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post #1 of (permalink) Old 11-16-2003, 11:48 PM Thread Starter
 
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GMC 2500 5.7 L chugging like a locomotive

When I started driving, the choke knob had the most influence over the air-fuel mixture. On my 94 GMC 2500 5.7 L what would it be. Does 1 sensor have more influence than the others? Something is not telling the computer to lean out after warmup. Someone suggested that it was my crank postion semsor located at the front of the engine by the balancer. I can't find anything with a plug near the balancer at all, but there is a mystery wire with a broken piece of grey ceramic still plugged into it. The wire branches off the harness right beside the temp sensor on top of the dome near trhe thermostat, right up front. The plug will only reach 8 inches from the temp sensor and I can't find anything. I assumed it was off of the A/C compressor. The truck still runs great when cold, then gradually craps out as it reaches temp and then won't idle and will barely run and has no power. Any ideas?????
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post #2 of (permalink) Old 11-17-2003, 09:01 PM Thread Starter
 
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Re: GMC 2500 5.7 L chugging like a locomotive

Keeping this fresh in hope of a solution.
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post #3 of (permalink) Old 11-18-2003, 12:22 AM
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Re: GMC 2500 5.7 L chugging like a locomotive

what is your timeing set at,?

I wouldnt do the toggle switch,

vacuam leaks?

spark plug wires crossed?



to me it sounds like a timeing problem, with the vacuam advance hooked up can you keep it running by keep the throttle up, or do it just always die after 30 seconds no matter what
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post #4 of (permalink) Old 11-18-2003, 09:08 AM Thread Starter
 
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Re: GMC 2500 5.7 L chugging like a locomotive

We unplugged the little wire under the dash and checked the timing with a light and it was bang on factory specs. We also checked for vacuum leaks and took all hoses off 1 by 1 and checked and found no leaks. We checked the fuel pressure and it was 13 psi, the manual wants 9-13 so it is fine. The plug wires are in the right spots. Last night the engine started missing, like now it's dragging a cylinder or 2. On the weekend it ran smoothly, no missing, until it started loading up. I'm a pre-injection boy and when it starts to screw up my brain tells me that I forgot to push the choke knob in. Now that it's dragging a couple of barrels I think that a couple of plugs have fouled from all the idling with the diagnostic computer attached.
The truck will stay running if you tap the throttle to clear it out and is driveable if you keep the rev's up but I need one foot on the gas and one on the brake when I pull up to an intersection. Just before it quits it runs terrible but as soon as you touch the key to restart it fires up and idles perfectly - for 30 seconds. When it's -10 or -20 it has great power and idles for 5 minutes until it warms up. That makes me think it's running too rich, cold good hot bad
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post #5 of (permalink) Old 11-18-2003, 11:29 PM
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Re: GMC 2500 5.7 L chugging like a locomotive

the vacum advance wire isnt under the dash
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post #6 of (permalink) Old 11-19-2003, 07:46 AM Thread Starter
 
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Re: GMC 2500 5.7 L chugging like a locomotive

Well, the computer is under the dash behind the glove box. There was one wire that wasn't completely taped up in the harness and it had a little plug on it so I figured it must be the one. When we unplugged it the timing was stable under the strobe and when we plugged it in the timing varied which also made me think it was the right wire. Where should I look for the right wire?
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post #7 of (permalink) Old 11-22-2003, 08:26 AM Thread Starter
 
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Re: GMC 2500 5.7 L chugging like a locomotive

Still lookin for answers.
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post #8 of (permalink) Old 11-22-2003, 01:40 PM
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Re: GMC 2500 5.7 L chugging like a locomotive

I guess its possible thats the right wire. but the wrong place. if you stand in front of the truck its on the right side of the motor. its got a plug in deal, I cant remember if its a brown or purple wire. its one wire by it self comeing from the harness
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