Hesitant acceleratrion on long trips. Couple ideas.

[Othermusketeer]

I actually dont have my A-body anymore. I now have an H-body, but I trust the people on here.

The Car
1993 3.8L v6 Pontiac Bonneville SSE, >250k
previous owner said: no engine or tranny work/overhaul, coil pack replaced

The Symptoms
Normally engine runs great, lots of power.
On longer trips (required length getting shorter and shorter) the
car will have acceleration problems when accelerating, but seem fine
while at a constant speed.

When passing 2.5k-3k RPMs the engine will suddenly go quiet and the RPMs drop to 0. Then just as soon as it does that, the RPM return to about 2k and start rising again, only to repeat the cycle. Accelerate, stall, accellerate, stall, accellerate, stall... the entire time I place more than the slightest of pressure to the gas pedal. If I barely apply throttle, I can eventually make it to 45mph from a light with a minimum of hesitations, but it takes a couple minutes of blocking traffic.

If I pull over and put it in neutral, I can bring it up to 5k without any problem. If I turn it off for 20min it will be fine. On one occasion, I was having the problem and stopped to get gas (was at 1/4, so not an empty tank thing). After getting gas the problem went away during that trip.

Thoughts
I've been reading posts here and some google results, and have some ideas.
Spark - Plugs, coils, wires, etc. These seem to cause a problem the whole time, not just on longer trips.
mixture - faulty ECM, bad CAT, bad o2 were sometimes pointed to, but my problem isnt when the engine reaches operating temp. Its when its been running on a trip >30-45min.
fuel pressure regulator - The vacuum hoses are old and I need to replace them, but acceleration on short trips is fine.
fuel pump - At first I dismissed this, especially since neutral seemed to accelerate fine. However, if the pump were slowly going bad, and over heating in the process that would explain what makes the problem go away. Turning off the car for a while, and adding cooler gasoline to the tank.

Dilema
My finances are crap right now. This month I have more in the expenses column than the income column; A LOT MORE. I really dont want to throw parts at this.

Any ideas?

[weroberts]

I'm gonna guess fuel problems. A few things to try:
As you have a 3800 unplug the CAM sensor (next to the water pump) The check engine light will come on, but the computer will then set the fuel pulses off the Crank Sensor instead of the CAM. If this fixes it then your fine.

As a second guess, Pull and Plug the vac line to the fuel pressure regulator. You may run a little rich, but it should be fine. This will leave your fuel pressure at the highest it'll go.

These are 2 free things you could try.

Beyond that have you replaced the Throttle Position Switch?

[Prospeeder]

Possible Bad Ignition control module. Long trip makes it heat up and fail. There not in the crap spot on the block under the exhaust manifold like 60 degree V6's are so they tend to need alot of temp to cause a failure, long trips tend to do that. Seen it a few times.

[Othermusketeer]

Thanks for the responses.

@weroberts: I will have to try those the next time it is acting up.

@prospeeder: I will do some research about symptoms, diagnosis, and costs of ICMs tomorrow.

[Casper]

My ex girlfriend's mom had a Grand Am that did the same exact thing. It turned out to be the fuel pump. It started out only doing it occasionally, then it got to the point it would do it ALL the time.

[weroberts]

Thanks for the responses.

@prospeeder: I will do some research about symptoms, diagnosis, and costs of ICMs tomorrow.

Autozone will check it for free if you take it off and to the counter. They're fairly expensive. If it is a heat issue. Take some Terminal Greece and put it between the back of the ignition module and the Aluminum housing. Theres actually supposed to be some there from the factory.

[Prospeeder]

its true some places can test them, but if they ONLY fail at high temp a bench tester wont recreate that

[85_Ciera_Rebuild]

Accelerate, stall, accellerate, stall, accellerate, stall...


Experiment...when engine is cold...start up, place in Drive, and slam accelerator pedal to the metal...up to 70 mph....like around interstate highway.

If same pattern, your fuel pump is shot, or you need a new fuel filter.