Okay, I have a 1998 Monte Carlo Z34 with the 3.8 liter engine in it. Just to give you some background on the car. I recently had to have the fuel pump assembly replaced. The car has 169xxx on it. It has a 4500 watt stereo system in it that literally drains all my electrical juice when I turn it up. (Needless to say now that Im having this problem I pulled the amp fuse at the battery.) Now there is no extra drain on the charging system. A lot of times, but not all the time, the car will start up just like normal and the run for about 2-3 seconds and then shut right back off as if you turned the key off. When this happens I notice the tachometer doesn't work at all. When it starts up and stays running the tac works just fine. I don't get it Im lost and I don't have the cash to take it in to get it checked out. This is my daily driver and I gotta get back and forth to work. I don't want to get stranded on the side of the road cuz its about 20 below zero here where Im at in Michigan. HELP! Thanks.

 

It might be worth having someone scan it for any codes (even if the CEL is not on, a good scan tool can tell you if a code is pending). Based on your observation about the tach not working when it shuts off, I am guessing there is a sensor problem (I want to say that is controlled by the crank position sensor, but don't quote me). My speculation is that the sensor is not giving the PCM a reading fast enough and that's what's causing it to stall.

But, this is a speculation. See if you can get a good scan tool on it and go from there.

 

Thanks for the info. Ive heard these cars are famous for the crank position sensors. Im gonna have to check it out. Does anyone know how to test one of those without a scanner?

 

I don't know where your at in Michigan...
But you can go to any auto parts store and have them scan it for you for free!
Me personally...
I'm downriver in Taylor... I have 4 different auto parts to choose from.
That have/do free scans.

In my 1999 Z-34 3800 I have never had this problem...
Did you change the fuel filter when you did the fuel pump?
Have you checked the fuel pressure at the fuel rail?
This maybe the cause of the stalling.

At my local auto parts you can also get the fuel line pressure tested.

But as far as the crank sensor...
I don't own a tester... So I would maybe possibly consider getting a crank sensor from the junk yard and swap it out and see if the stalling issue continues..
Just be sure its from another 3800.

But I'm kinda leaning towards a bad/plugged fuel filter...
I'd start there as its also cheaper..

 

This is just an experience that happened with one of the 5th Gen. Montes that I owned and may or may not be the cause of it shutting off.
**Check the Vacuum lines that may not be connected. I am attaching a photo of the area that I found the Vac. line it was larger and was not connected. Just a shot in the dark but might just be the trick. Fuel filter could be the culprit as well. You will find it on the Passenger side under the rear seat foot area on the outside of the car looks like a beer can with an inlet and an outlet, Careful when you try to replace it that you don't twist the fuel lines. Hope this helps.

 

Yes the fuel filter did get replaced. I did that at the same time I replaced the fuel pump assembly. The whole fuel system in the rear of the car was replaced. Also, keep in mind that the tachometer goes crazy when the car is doing this. That's why I am led to believe it is some sensor somewhere. Thanks for all the help everyone

 

Well just so everyone knows. I went to AutoZone and had the car put on a scanner and it was showing low voltage on various sensors. So, I checked out the body ground and sure enough it was loose. I tightened it up and the Tachometer is staying stable and its starting every time. Yay! I cant believe it was something as simple as a stupid loose ground wire.

 

Curt,
Glad its was something simple

Which body Ground?
Got a pic?

You can link/post it thru photo bucket.

 

Awesome, free fix!! Doesn't get better then that!!