1988 GMC Sierra help

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Old 11-08-20, 03:12 PM
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1988 GMC Sierra help

Hey everyone I need some input. I bought a 88 Sierra to fix up for my stepson and I am having some issues with it. The truck starts good and runs good when itís cold but once it warms up it stumbles and will stall at an idle. I have changed the temp sensor because it was bad I also replaced injectors because they were junk. I have replaced the engine to frame ground because that was another previous issue. I have looked it all over there are no vacuum leaks that I can hear or test by spraying starting fluid. The engine was completely rebuilt 30k ago with new cam and my friend I got it from drive it with no issues. I have found that when you apply the brake the engine dies down and idles up after you release the brake.
 
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Old 11-08-20, 03:20 PM
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I should also say that I checked the egr valve and it functions as it should when you test it but I do not have any vacuum going to the egr when starting the truck. It can be unplugged and not cause any idling issues. The pcv is good it has new plugs, wires, distributor, and fuel filter.
 
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Old 11-08-20, 04:41 PM
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Fuel filter? Spark plugs, wires and distributor cap/rotor?
 
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Old 11-08-20, 04:47 PM
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I have replaced the plugs wires distributor and the fuel filter and injectors
 
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Old 11-08-20, 08:29 PM
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try blocking off the brake booster to see if its leaking vacuum does the engine still die?
 
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Old 11-08-20, 09:23 PM
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I have found that when you apply the brake the engine dies down and idles up after you release the brake.
Booster, sounds like an area I would be looking at, vacuum leak!
 
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