1991 cutlass supreme with a quad 4 engine engine starts but runs rough replaced spark plugs and it didn't help. Accelerates very slowly and takes a long time to achieve thirty five mph. Any ideas?

Answer 1

Usually with symptoms like this on any engine, there is a partially blocked exhaust system. From the catlytic converter back, remove and check for blockage. Any engine running "pig rich", misfiring, lack of maintenance such as dirty air filter, will throw off ecm and cause converter to pack soot and start partial blockage. muffler baffles can rust, partially break off and block exhaust. a fully blocked exhaust will allow engine to start, run few seconds and stall.