89 Suburban idle and shift issue
July 1st, 2010, 2:47 PM
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89 Suburban idle and shift issue
Hey all, just joined.
My dad has an 89 Suburban with a Vortech 350 and a THM400 that has developed an erratic idle and shift behavior. Sometimes when coming to a stop the engine will bog and surge, like it hasn't downshifted into first and is trying to keep itself from stalling. Also, when accelerating lightly the transmission will upshift normally, albeit a little bit late, but if the accelerator is pushed more than about halfway it will downshift a gear and say there no matter how high the RPMs are until the gas is released, even on a flat surface. When it does shift, the shifts are solid.
We're thinking it's a vacuum leak, is that what it sounds like to you guys? Does anybody have a *GOOD* vacuum line diagram?
My dad has an 89 Suburban with a Vortech 350 and a THM400 that has developed an erratic idle and shift behavior. Sometimes when coming to a stop the engine will bog and surge, like it hasn't downshifted into first and is trying to keep itself from stalling. Also, when accelerating lightly the transmission will upshift normally, albeit a little bit late, but if the accelerator is pushed more than about halfway it will downshift a gear and say there no matter how high the RPMs are until the gas is released, even on a flat surface. When it does shift, the shifts are solid.
We're thinking it's a vacuum leak, is that what it sounds like to you guys? Does anybody have a *GOOD* vacuum line diagram?
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