1994 GMC 3500 5.7 wont stay running in gear or under power

daviedude · April 20, 2015

I have a 1994 GMC Sierra with 5.7L TBI . Issue is the truck will start and idle but as soon as you put into any gear the truck stalls out unless you give it gas, it will idle rough in gear however whenever you try to apply power the motor runs super rough as if it was running on 2 cylinders, not smoking at all as it would if running rich so not flooding, here is what has been changed and checked , Fuel pump replaced and retested holds 12 psi , replaced the following, O2 sensor, map sensor, temp sensor, regulator , pcv ,cap rotor coil wires plugs, iac, im sure ive missed a few sensors but every electrical component on the computer system changed except computer and injectors , injectors are equal and reactive with a great mist no streams or drips, also did new electrical leads to the injectors , great compression in all cylinders. I also noticed the temperature gauge in the cab does not work but the lead wire to the sensor does have 5 volts coming in. Have tested for major vaccume leaks around the intake and have found none. At this point im lost and have no other direction to go , if anyone has any ideas im open to try them , truck only has 86 k on it , thanks .

00Silverado4x4 · April 21, 2015

What about engine timing?

daviedude · April 21, 2015

What about engine timing?

Did not check the timing since the distributer was not loosened or disturbed , however I will check and report back.

daviedude · April 21, 2015

What about engine timing?

checked the timing and found it to be at 8 degrees so I corrected it back to 0 degrees as the specs say however no change at all in the symptoms.

daviedude · April 23, 2015

bump

00Silverado4x4 · April 24, 2015

What about the fuel filter? When was that last replaced?

daviedude · April 25, 2015

replaced all the fuel lines and filter at the same time

00Silverado4x4 · April 27, 2015

Sorry, I'm out of ideas personally but hopefully someone with more knowledge will have some other ideas.

grampadirt · April 27, 2015

Have you checked the Throttle Position Sensor?The Ignition Control Module?

daviedude · April 28, 2015

have not checked or replaced the ICM however the TPS has been replaced and is working as I do get a profound response when unplugged. I was going to take some time and buy 8 spark testers to watch the spark as the truck runs to see if the spark is fading when under power. Once I get the testers and see ill report back.

Lazarus Long · May 8, 2015

Different system than yours, but when my 97 had similar rough running issues new plugs and wires fixed it.

C1500ownerAZ · September 22, 2015

I have the same problem. And am also tryin to tackle this. one of my cylinders has low compression. Have you checked compression? I still gotta tear apart my top end and check the rings. Try to check compression first should b round 150psi If I remember. Sorry if I'm wrong. Ha

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