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runs rough at 2300RPM


DRfabulous
09-03-2007, 10:26 PM
I just bought a 2001 S_10 quad cab 4x4 with the 4.3 motor in it. After having it for a few weeks i noticed that is would start to run rough at 2300RPM untill the shift, usualy around 3000. It is kinda of hard to explain the feelign but you can feel it in the floor boards when you hit 2300 or so, the best discription is that it drastically changes from a smooth accelorating motor to a rough one within the 2300 to 3000RPM range. I did a tune up, new plug, wires, cap, rotor (all GM parts) and an injection service, as i was told by the dealer this was my problem and i still have the exact same noise. The tranny fluid is good and wil be flushed soon and i was told by another mechanic the the shifts were good and that t was most likly not a tranny problem. the noice is the same in all gears includign nutral and park, so dont really think we have a tranny problem but who knows. any one have any ideas? This was supposed to be my do nothing truck so i could get through grad school, but i am startign to hate it more and more every day.

taillight
09-04-2007, 08:46 AM
Do you have any trouble codes ? You may have to drive with a scan tool on that will read live data and watch things like the MAF, long and short term fuel trim, O2 sensors to see what is happening.

DRfabulous
09-05-2007, 06:33 PM
i had the dealer run the diognostics on the engine and the tranny and all checked out within specs....i am thinking it has to be something mechanical like a loose torque converter or somethign that is not hooked to a sensor. so no one else has ever had this problem?

82Stang
09-05-2007, 07:31 PM
Maybe:

-coil starting to go bad
-TPS(throttle position sensor)
-weak u-joints
-out of balance driveshaft
-check all underside bolts

Some things to check.

DRfabulous
09-07-2007, 12:54 AM
Well, the GM dealer by me tried to pass it off as just as a typical attribute of the 4.3 motor (typical answer when they cant get to to bottom of a problem). I told them this was bullsh*t, as i have been in several simular and different makes modles and years of the vehicles with this motor and none of them have this noise/vibration. So they went back and contacted the GM headquarters at my request adn troble shot the issue for a day with the big dogs. The solution....a new exaust system. This is based on the conclusion that there is a posible harmonic 'imbalance' so to speak, this is either due to a poorly designed exaust system, being that the motor creates this vibration through the exaust system that has been lengthen for my S-10 quadcab due to the frame length, or that the exaust has already started to break down enough at 60K that there is a slight restriction through the system. The dealership has found it so unusual that they are willing to slap a new exaust on for free to see if it works. I get it next week, i will keep all posted as for future reference if it is ever needed i guess..:banghead:

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