4.3 ltr idles ruff

[gtmud]

I have a 91' Silver. w/156,000 on the 4.3 ltr. I have replaced all known componants(timing gears,spark plugs-A/C Delco, wires,cap & rotor, all filters) Reset timing to 0,as p/specs. Runs great down the road, at idle though, it seems a little too low. Not sure what RPM's, double checked vacuum lines. Need HELP. No engine codes.

[vnotaro]

Know this won't help much, but you're not alone. Older versions of this engine had a history of developing a rough idle. Had both an '85 and a '95 Astro van with that engine and both developed the same problem. Both were exactly like you said. Ran great but rough idle. The guy I sold the '85 to put a new engine in it at about 140k. I don't know what happened to the '95.

[gtmud]

I went through and re built the TBI, or should I say thouroughly cleaned it. The vacuum ports were all but completely clogged with carbon, and I foung the fuel regulator spring broken in 3 pieces! Still looking for the spring, will have an update if this fixes the problem.

[gtmud]

Problem fixed! Engine runs MUCH better than I expected for having 156,000! If you have a high-milage truck, with the TBI and have idle problems and such. Recommend removing your TBI, go toy our local auto parts store and purchase the "re-build" kit with about 4 cans of carb cleaner and a brass brush. It took me about 3 hours to competely clean mine(very dirty), and it runs great. BECAREFUL OF THE FUEL PRESSURE REGULATOR! THERE IS A SPRING INTHERE WITH ALLOT OF TENSION! If yours is broken, you'll need to go toyour chevy dealer to get the regulator assembly. Hope this helps some one out. It definatly worked for me.