Join Date: Jan 2003
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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