Pontiac Repair: My 95 grand am isnt working., fuel pressure regulator, engine seams

Question
QUESTION: My grand am for a while at around 55 mph seemed to stutter when just gradually accelerating, but if u stepped on the gas it would run fine. About 2 weeks ago it stalled out on me after a 40 drive and since then has been restarted, but when it starts its very loud, the engine jumps around a lot, and the exhaust is black. My uncle who is a mechanic said the engine seams to be starved for fuel so we replaced the fuel pump but it did nothing, the car has a 3100 V6 and just hit 100K miles. Is it possibly the injectors?

ANSWER: Hi Joshua:

Well first off if it's billowing black smoke it's running to rich not starving for fuel. It could be a fuel pressure regulator that is leaking fuel into the engine. You could have an injector that's sticking open and adding too much fuel. It could be a bad engine control sensor telling the engine to run richer than it should. If there is no service engine soon lmap that has come on it makes it hard to find the issue. Your going to have to take this to somewhere where they have a scan tool to see what is going on with the fuel mixture when it's running to see what the possable cause could be. Good luck :)


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QUESTION: Some added information, it backfires through the intake manifold, my dad said after he replaced the fuel pump he didn't notice anymore black smoke out the exhaust. It was running for a little bit ,then it would stall out, recently we haven't been able to start it. We tried replacing the spark plugs but since then it hasn't started.

Answer
Hey Joshua:

Well if it's back firing through the intake I would tend to look at a spark issue. Either a coild that's acting up or an ignition module. if it's backfiring through the echaust the timing is off It could be even a crank shaft sensor that's acting up. The trigger for the ignition system is the crank sensor that starts the whole ball rolling so to speak. If you have an Ohm meter check the resiatnace of the crank sesnor at the ignition module. It's the smaller connector on the drivers side of the module the wires are yellow and purple. check the resistance. it should be between say 800-1400 ohms it much lower or much higher than that either the wiring to the sensor is bad or the sensor it's self is bad.