Stalling when accelerating Help!!!

[TazMan]

Hello all. I'm new to the forum and I'd first like to say what a great site you have here. I've learned more from this forum than I ever thought I could know. Now my problem is I have a 1992 Pontiac Grand Prix that stalls almost every time I try to accelerate. It doesn't do it every time, but most of the time. I've found that USUALLY if I stomp down on the pedal when this happens before the car actually turns off, the car will take off and be fine till the next time I try to move from a complete stop. It's great on the highway, but is very annoying in traffic! Now I should mention this car belonged to a mechanic, the mechanic put new plugs, wires, and whatever else it needed to run well for a friend he was giving it to, then when the friend got it, she couldn't insure it so it sat for over 9 months in a driveway until I got it. Also it wasn't doing this from day 1. It started about a week after I got the car. But it seems to me to be slowly getting worse. I took out a couple of plugs to see if he really changed them and they look brand new out of the box. So do the wires. I also replaced the gas filter the first day I got it. Any ideas would be greatly appreciated. Also I have some questions about a 3100 top end from a 95 buick century that I am gonna attempt to swap onto this 3.1 if I ever get it working right. Should I post them in pushrod performance or engine swap? Thanx everyone for reading.

[SappySE107]

Pushrod performance. There are better options but if you have the 95 manifolds and don't want to get another set that will still be an upgrade over stock. Tuning required.

If you drive it slow on take off does it still stall? There are quite a few possibilities that I can think of but I can't say I know if any are even right. Do all the plugs look the same?

If you had a scanner you could see what the computer is doing. Do you have a laptop? The software is free and the cable is $80 from moates.net. Others have made cables as well so you can look around. Thats just the one I use and I like it (USB).

[TazMan]

Well when it first started happening I noticed if I accelerated VERY lightly it would be alright but thats not so much the case anymore. I actually was just driving a little while ago and it was driving fine for a long time and then it started acting up again. There doesn't seem to be any kind of pattern as to when it happens. Sometime it's always doing it, and sometimes not. It started out as just an occasional thing and now it's almost all the time. I also noticed that when it's acting up it seems to be worse under no load. In other words, when I am pulling away from a stop sometimes it's not that bad, but if I am sitting in park and I hit the gas it almost always just bogs down and will stall unless I let off or stomp it to the floor. When I stomp the pedal it will roar really strong like nothing is wrong. Also earlier today when this happened and I stomped the gas and it just wouldn't go. I was going up a small hill, I had the pedal to the floor and it was just slowing down. When I got to the top of the hill I released the gas, stopped at a stop sign and when I continued again everything was fine. It never even stalled this time, it just wouldn't go up the hill. I did have the pedal to the floor the whole time cause I was hoping not to stall in front of the line of cars that were behind me honking. This is the first time that happened. I didn't check all the plugs, just the front three and they all looked VERY new but the same. I will check the other plugs tomorrow. I do have a laptop, only 700MHz but if that is not fast enough getting my hands on one for a little while would be no problem. I am working with VERY little cash so I am gonna have to do some searching on how to make this cable. I'm a computer tech and have parts and USB plugs lying around so that shouldn't be to much of a problem. I also forgot to mention if the map sensor is disconnected and the vaccum to it from the manifold is plugged up, it doesn't do this at all when it is parked. I didn't want to try to drive it like this, just tried it in park. Also the car eats ALOT of gas but I assumed that was from me mashing the gas pedal to keep from stalling all the time. As far as the 3100 top end swap goes, I know there are better heads, intake, etc. I can use from newer 3X00 motors but I am working on almost no budget and I have most of the parts I need in the buick already. Im not looking to race, I was just hoping to breath a little more life into this slow dog. A company called Standard Abrasives makes a DIY head porting kit, http://www.sa-motorsports.com/diyport.shtm, that can be had on ebay for about 60 bucks with shipping. I was considering picking this up and attempting to use it on the 3100 top end before putting the parts into the Grand Prix but I don't want to do anything till I get to the bottom of whats wrong with this car. Anyway thanx for reading and thanx so much for the quick reply.

[TazMan]

Is this really an accurate test?

Okay so after doing some searching I now know that making a scanner cable for the laptop is a bit more involved than just splicing some wires. I did however find a post that said if you short pins A&B in the scan tool port with the key off and then turned the key on without running the engine, the "Check Engine" light will flash with the codes. Well I tried it and sure enough it worked. I got codes 22 (Throttle Position Sensor), 23 (Manifold Air Sensor), 33 (MAP sensor Vacuum or ECM Electrical Connector), and 34 (ECM sets a fixed MAP value and uses TPS to control fuel delivery). Now my question is, is this an accurate test? Are the computer codes usually checked WITHOUT the car running and if so is this an accurate way of testing the MAP sensor since there is no vacuum with the engine off?

[SappySE107]

Thats an accurate test to see what codes are stored in the computer. Seems like you have quite a few things to fix and it also explains the bogging. Its using the TPS for fuel because your MAP is screwed or the wiring to it or the vacuum line that its connected to.

check the TPS, MAP, and IAT.

[greekguy7]

Two things come to mind:

1. Check your fuel pressure with a gauge; should be about 40psi.

2. If your pressure is fine, then you will need to meaure your fuel injectors with a multimeter. They should be at least 12ohms each. I had a similar problem with mine. I found 3 injectors below spec. I changed all 3 and happy ever since.

[TazMan]

Just a quick post for anyone else having similar problems. The stalling is fixed. You can read about it here http://60degreev6.com/showthread.php?t=33879. Thanks everyone for all your help and all the info I learned along the way.