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Random RPM stumbling/stalling

R

Ransom

New member
Hey guys I've been trying to troubleshoot this problem since March. Car is a 2001 Pontiac Grand Prix GTP with only 71,000 miles.

Here's the problem, back in March one random day while I was driving my engine started studdering and finally stalled while I was giving it gas. It re-started with no problems.

The next day, while driving on the highway, it did this 3 times in 20 minutes, all while cruising at 70mph. Each time, I pull over, turn the car off and back on. Then on the way home it didn't do anything.

I had the crank position sensor replaced. The plugs look fine. Cleaned the MAF with CRC. It's still doing it. Next step will be to unplug the MAF to put it into speed density mode.

Here's what I DO know.

-Car restarts fine everytime
-Totally random, can't reproduce it.
-If Im driving and it starts to studder, the engine will remain stable as long as I don't give it more than ~10% throttle.
-After it starts to studder, when I give it more than ~10% throttle, the engine will stumble worse and then stall. When I give it more than ~10% throttle, my Scanmaster says .000 millivolts for the O2 sensor. I'm 95% sure thats why it stumbles and stalls.


Today 6/26/2009 on the way to work it stalled SIX times within a 3 mile distance. Each time it restarted with no hesitation.
 
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Here is a scan.

2009-3-25-R1 from ransom83 -- Scan Depot dot net

It starts to stumble around cell 340 while slowing down coming to a stop sign before it stalls.


Around cell 955 I was at a stop sign, starting to accelerate and it started to stumble. I took my foot off the gas, let the car coast (5mph), tried giving it gas again at cell 1007 and it stalled.
 
I just had the same probelm with my 04 grand prix I changed the crank sensor, map sensor and the control module still the same probelm so I took it to the dealer and it turned out to be my fuel pump i was suprised becuase it wold start up and run fine later. It runs fine now
 
Yeah thats what the problem was. The shop replaced the fuel pump, fuel filter, and did some sort of decarbonization/cleaning system through the engine and it runs like a champ now.
 
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