Engine stalls under load at times. Service Engine Now light goes on.

FNIESTEM

MEMBER
1995 PONTIAC GRAND AM
3.1L
V6
2WD
AUTOMATIC
196,000 MILES

Usually (and not all the time) at highway speeds the car starts bucking and eventually stalls. The speedometer goes crazy just prior. The temperature gauge is at half and the car appears to be not overheating. I pull the car off the road and waited a few minutes and the car starts and drive again as if nothing happened. On a recent long trip from Syracuse NY to Fairfield CT, the first 80 miles when okay. The fuel tank was almost full when I left. As the tank empties it appears that the situation described above starts. Eventually I had to refuel ( and this is all coming out as I write this) and the car ran fine. When I exited 17E to 84E the trouble began. The tank was probably half full. The engine would buck and stall. I waited a few minutes and it’s started again and ran a few miles and it repeated. This happened about 30 times. At on point there is a steep hill and just on the hill it stalled about 8 times. It only ran for a few feet. Eventually I exited on 84E exit 3 to Rural route 7. At a lower speed it only happened twice. And I made it home via Route 1. I only owned the car for two months and in the 1300 miles I put on it I replaced the water pump, timing chain, timing change cover and gasket. There was oil and antifreeze mixing at the timing chain. At another shop they replace the spark plugs at my request and found additionally one bad coil and replaced it. The problem in diagnostic is the they claim they can’t get the data. The port has three prongs on the left side:
(Empty). A
L. M

so can you help?

1 Reply

STEVE W.

MECHANIC
12,996 POSTS

This sounds like a failing fuel pump module. Namely that it is not pulling fuel properly and needs the pressure of a full tank of fuel to operate. Actually a common thing in the older GM vehicles as the pumps age. They crack in the reservoir or the pressure line above it or the pump itself doesn't act properly due to wear. The repair is to replace the pump module.
Repair calls for draining the tank, then removing the tank to get to the pump assembly retainer. Then removing the unit and reversing the process.

This is a guide on it showing a similar system:

https://www.2carpros.com/articles/how-to-replace-an-electric-fuel-pump

As for the data connection, The 1995 Grand Am is one of GMs worst ideas. It is commonly called OBD 1.5 It falls between the older OBD I that could flash the light if shorted and the newer OBD II like more modern cars use. It was only on a few vehicles between 1994 and 1996 when OBD II took over. The problem is that a modern scan tool usually cannot read it unless it's a higher end unit with the correct software, and the older OBD I tools don't work either unless it is one with the correct software as well. Tools that do work on it are the OTC Genisys and the Snap-On MT2500 "brick" You can find those both reasonable on eBay if desired. Or find a shop that has one of them and knows how to use it.

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