frustrating chevy

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Old 11-09-06, 07:06 PM
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frustrating chevy

i have a 1988 gmc 1500 5.7 4x4 auto w/od my problem is it runs like crap at low speeds and at idle sometimes stalling when braking i have changed plugs,wires,cap,rotor,fuelfilter and checked timing with timinglight any suggestion's would be very helpful
 
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Old 11-10-06, 06:03 AM
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Mileage ?
 
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Old 11-10-06, 06:10 AM
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Sounds like there may be a vacuum leak someplace

That would cause rough running at low speeds. The rubber hoses get brittle after a while and start to crack. This can be difficult to track down. One method is to spray WD40 along the vacuum hoses and if all of a sudden the engine starts running smoothly then check that area of the hose.
 
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Old 11-10-06, 04:32 PM
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the truck has 156,654 miles
 
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Old 11-10-06, 08:52 PM
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Does your engine have an EGR valve. (Exhaust Gas Recirc Valve). Traditionally I'm a Ford guy and Ford's have EGR valves that stick open alowing a large hole to the intake manifold.
The effect is rough idleing and stalling at low speeds but fine when accellerating.

Just a thought.
 
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Old 11-10-06, 09:00 PM
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I hate to say but you may need a valve job.
Do a compression test. Should be around 170 PSI at each cylinder.
The PSI readings will be lower on high mileage engines.
Actually I think 170 PSI is kinda low.
180 ~ 190 PSI is very good.
You don't want to see big diffrences between the cylinders.
Look for consistency.
 
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Old 11-11-06, 05:05 PM
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yes it does have an egr valve but i checked it maybe get a new one any how
 
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Old 11-11-06, 08:24 PM
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Has this engine ever been rebuilt? If not it may be time to put some money into it. Does it idle to low?
 
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