Join Date: Apr 2002
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Re: 4.3 acting up
The most common answer that someone will offer up in your time of need is a "clogged cat"... Loose Translation: "I DON'T UNDERSTAND THE TRUE OPERATION AND FUNCTION OF AN INTERNAL COMBUSTION ENGINE, OR ITS EMISSIONS CONTROL COMPONENTS, but... I KNEW A GUY WHOSE BROTHER'S NEXT DOOR NEIGHBOR'S AUNT'S COUSIN'S BUCTHER'S HAIRDRESSER HAD THE EXACT SAME PROBLEM (even though it was an Asian car that had all the Autozone engine-mod goodies that were available, and actually burned up the engine and exhaust while drag racing a soccer-mom's bone-stock Cavalier that her delinquent son "borrowed" for the night to race down the local dark, dippy, and just-a-little-bit-unsafe road)." [img]images/graemlins/confused.gif[/img] People just like saying Catalytic Converter, because they think it sounds cool...
Chilton's Service Manuals will give you just about all the info you'll ever need to complete your own repairs, and you can usually come up with a more accurate diagnosis if you dig in and work at it yourself.
A Catalytic converter hardly ever fails, especially on a Chevy. The typical GM Truck Cat is not a honeycomb type... it has ceramic balls in chambers that the exhaust gases pass through. Pollutants are broken down and modified or consumed, for the most part, by the Cat, hence the Catalytic effect, and the creation of water that drips from the tailpipe. A failed Cat will usually be caused by: 1. Low quality fuel, 2. Continuous use of improper (low) octane level fuel, 3. Fuel system malfunction, which will cause a runs-lean or runs-rich condition, or 4. An excessive oil consumption or internal oil leak concern, where the oil will accumulate in the Cat, causing exhaust overheat and Cat meltdown.
An easy test for the Cat: Does water drip from your (a person's) exhaust? If so, then the Catalyst Emissions system is functioning the way it was designed and is most likely ok...
Now, to your truck... Is the truck out of fuel, or is the fuel old (both common with vehicles that have been sitting)?
You have what is called the "Triangle of Combustion", and at each point of the traingle is a vital component of the proper function of an engine, based on the fact that it's mechanically sound. At the points, you have fuel, air, and spark.
If the engine didn't make any funky or loud noises just before it quit running, you are probably safe in assuming that no mechanical failure has occured. From that point, dive in and check for spark @ the coil, check for fuel that should be clean and strong-smelling, and properly delivered to the TBI unit. Air delivery is simple... is the air intake blocked off, or did a bird get sucked into the TBI unit? [img]images/graemlins/smile.gif[/img]
You'll find that the 4.3 is a very good engine, and can produce more horsepower in a bone-stock normally-aspirated pickup than the new supercharged Nissan v-6 pickup can.