Question about 1996 GMC Sierra

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Replaced 305 engine with 350, runs poorly at steady speeds

I rerplaced a 305 engine in my 1996 GMC 4x4 with a 1998 350 engine. It idles great, it accelerates great, but feels like it has the "hiccups" at a steady speed. The distributor and plugs and wires are relatively new. The engine runs very smoothly at idle, whether in park or in gear. Could this be related to the computer? I've been told it is not necessary to replace it, but I wonder if there is some difference between the computer on a 305 as opposed to a 350. I would appreciate some help as to what to do next.

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Try replaceing/testing knock sensor, unless you already did

Posted on Mar 07, 2009

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