/I just purchased a 1991 GMC Vandura 2500 5.7 engine with 70679 miles on it. I replaced the fuel pump, O2 sensor, Temp sensor next to the thermostat new plugs wires and distributor car, MAP sensor and put a rebuild kit on the TBI it starts then immediately dies but starts rite back but idles smooth sometimes and sometimes the idle is up and down. Another thing the gasket between the tbi and intake manifold did not cover the entire base of the tbi between the two ports but around the base was covered. At highway speeds its smooth then gets rough. If i baby it it runs fine after about 50 mph but if i put it under any kind of load it tries to bog down/
1991 GMC Vandura 2500 rough and erratic idle
Apr 26, 2016
4 Replies
Fuel filter replaced? Could also be carbon holding EGR valve partially open. Manifold leak at intake port is also possible, but usually causes a rough idle at startup before ECM goes closed-loop.
replying to adule, Lincnlvr wrote: Yes new fuel filter and pump as well.
With a vehicle of that age, you may also want to check ALL of the vacuum hoses which for sure will affect performance.
replying to GeekBoy, Darrell Gholston wrote: Thanks
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