summershandy

At around 30-40 mph the engine wants to kinda jerk/hiccup/lurch until I give it more gas. Runs great at idle and highway speeds. Not the transmission cuz I can make it sputter in park at around the same rpm until I rev it more. Mechanic buddy thinks map sensor or vacuum leak........thoughts?

canucklehead

Could also be a bad injector dribbling gas instead of spraying it.....You could watch and see, and swap injectors if necc.

summershandy

Thanks, will check that too!

SBchevyfan

I would check your fuel pressure. At 30-40 mph you are not turning very high rpms. At highway speed your engine is turning faster and is actually creating a suction to help draw fuel in. I had similar problems with my 88 and 89 Caprices. Both were fixed with a new fuel pump. Each had about 125,000 miles when the fuel pump went.

summershandy

Duly noted.....the engine idles with no problem however. When I had a pump go in a 79 - 3/4 ton it would starve at high speeds. All suggestions welcomed and it's going in next week. I'll post our findings.

summershandy

Mechanic found a rusted out pick up plate under the distributor. Apparently quite common so we changed that. Symptoms still persisted. Unhooked the vacuum line to the EGR valve, plugged it and ran great. He recommended leaving it that way but "service engine" light came on. I installed a new EGR valve and so far so good. Hope others check this fix first.