Help with Grand Prix problem!!

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Old 06-01-07, 06:52 PM
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Question Help with Grand Prix problem!!

I recently bought a 1991 Pontiac Grand Prix w/ 3.1 engine as a project(price was cheap). Engine starts up immediatly when cold, and idles in park just fine and runs good while still cold. Problems are: when it warms up, it runs poorly, seems to be choking for fuel, and will start to die and eventually die when coming to a stop or decelerating. It will restart ok 10 - 20 times, but when it does, it does not idle properly, it almost dies, then idles back up and lopes a little. This is the scenario for a while, then it won't start back up....just turns over, but won't fire. The next day when engine is cold again, it restarts like new..as if nothing wrong, but will repeat the above description over and over again. I won't leave the property with this car because of this problem, and have already had it towed back once. Any help would be greatly appreciated
 
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Old 06-01-07, 07:14 PM
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Couple of things.

1. When it is in the no-start condition, have you checked for spark? Need to narrow it down to spark or fuel, but I would lean toward a spark problem.

2. Read codes:

http://www.troublecodes.net/GM/

3. Using any coolant? I.E. does the coolant level remain constant or are you having to add water/coolant?

4. Wouldn't hurt to change the fuel filter.

There'll be others chiming in with questions and suggestions, but these will give everybody some basic info.
 
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Old 07-02-07, 10:18 AM
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Same problem

I have the same problem with my 1991 grand prix, except now things get worse and now it turns over, but won't run. There are no codes flashing, I have changed the fuel filter, fuel is getting to the injectors, changed the idle air sensor, installed new ignition coil and even replaced the computer. Still won't run. Have you had any sucess with yours?
 
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Old 07-02-07, 03:04 PM
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There are so many things. So many sensors and stuff. You say you have gas to the injectors, but there still is issue of exact pressure and volume.

But lets say you have no gas issue.

Check for spark.

Check engine with timing light test to make sure you are getting fire at correct time to cylinders to rule out other stuff.

Does your engine have a distributor/rotor you can check orientation and spinning of, when cranking?
 
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Old 07-02-07, 03:25 PM
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If it were me I would change the fuel pressure regulator in the rail.
 
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Old 07-02-07, 07:35 PM
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arson; what size engine and what did it do prior to not starting, if anything.

Does it crank well now? Does it crank "different" than normal?
 
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Old 07-03-07, 03:25 PM
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It is a 3.1L engine. Last October the wires, plugs and coil were replaced. It ran from Chicago to Southern Illinois just about every week. The only thing then was if it was turned off after the trip, it may crank but not run. Then eventually it would be running then stop. It would crank over, but not run for about ten minutes. There was a trouble code for the idle air sensor and that was replaced. I also changed the fuel filter. There is spark, put when the valve on the fuel rail is depressed, some gas comes out, but not like if it is under pressure. Then it started a slow death. It would start and run, but when the engine warmed up, it stopped. Now it cranks, but will not start. I also changed out the computer and checked the fuel pump...which is working.
 
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Old 07-03-07, 07:55 PM
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you say the fuel pump is working.

Is it working well enough? Have you taken a volume or pressure reading?

low pressure could be two things basically; fuel pump and pressure regulator.
 
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Old 07-09-07, 02:39 PM
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So there was alittle pressure at the fuel rail before I replaced it. When I did replace the fuel pressure regulator, I noticed the gaskets for the plenum appeared to be leaking, which was probably contributing to the problem. Now after everything is put back together, there is no fuel going to the fuel rail. I tested the fuel pump with the test lead that is located by the fuse/relay in the engine compartment. I cannot hear it run, but with a volt meter I know that there is power getting to it. The question is, can I test the fuel pump after I drop the gas tank and take it out? Does it seem like that this is the problem, no fuel, no humming of the fuel pump...
 
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Old 07-09-07, 02:49 PM
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just so you don;t feel bad, I replaced the fuel pump twice on my daughters 91 GP. Acctually I had it done, I hate pulling tanks. I had it to the garage for no fuel pump run 3 times though. The connections at the tank were a problem for some reason.



The other thing that was replaced was a couple of connecting hoses that connect from the body to the tank. Can;t remember why but I trust the folks that own the garage and they said do it so I said do it.

Yes, you can test the pump when you remove it from the tank but don't run it for any length of time. The fuel actually acts as a coolant and a lube for the pump and without the pump being in fuel, it will smoke the pump pretty quick.
 
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Old 07-09-07, 03:49 PM
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I had a similar problem with a Buick with the 3.1 and it was a connector that went to the transmission. The connector was removed and the car has run fine since. I'm sure others here can clue you in better about the connector but I remember it was a three letter name.
 
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