Hey guys,

I believe I had this problem last summer too. It only seems to happen when the temperature begins to get warmer. What will happen is I'll turn my car on, and whether I go instantly, or wait 5 minutes, when I shift into drive, the car'* power will seem to die down and everything... the RPM'* will go under 500 most of the time, the lights will dim, and then it will kick back up and be fine.

Sometimes though when it does that, it will stall out. I'll throw it into park, it'll turn right back on, and then I'll be fine to go.

What would cause this? I changed the oil not too long ago at all, so what else could it be? I believe this only happens during warmer weather.

does it happen before or after you hit drive?

Alright, I have heard of this issue before, but I could be wrong on a few of my facts.

When the tranny engages [normal conditions], the engine will drop one to three hundred RPM. Then, a second later, go back to normal idle. Unfortunately, as our cars ages increases, so do their reaction times. This process slows, and the car takes longer to react. Now, along with this, our transmissions age, and begin to give us a little trouble. This causes extra load on the engine, thus causing the RPM drop, and sometimes stalling.

All-in-all, this is a transmission issue, but the ECU can correct it.. [this is where I am unsure of my facts; somebody please correct me if I am wrong]. There isn't much you can do. But there is a little. I remember my RPM dip decreased when I cleaned my intake up, including my IAC [Idle Air Controller]. My car would do the whole stalling whatnot occasionally, but it'* been a while. And mine was only in Reverse [my tranny has some issues with it'* reverse gears, IMO]. Clean up your intake, and you should see some improvements. If not, just live with it. Nothing serious, just age.


-justin

Agreed...

I really don't see how this could be a transmission issue at all. When you shift into drive at a dead stop, with your foot on the brakes, the transmission itself isn't really doing anything at all (aside from shifting, obviously). What I mean to say, is that the torque converter is just slipping at this point, and the transmission isn't doing much of anything after the initial shift action, until you let off the brakes and give it some gas, and then things start to turn and the car moves. So no, I don't think an elderly transmission is the issue here, unless the torque converter is somehow binding up somewhere or the lockup clutch is remaining partially engaged (and I suspect that stalling out would be the least of your problems in this case).

The reason that the engine RPM drops when the car is put into gear is simple. The engine goes from running under virtually no load to being under some load due to the transmission going in to gear and forcing the torque converter to slip, causing resistance there. In order to continue running, the engine needs more air. This need is supplied by the IAC (Idle Air Control valve). After years and miles add up, this IAC can get gunked up to the point of being sticky or sluggish.

So that'* what I would try first - pull the IAC and clean it up good.

I concur. First thing I thought of, as well. Your engine relies on the IAC to keep it up to speed at idle. If this is faulty, it does exactly what you described. Plus, they're prone to failure. I've known of a LOT of GMs with this issue.

Alrighty... I'm not "mechanically challenged". I'm able to take things apart and put them together as long as their not too difficult.

Where is this IAC, is it easy to access, clean, and put back into place? If so then I can do it.

******' A, I swore I edited that. I didn't mean a transmission problem, I meant intake problem. Clean the IAC and TB, that should fix you right up. Sorry about the confusion.

The IAC is under, and just to the right of the TB. Has two phillips head screws, with a connector going to it. Just pull it out, and make it shine [doesn't take a lot of work, but gives good end results].


-justin

Clean the MAF while your in there also.

TB? Pictures of the IAC or MAF, detailed pictures if you don't mind, and what do I clean it with?

Throttle body is here on the engine



Heres a diagram



It is held on by two phillips screws...make sure you don't lose them, because it is easy. Use some throttle body cleaner. Spray it until the black crap is all gone and the drip is clean. Then make some sort of pipe-cleaner type thing and clean out the housing it was in as well. Reinstall when the valve is dry. I don't have any detailed pics right now, but I may be able to get some later.