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Followup To
Question -
I have a '94 Astro van, 4.3 engine, vin (w), vortec engine, fuel injected with a cmfi fuel injection unit (single fuel injector with 6 poppet valves).
Van backfires pretty regularly under the following conditions:
Warm engine, highway speed (55+ mph), if I take my foot off the accelerator and coast, when I hit the accelerator again, van backfires. Doesn't happen at lower speeds or when engine is cold.
Also, van smells very "gassy" when idling, and exhaust has a lot of black soot.
I did a full tune up - plugs, cap, rotor, wires, air/fuel/oil filters, and have had the fuel injector unit replaced...All this and the van does run a little better, but backfiring problem is the same.
Any ideas?
Thanks, Izzy
Answer -
Do any of the plugs appear to look a different color at the electrode unds ?.
Could be EGR problems.
Could be ignition timing.
Could be a fault in one or more of the injection units.
Without personally performing some tests, It is hard to say what it could be.
autohelp
Thanks. The plugs were pretty black, but I changed them. Also, this van has a central fuel injector with 6 hoses and a poppet valve at the end of each, but that was just changed too, and my mechanic said that he cleaned out the egr valve. I'm glad that you and him are on the same page. I'm trying to figure this out myself because my mechanic has looked at this several times and I'm getting a vibe that he's kind of tired of looking at this vehicle.
Should I check the timing next?
Izzy
AnswerBlack fouled spark plugs are a sign of to much fuel, Low ignition to the spark plugs, incorrect ignition timing, EGR and exhaust restriction.
Did you TEST BOTH o2 sensors ?.
Another thing you might want to try is what called TOP ENGINE CLEANER of which removes heavy buildups of carbon deposits from on top of the pistons as this can also cause your type of problem.
autohelp
