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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: the_legend_1981 on November 17, 2007, 07:09:31 am
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i'm gonna try and make it through the winter with my straight six and put an 8 in it next year but here is the issue...when i first start driving it it's fine, but towards the end of my trip its revving real high(about 4000rpm) and if i adjust the timing a little it will idle right down. what could this be?
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4,000 rpm idle? I would say you either have a serious vacuum leak or sticking throttle/linkage/carb adjustment. Is the fast idle cam sticking?
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i'm not sure. i'm gonna check it out later... a vacuum leak could be it but why would it be fine when i'm first driving it?
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That's a lot of RPM's! Have you tried to gas it abrubtly when it is doing that, to ensure, as Vile said, the unstick the fast idle or break loose a binding in it?
When it does that, I'd get out and look under the hood and see what is going on w/ the carb.
A possibly would be a vacuum leak, but not the standard run of the mill type. I don't know how far your trip is or time-wise when it starts to run up, but, if you have a crack in the intake (which may be the same has the head on a six) or the block, it doesn't get wide until the motor heats up good. That would explain why it may not do it when the engine is cold.
With a crack, much may air get mixed w/ the fuel as if you had the throttle open.
What year truck do you have. Do you have an O2 sensor?
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Could be something sticking in your distributor like the weghts, vacume advance? First thing I would do is hose all the carb linkage down with PB Blaster.
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if i rev it up when it's doing this its like the throttle sticks
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sounds like one of two things...a cracked intake (was a BIG problem on the 250s) and as mentioned, it's not opening up until it gets hot and things expand...or a sticking fast idle solenoid. look under your hood, at your carb...there should be a small "can" with a wire going into it and what looks like a bolt sticking out of it...the "bolt" should be inline with your throttle linkage...that is your fast idle solenoid. mine started sticking and was causing a high idle...i disconnected that dude and popped the "bolt" back in...no more issues. unfortunately, that also compensates idle for the A/C so my idle doesn't increase when i have the A/C on, but it still runs fine with the A/C on...