8 Engines That Missed

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Fuel Economy > Fuel Economy

Automotive News / April 11, 2005

When an automaker develops an engine with huge flaws, the consequences can be severe. Many consumers still think poorly of diesel techology because engines designed by General Motors from 1978 to 1985 clattered and belched smoke.

More stringent durability testing and improved design technology now make such instances rare.

But that didn't stop Staff Reporter Richard Truett from putting together his eight picks for the poorest car engines of the last 50 years.

1. GM's diesels - Responding to the fuel crisis of the late 1970s, GM rolled out a 5.7-liter diesel engine designed by Oldsmobile. The V-8, produced from 1978 to 1985, was based on a gasoline engine. That was a terrible miscalculation.

The block, though beefed up, could not stand the stress and strain of the high-compression diesel pistons. Cylinder-head bolts broke. Gaskets blew. Crankshafts failed. Engines overheated.

The fuel system may have been the source of many of the problems. A poorly designed fuel pump, combined with a poor filtration system, let water into the fuel and left many diesel-powered cars limping and spewing smoke. Or worse, they croaked - a big embarrassment for GM. Disgusted owners yanked out the diesels and replaced them with gasoline engines.

GM had two other diesel engines, a 4.3-liter V-8 and 4.3-liter V-6. Neither fared much better than the 5.7-liter V-8. By 1985, GM's engineers had solved most of the problems. The 5.7-liter diesel was reasonably reliable, and it delivered fuel economy of about 30 mpg in GM's large cars. But by then the damage had been done.

Not only were GM's diesels out of production, but sales of diesel-powered cars from every automaker, especially Mercedes-Benz, which built the best diesels in the world, also were in major decline. It would be 20 years before another automaker, Chrysler, would launch a diesel engine in a small vehicle. The Jeep Liberty diesel went on sale in January.

2. Triumph Stag 3.0-liter V-8 - In the early 1960s, British carmaker Triumph laid down its engine architecture for the next decade, which included an overhead-cam V-8 and four-cylinder variants using many of the same internal parts. The engines were designed before the cars in which they would be used.

Big mistake.

"It's always a bad idea to compromise basic engine design to fit a package," observes England-born Dave Szczupak, Ford Motor Co.'s vice president of powertrain operations.

In 1971, Triumph was poised to become Britain's equivalent of BMW. The classically styled Stag roadster was Triumph's big move upmarket. The Stag overhead-cam V-8 might have been a decent engine had it not been for a last-minute decision to increase displacement from 2.5 to 3.0 liters, thereby designing the engine around the car. That was a crucial mistake, Szczupak says.

The increase in displacement coupled with some truly bizarre engineering overstressed the engine. The engine suffered from severe overheating problems, failed crankshafts and weak timing chains. The inefficient gear-driven water pump sat vertically between the cylinder banks, which often led to air being trapped in the cooling system.

But the biggest gaffe was in the way the cylinder-head bolts and studs were arranged. The bolts went straight through the head in the typical way. But the upper row of studs went through the head at an angle. This arrangement made it nearly impossible to get a good seal between the aluminum heads and cast iron block, so coolant leaks that led to overheating were common.

By 1973, the Stag was gone from U.S. shores. By 1977, production stopped globally after about 26,000 cars had been built.

3. Chevrolet Vega 2.3-liter 4-cylinder - Not to be upstaged by the British, GM engineers fired back with the 2.3-liter, overhead-cam, aluminum-block iron-head engine in the 1971-77 Chevrolet Vega. Few consumers griped about the car's scaled-down Camaro appearance. And the Vega wasn't any more rust-prone than various Datsuns and Toyotas of the day. Plus it was priced right.

But the engine doomed the car and badly tarnished GM's engineering reputation.

The big mistake was GM's failure to use steel cylinder liners. Instead, the pistons ran on acid-etched, silicon-treated aluminum. Engines overheated and blocks broke.

When the engine did run, it often clicked, knocked and shook like an out-of-balance washing machine. Many engines also burned oil profusely.

By 1976, GM had installed steel cylinder liners and worked most of the kinks out of the engine, but it was too late. Since the Vega, engineers have perfected the technology that enables aluminum engines to be built without steel cylinder liners, says Thomas Stephens, group vice president of GM powertrain.

Sadly, more bad GM engines were just around the corner.

4. Cadillac V-8-6-4 - In the early 1980s, Cadillac started to feel the heat from Mercedes-Benz and BMW. Already bruised by the diesel debacle, Cadillac wanted to make a grand engineering statement.

The V-8-6-4 - GM's first attempt at cylinder deactivation - did make a statement, but not the kind that Cadillac wanted. The engine bucked and jerked. The transition of the cylinders turning off and on was so rough and unreliable that it angered many Cadillac owners.

But the idea behind the V-8-6-4 - to shut off the flow of oil to the lifters and close down cylinders - was a good one. Unfortunately, the sensors and computing power to make the system work seamlessly just wasn't available back then.

Flash-forward to today. GM is in production with its Displacement on Demand cylinder-deactivation system on its mid-sized SUVs. Powerful computers shut off the flow of oil to the valve lifters, which turns off half the cylinders when at highway cruising speed. This gives about a 5 percent fuel economy gain and costs GM just $50 per engine to install.

The system works so smoothly, drivers don't know it's there. Chrysler has a similar system for its hot-selling Hemi V-8s.

5. Toyota 3.0-liter IMZ V-6; 5SFE 2.2-liter 4-cylinder - Both these engines are prone to filling with oil sludge and seizing up in 1997-2002 models, though Toyota says the engines aren't faulty. Toyota blames owners for not changing the oil often enough or for using the wrong oil. Many experts disagree. They say a defect in the breathing or circulation system is the likely culprit.

Toyota did make a few improvements to its engines that seemed to solve the problem. The company has spent millions fixing ruined engines and trying to satisfy angry owners. About 3.3 million Toyota and Lexus owners were given extended warranties, and more than 4,000 engines were replaced.

6. Hyundai Excel 1.5-liter 4-cylinder - The 1.5-liter four-cylinder engine built in Korea under license from Mitsubishi Motors Corp. for the 1986-94 Hyundai Excel was a sound design. The engine performed well in the Mitsubishi Precis but suffered major quality problems when Hyundai manufactured the engine. Early Excel engines leaked and burned oil, dripped coolant, overheated and sounded like badly adjusted sewing machines. Most of the leaks centered around the cylinder head. That poor quality hobbled Hyundai's growth in North America and was one of the reasons that Hyundai created its trendsetting 10-year, 100,000-mile powertrain warranty.

7. Chrysler Imperial fuel-injected V-8 - The 1978 Chrysler Imperial - a big, stylish coupe - was powered by a 318-cubic-inch V-8 that featured Chrysler Corp.'s first electronic fuel injection system. Stalling, surging, failure to start when hot and dealerships that could not make repairs doomed the car.

Chrysler recalled the Imperial and replaced the troublesome fuel injection system with a tried-and-true low-tech carburetor.

Bob Lee, Chrysler group's vice president of powertrain product engineering, says of the technology: "It was very clever. Unfortunately, it didn't work very well."

He adds: "At least we didn't sour the industry on fuel injection."

8. Pontiac Fiero 2.5-liter 4-cylinder - The only way to fit an engine on the 1984-85 Pontiac Fiero chassis was by using a new and smaller oil pan holding three quarts of oil instead of the typical four. No problem as long as the owner kept the oil level full. The problem was that many Fiero drivers didn't. Moreover, some of the so-called "Iron Duke" engines had been built with defective connecting rods, which snapped when the engine ran low on oil. Broken rods flew out the side of the block and caused fires.

The episode ruined an excellent launch of what could have been one of Pontiac's biggest successes of the 1980s.