''95 GMC K1500 short bed, with 350 '96 vortec, Holly 502-9 TBI , 4L60E,have issue with rich idle and other problems

Asked by May 05, 2017 at 07:03 PM about the GMC C/K 1500 Series

Question type: Maintenance & Repair

check engine light code thrown is low voltage TPS. run down the road  CEL
pops on , engine increases 300 rpm.. from start it shifts at higher rpm and
speed and rough shifts. shut off and restart...all is good again except for
high idle and rich exhaust. Have had rich exhaust at idle since change out of
engine. Had" Motovation" provide a chip for the computer as original engine
was a 305. new engine is a production L31  350 v8 Gen 1e for 1996-2002
HD truck. GM performance parts intake manifold #12496821 and Holly 502-
9 TBI. what do you think is trouble(s)???

3 Answers

115,915

Are you still using original throttle position sensor? If so check wiring, tps itself and proper settings of the sensor.

original TPS is in use, "proper" settings? what are they and how to adjust same, would be helpful to this old salt. I have ordered a new TPS from Holly for this unit. ten(10) day wait for delivery. I want to check fuel pressure too. But lack gauge to do so and where to check. I am a retired electrician and have already checked wiring. thanks for your input!-Mike

115,915

Ok most tps range from .5 to 1 volt at closed position and 4.5 to five volts at wide open throttle. Some also have others functions as well. But if yours is a three wire one then with key in on position you should be able to read 5 constant volts on one of the wires this is the supply. One wire is a ground and the other is a signal. The signal wire is the one to test. It should start at .5 to 1 volt closed throttle and as you move the throttle it should smoothly increase to around 5 volts. Voltage should smoothly climb and decline as throttle is moved. If it jumps around or reads extremely low or high then position sensor is probably bad. Now this is just the generic way these things work might not be same as yours but I am almost positive it is.

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