93 Ford Ranger 4cly. running rough and back firing out exhaust, has had a tune-up. Could the Mass Airflow cause this problem, no change in engine when unplugged.
Timing may be off. Have you checked it? Back firing could be valve timing problem; could also be too much gas-check injector spray pattern-should see a cone shaped pattern of fine mist on the throttle plates when cranking engine-this is if you have throttle body injection.
For $20-$30, you can buy a compression gauge tester and check engine compression. On a warmed up engine, pull all spark plugs, disable ignition and fuel delivery (pull injector fuse or unplug injectors), hold throttle wide open, and check compression on each cylinder by cranking engine over about 7-10 revolutions-the same amount for each cylinder, about 4-5 seconds each. All cylinders should be nearly even and balanced. Lowest cylinder should be at least 75% of highest reading cylinder. For any low reading cylinder, put a squirt of oil (about a tablespoon) in that cylinder and retest compression: if compression rises, rings are worn. If compression does not improve, valves are the reason for low compression-valves may be burnt or not sealing good.
I would do the compression test-on an engine that old, before putting expensive parts into it, you should know if the engine's internal mechanical condition is good first.
Oct 13, 2013 |
Cars & Trucks