwing the IAC back into the throttle body.


Setting the minimum idle screw doesn't have to be exactly precise. There is a fairly large window for it to operate. As long as the IAC counts have a window to adjust, it should be fine. IAC counts at 0 = fully closed bypass. IAC counts at 160 = fully open bypass. So it really doesn't matter if the IAC counts are reading 30 at idle or 40 at idle or 70 at idle. Because it can go up or down towards 0 or 160 depending on what the situation is (cold start, hot start, cold day, summer day etc)........To read the IAC counts you need a laptop and an ALDL cable. But following the tech thread about setting min idle and RPM guidelines will work without the use of a laptop and cable.

Reid Fleming

iTrader: (2)

I will also add that it's a lot easier to set the min idle with the RPM at 400 RPM when the car is hot. A cold engine just doesn't want to idle that low ever. This means you'd be cleaning the IAC and throttle body, reconnecting it, and then driving it around for awhile until it's up to temp.......At that point you would do the tech article part about key on but not starting with the ALDL terminal, waiting and then disconnecting the electrical plug on the IAC. This gives you the fully closed IAC valve position upon which to then try and get the RPM at 400-450 RPM (adjust the min idle screw).

Reconnect the electrical connector and you're good to go. Adjust the TPS last as it will change it's voltage when you adjust the min idle screw.

TheExaminer

Ok. Thx Reid! Interesting though. I drove it today and noticed that it idles at 650 in drive when warm--so with what you just posted that looks about right. I'll leave that part of it alone for now. When I cleaned the IAC, I didn't take it apart, only sprayed it liberally with electronics cleaner. I'll look at taking it apart--carefully. LOL......