Olds Engines: Gone But Not Forgotten
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Olds Engines: Gone But Not Forgotten

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By Larry Carley

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Times change and vehicle makes and nameplates come and go. The last official Oldsmobile rolled off the assembly line on April 29, 2004, when General Motors pulled the plug to stop the hemorrhage of red ink in their ailing Oldsmobile car division. Though the brand is now history, there are still millions of Oldsmobiles on the road that will require maintenance and repairs for years to come.

Before we get to some recent Oldsmobile technical service bulletins and other engine-related service tips, let’s take a short look back to remember the brand.

Olds History
Oldsmobile was the second major brand to join the ranks of General Motors back in 1908 (two months after Buick). The Olds Motor Works Company was founded in 1897 by an inventor named Ransom Eli Olds. He set up shop in Detroit and began to build cars for the masses. The name “Oldsmobile” was first used in 1900, and for several years Oldsmobile was the best-selling American automobile. In 1904, Ransom Olds retired from his company and founded a new venture called Reo Motor Vehicle Company to build cars and trucks. Reo was soon selling more trucks than Oldsmobile was selling cars, but Reo’s car business went bust during the Great Depression in the 1930s (the truck division was acquired by White and remained in production until 1975).

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Despite Olds’ departure from his company, the Oldsmobile nameplate under the General Motors banner continued on and continued its momentum as a leading brand as well as a trendsetter:

  • 1927 – Oldsmobile is the first car to have chrome-plated trim. Chrome was a big improvement over brass and nickel because it didn’t need to be polished.

  • 1932 – Oldsmobile introduced the first automatic choke for easier cold weather starting.

  • 1940 – Oldsmobile offered the first mass-produced automatic transmission (Hydra-Matic).

  • 1966 – The Oldsmobile Toronado became America’s first full-size front-wheel-drive car.

  • 1974 – Oldsmobile offered the first production airbag.

  • 1987 – Olds Aerotech sets a land speed record of 257 mph with a highly modified Quad Four engine.

  • 1995 – Aurora model is introduced with the new 4.0L DOHC engine and “hidden” battery.

  • 1997 – Oldsmobile is the first domestic car company to turn 100.

Differences from Other GM Nameplates
In the 1960s and 1970s, Oldsmobile engines were unique from Buick, Pontiac, Chevrolet and Cadillac engines. Oldsmobile blocks were cast from nickel-alloy iron, which made them both stronger and lighter than Chevy blocks. For this reason, Olds blocks were popular with drag racers. Even so, Chevy small blocks dominated the performance and racing industry because they were plentiful and relatively inexpensive.

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In the 1980s and 1990s, GM consolidated many of its engine designs in favor of “corporate” engines such as the 3.1L and 3.8L V6. The Olds 2.3L Quad Four, which initially appeared in Oldsmobiles, was soon offered in other GM brands.

The 3.1L V6 was used in the Olds Cutlass, while the 3.8L was the powerplant for the Eighty-Eight, LSS, Regency and Intrigue. The high output, dual overhead cam 3.4L V6 was also available in the Cutlass and Alero, though the base engine in the Alero was the 2.4L.

Aurora 4.0L V8
One unique engine in the Olds lineup was the 4.0L V8 in the Aurora. (See photo on page 28.) It is essentially a 4.6L Cadillac Northstar V8 with smaller pistons (87 mm versus 93 mm in the Cadillac). The Aurora 4.0L uses the same dual overhead cam and four-valves-per-cylinder head design as the Cadillac engine (though the cam profiles are slightly different).

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The Aurora 4.0L V8 was also Oldsmobile’s first with a PCM-controlled “oil life monitor” light. The oil change interval is based on vehicle usage and operating conditions rather than mileage alone. Up until model year 2000, the oil reminder light might not come on until the odometer hits 10,000 miles! In model year 2000, GM did away with the 10,000-mile upper limit and doesn’t turn on the oil change reminder light until the PCM thinks it is absolutely necessary. That’s probably why we’ve heard of severe oil sludging problems in some of these engines. To avoid oil sludging and premature engine failure, we think you should advise Aurora owners who drive their vehicles in stop-and-go city traffic and take short trips (especially during cold weather) to forget the light and change their oil every 3,000 miles or three to six months.

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A word of caution about flushing a sludged-up Aurora engine (or other GM engine with a similar condition): GM issued a TSB in 2001 (#02-06-01-028) that advised against flushing because “some flushing chemicals may harm engine seals and bearings.” I think most customers would rather pay to have their engine flushed than to have it rebuilt or replaced. Companies who make flushing equipment say their chemicals are perfectly safe and will remove harmful sludge and varnish deposits without any risk to the seals or bearings. We think flushing is a valuable service for high mileage engines as well as neglected engines, and can prevent more serious problems down the road.

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Aurora Head Work
If you are replacing a cylinder head on an Aurora 4.0L engine (or a Cadillac 4.6L), you may find conflicting information about the correct procedure for tightening the head bolts. The following information comes from TB 1701R published by the Engine Rebuilders Association (AERA):

  1. The cylinder head should be cleaned in solvent and dried. Discard all old 11 mm head bolts and obtain new bolts.

  2. The cylinder head and block mating surfaces should be flat and free of oil residue before the head gasket is placed on the block.

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  • In sequence, torque all bolts to 30 ft.-lbs.

  • In sequence, rotate all bolts an additional 70 degrees.

  • In sequence, rotate all bolts an additional 60 degrees.

  • In sequence, rotate all bolts an additional 60 degrees (totaling 190 degrees in steps 4, 5 and 6).

  • Torque the front three M6 cylinder head bolts to 106 in.-lbs.

    Intake Manifold Leaks
    GM has been using plastic intake manifolds on many of its late-model engines as a weight- and cost-saving measure. According to one leading aftermarket gasket supplier, many of these engines are experiencing “chronic coolant leakage issues.” In the Oldsmobile lineup, these include the 3.1L, 3.4L and 4.3L engines.

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    The intake gasket typically starts to leak anywhere from 30,000 to 80,000 miles. The apparent cause of the problem, says the gasket company, is a breakdown of the plastic-and-rubber intake manifold gasket and/or galvanic corrosion around the coolant ports where the plastic manifold mates to the cylinder head. This seems to be more of a problem in 1996 and newer GM vehicles that are factory-filled with Organic Acid Technology (OAT) coolant (Dex-Cool). The resulting coolant leak can lead to engine overheating as well as cylinder, ring and bearing damage if coolant enters the intake manifold and is sucked into the engine.

    The fix is to replace the original OEM gasket with an “improved” design that uses a special long-lasting fluoroelastomer sealing material. The new gasket also has three concentric sealing beads around the coolant ports to ensure a long-lasting seal even on heads that are slightly corroded.

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    The gasket company says its a waste of time to attempt to “patch” a leaking intake manifold gasket on one of these engines with silicone because OAT-based coolants attack silicone.

    Here’s another tip to keep in mind if you’re ever replacing an engine with a plastic intake manifold and are reinstalling the old manifold on the new engine. GM service bulletin #00-06-01-026A warns that the plastic intake manifold has a “complex inlet runner and plenum configuration,” which makes it difficult to thoroughly clean and inspect the manifold for any debris that might be inside the plenum or runners. If the old engine experienced a catastrophic valve failure, it’s possible some valve debris may have been blown back into the manifold. You certainly don’t want to suck anything into the new engine, so shake the manifold to see if anything rattles inside. If you suspect there’s debris inside, don’t reuse the manifold. Replace it, and use one of the new, improved aftermarket intake manifold gaskets we just told you about so the manifold will remain leak-free.

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    Injector Woes
    General Motors engines with Multec injectors have experienced a variety of woes, says Jim Linder of Linder Technical Services in Indianapolis. Linder presented a fuel injection seminar at last year’s International Automotive Technicians Network (iATN) technical conference in Anaheim, CA.

    Linder says he sees a lot of Multec injectors with shorted coils. “On a good day, I find maybe 30 good ones out of 100 used ones.” A good Multec injector coil should have a minimum resistance of 12 ohms. Anything less means the injector is bad and must be replaced. He says the resistance typically goes up as the injector warms up, but should not exceed the maximum limit.

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    Linder says you can tell a lot about the condition of a Multec injector by looking at its current waveform on a digital storage oscilloscope. The current waveform must always ramp up and never rise vertically. If you don’t see a “bump” in the current waveform, it means the injector is not opening. This may be due to a weak coil, low voltage to the injectors, a poor ground or too much fuel pressure. Multec injectors use a ball and seat design rather than a pintle, so there is more surface area. If fuel pressure gets up above 60 psi, it may prevent the injector from opening.

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    So what causes the coil inside a Multec injector to fail? Linder says many people think it’s because the alcohol-additives in gasoline passing through the injector are corrosive to the coil windings. This is not the case, he says, because the fuel does not touch the windings – unless the internal O-rings inside the injector fail. If that happens, it will ruin the injector windings.

    GM redesigned their Multec injectors in 1993, said Linder, and replaced the earlier troublesome “gray” injectors with ones that have a black housing. The new black injectors eliminated most of the coil winding failures, but seem to be more susceptible to clogging than the earlier design or the Bosch injectors that are used on other engines. Deposits from the PCV and EGR valves appear to build up on the injector tips and restrict fuel flow causing lean misfire. This seems to be more of a problem on the 3.1L engines.

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    “If you only replace one or two dirty injectors with new ones,” said Linder, “the new ones may flow more fuel and run richer than the old ones, upsetting the fuel mixture.” He advises replacing the entire set if several are dirty and fail to respond to cleaning. The reason is various degrees of dirty to clean injectors may upset flow rates even more, creating uneven fuel delivery cylinder-to-cylinder.

    For best performance, Linder says injectors should be flow-matched to within 2% of each other. He says the flow rates of brand new OEM injectors often vary as much as 4 or 5% from each other, which may be enough to cause a driveability or emissions problem. For more information on injector cleaning, refer to the Fuel Injector Testing sidebar on page 24 of this article.

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    Converter Failures
    We’ll wrap up our story on Oldsmobile service with a tip on the cause of premature catalytic converter failures on Oldsmobiles (or any other vehicle, for that matter). GM service bulletin #02-06-05-004A says misfire DTCs P0300, P1380 and P1381, and/or catalytic converter damage can be caused by the installation of some aftermarket alarm systems.

    GM says it has found that incorrectly installed aftermarket alarm systems “have the potential to cause misfire codes and damage to the converter. These alarm systems use a circuit interrupt that utilizes the ignition circuit on the vehicles. These alarm systems utilize mechanical relays. Normal vehicle movement can trigger these relays to engage and disengage the ignition circuit while the vehicle is in motion. These disruptions of the ignition circuit, which occur in milliseconds, may cause more fuel to be commanded. Overtime, this dumping of fuel on and off again can cause misfire codes and ultimately damage the converter assembly.

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    “GM engineering could not identify any alarms that utilize solid-state circuitry that would eliminate this concern. Because of this, it has been determined that all alarm systems must be routed through the starter circuit in order to avoid this condition.”

    Photos and diagrams are courtesy of General Motors Corp.

    Fuel Injector Testing

    One way technicians can identify clogged injectors is to do a pressure-drop test. This involves connecting a pressure gauge to the fuel rail (or teeing into the supply line), pressurizing the fuel system (by running the engine briefly or running the fuel pump), then energizing each injector one by one while noting the pressure drop each time.

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    An alternative is to remove the injectors from the vehicle and bench-test them on equipment that can measure the volume of fuel each injector flows. This is typically done on off-car cleaning equipment that flows solvent through the injectors. The injectors are mounted on a manifold that feeds solvent through the injectors into graduated glass cylinders. At the end of the flow test, the volumes are compared. Any injector that flows less than its companions needs further cleaning or replacement.

    Another alternative is automated pressure drop testing with special equipment that essentially does a flow bench test right on the engine. You don’t have to remove anything and the results are more accurate than what you can typically achieve by pressure drop testing with an injector pulser and gauge.

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