1999 GMC Sierra Truck won't excellerate?

JACKINTEHACHAPI2

MEMBER
1999 GMC SIERRA
V8
4WD
AUTOMATIC
140,000 MILES

Seems to be a problem with a rebuilt transmisson. When climbing up a grade the truck won't excellerate. Seems to be in some kind of safe mode and will only go around 20 mph. Eng will not rev up past 2000 rpm?
I replaced the fuel pump, fuel filter, throttle position sensor.

3 Replies

MERLIN2021

MECHANIC
17,250 POSTS

How does it rev when it's in neutral? Does it seem to be a plugged converter? Or is the engine smooth and just not moving? Let me know about the revving in neutral.

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Friday, October 31st, 2008 AT 11:28 AM

JACKINTEHACHAPI2

MEMBER
1 POST

It revs but not like it should, also needed to mention this all starts when the transmission fails to shift then the rpm stay's at 2000 rpm and will not accelerate.
I finally got 2 fault codes to read. One code was (p0131) say's 02 Sensor Circuit Low Volts (Bank 1 Sensor 1) The 2nd code (p0300) say's Random/Mulitple Cylinder Misfire Detected. This truck has four 02 sensors. 1 in front of the converter, and 1 in back on both sides (2 converters). Do you know which sensor is the one noted in the fault code. They cost around $90.00 bucks each.
I was also told the mass air sensor may cause this problem? Is this probable.
I am repleacing the spark plugs, MAP sensor, & PVC valve to see if that helps.
If there is an internal electrical problem in the transmission causing not to shift, would there be a fault code reading?