1994 1/2 ton 5.7 silverado no balls over 1/4 throttle - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 04-23-2012, 11:15 PM   #1
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Default 1994 1/2 ton 5.7 silverado no balls over 1/4 throttle

ok so im working on a 19941/2ton 4x4 silverado 5.7 v8 tbi OBD1 truck
no one has obd 1 scanner so i havent figured this out.

ok anything above 1/4 throttle and it boggs down terribly n barely moves but wot it tries to go but still dont have enough power to get over 25mph. now when timing is adv to 25* then it gets to 1/2 throttle before bogging n has a bit more get up wot is actually somewhat driveable n can reach speed limits.

does not smell rich constantly.. only smells rich after it stops bogging down.

i replaced the ignition control module, cap, rotor, plugs, wires, throttle body, iac, tps, ign coil, map sensor, coolant temp sensor, o2 sensor no difference.

now if the iac is unplugged it dont stall at idle but when its plugged in i cant idle in gear or turn the wheel at idle or it stalls and has even less power.

also blocked egr incase i was bad with no change.

no service engine light either

it sat for a month or two then it ran like this.. ran 2 full tanks of fuel through it since then with drygas in first tank and seafoam in second

not sure whats left other than pickup coil fuel pump or electrical issue... n doubt its mechanical issue
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Old 04-23-2012, 11:17 PM   #2
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Clogged catalytic convertor?
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Old 04-23-2012, 11:20 PM   #3
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no cat....
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Old 04-23-2012, 11:32 PM   #4
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Injectors?
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Old 04-23-2012, 11:53 PM   #5
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swapped tbi unit from good running wrecked plow truck out back of the shop i work for
injectors good
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Old 04-23-2012, 11:59 PM   #6
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test the fuel pressure. sounds alot like a pump.I think you may be beating a dead hose with the iac and timing
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Old 04-24-2012, 12:22 AM   #7
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Does that dist have vacuum advance?

If so, does it work? (quick check w/timing light - blip the throttle)

luck,greg
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Old 04-24-2012, 03:35 AM   #8
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Check the wires going to the MAP sensor. See if you are getting the right voltage.
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Old 04-24-2012, 07:26 AM   #9
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timing is computer controlled, your supposed to unplug the bypass set to zero, plug back in and leave alone. have you replaced the fuel filter could have junk in it from sitting.
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Old 04-24-2012, 05:35 PM   #10
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If you have a paper clip you can read codes on an OBD1 vehicle:

https://www.gmforum.com/showthread.p...bd1+paper+clip
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