It always bothers me to see the post of yet another victim of GM's poorly designed 4.3 Vortec V-6. (See the post entitled "99066F: Is this GM recall real??") With the exception of the GM passenger car diesels, I feel that the 4.3L Vortec V-6 is possibly the biggest lemon that any vehicle manufacturer has ever palmed off its unsuspecting customers. I am offering my negative experience and negative opinions of the 4.3 Vortec V-6, but I would welcome any feedback.
The 4.3 Vortec V-6 is often referred to as a "Baby 350", when in fact, it is nothing more than a bastard child. Two cylinders were cut off of the 5.7L (350 cubic inch) V-8, to create a 4.3L (265 cubic inch) V-6. But the problem with this design is that the 5.7 V-8 is a balanced engine (two pistons up/two pistons down -- two piston up/two pistons down), but the 4.3 V-6 is an unbalanced engine (two pistons up/one piston down -- two pistons down/one piston up). This V-6 imbalance is made worse due to the massive size and huge displacement of the 5.7L pistons and GM has been unsuccessful in its attempts to get the 4.3 engine to stop shaking. The inherent failure of the 4.3 engine design was addressed by GM when it released its smaller 4.8L (295 cubic inch) V-8 engine. The 4.8L V-8 is 30 cubic inches (11%) larger than the 4.3L V-6, but it has 33% more cylinders. As a result, the operation of the
4.8L V-8 is smooth and quiet, while the 4.3L V-6 is rough and noisy.Around 1990, GM was very concerned with producing a low-priced, full-size pickup which would deliver unusually-high gas mileage. This gas miser would then be used to offset GM's extremely profitable gas hogs. In order to accomplish its goal, GM introduced a C1500 pickup which would actually deliver its 18/24 MPG rating. This gas-saving, loss-leader was built around a 160 HP 4.3 Vortec V-6, with a Getrag
5-speed manual transmission and a standard 3.08 differential. The key to higher gas mileage figures, for all GM truck engines, was the Getrag 5-speed manual transmission, which delivered 15-20% higher gas mileage than trucks with automatic transmissions. GM was so anxious to produce this gas-saving, manual transmission vehicle that it offered a $1500 "Manual Transmission Bonus Package" incentive, which lured in suckers, such as myself, who bought the atrocious 4.3 Vortec V-6.For some reason, my 1990 Chevrolet C1500 California 4.3 truck came with a smog pump, while other 1990 C1500 models with 5.0 and 5.7 V-8 engines did not have smog pumps. This smog pump robbed the 4.3 of power that it couldn't spare. My original 4.3 was the epitome of the old joke that GMC stands for Garage Man's Companion. My first complaint of constant 5th gear pinging was remedied by the dealer by retarding the spark. The pinging didn't go away and retarding the spark made the truck feel like it was pulling a trailer. I endured the pinging and low power for a month. Then, through a stroke of luck, a mechanic discovered a service bulletin which revealed that GM had released a new PROM for my vehicle which was designed to correct an engine flare that occurred when shifting between gears with a manual transmission. Even though my truck didn't have this shifting problem, the service manager reasoned that the new PROM might have other re-designed features which could fix the pinging. Fortunately, he was right.
My 4.3 was mechanically-noisy, especially so after a cold start, when the engine would race uncontrollably at a high idle until it warmed up. The engine also vibrated badly, particularly in the 1200 to 2000 RPM range. To my dismay, a GM service bulletin revealed that this was a "1200 RPM Shake" and that this severe vibration was considered to be normal operation for the 4.3. The engine speed compensation never worked when the air conditioner was operating, so the engine would buck and jerk when shifting gears when the compressor was engaged. When the truck was stopped in traffic, the compressor would drag RPMs down to the point of nearly killing the engine. I would either have to speed up the engine by pressing down on the gas pedal or turn off the AC when stopped in traffic. The dealer was never able to fix this problem.
After 106 thousand miles, the 4.3 Vortec V-6 developed a loud knocking noise and removal of the valve covers revealed that the engine had a dry side. One side of the engine was clean and gleaming with oil, while the other side was charred and blacked due to oil depravation. I had religiously changed the oil and filter every 2500 miles, but to no avail. The engine was ruined and would have to be replaced.
I decided to go with a Goodwrench rebuilt engine, however, the dealer told me that the original 1990 4.3 had been replaced with an "improved"
200 HP version. I think he mentioned something about a "roller cam", but I'm not sure. In any event, the new engine did have more power, but it used more gas. Then, after 6000 miles, the Goodwrench engine spun a bearing and needed to be replaced under warranty.The next Goodwrench engine ran well enough for 110 miles, but it was starting to use oil. The "1200 RPM Shake" and air conditioning problems continued to plague this engine, as well. Finally, in February 2004, the vehicle was branded as a "Gross Polluter" and I was only able to get $1000 for it from a wholesaler. I disclosed this SMOG problem to the man who bought my truck, but because the truck scored well in the hydrocarbon section and had only failed one of the NOX tests, he thought that the problem would be relatively simple to fix -- maybe a loose vacuum hose or a bad catalytic converter. It turned out that he needed to spend over $1300 to get the truck smogged. Fortunately, he was still able to sell the truck for a modest profit.
While I see others who have gotten 200 thousand miles of trouble-free miles from their 5.7 (350) engines, I had to suffer through three 4.3 V-6 engines to obtain the same mileage. The money I saved on gas was more than offset by the downtime and expenses that I incurred while dealing with the deplorable 4.3 Vortec V-6.
My overall feeling is that the 4.3 Vortec V-6 is a piece of crap. I would be interested in hearing from anyone who has a 4.3 Vortec V-6 story to tell.