Stalling Camry May Have Faulty Injection Switch

QUESTION: My 1986 Toyota Camry has a cold-starting problem. It stalls, runs rough and hesitates until it reaches normal operating temperature. I have had my mechanic look at it, but I can’t seem to get the problem fixed.

Do you have any suggestions?

I. P.

ANSWER: The Camry’s fuel-injection system has a separate injector for cold starting; it is controlled by a switch that may be at fault.

The switch senses the car’s coolant temperature and provides a little additional fuel for the engine until it reaches a predetermined temperature. Once the switch senses the coolant warming up, it disconnects the cold-start injector. But the temperature parameters for the heat switch are fairly narrow, and the system doesn’t work particularly well.

By 1987 Toyota had replaced the switch with one that has a wider operating window and a more sophisticated engine-temperature profile built into the engine’s computer software.

You should have a qualified mechanic make sure the switch is still operating properly and determine whether the later switch can be placed into your engine.

Q: A car salesman recently said that the engine in a particular model does not have a Siamese-bore engine block, which he said is a big advantage. I thought I was pretty smart about cars, but I had no idea what he was talking about and didn’t want to let on.

Could you tell me what a Siamese engine is?

J. N.

A: It is difficult to say whether the engine block without a Siamese bore is better or not.

In the vast majority of engine blocks, each cylinder is separated from the others by a water jacket. The water jacket envelops the entire cylinder, allowing coolant to provide uniform cooling to the cylinder. In a Siamese-bore block, however, the walls of two or more cylinders touch each other. The advantage of such an arrangement is that the engine can be more compact and lighter, an important issue in many front-wheel-drive engines that must fit under small hoods. The disadvantage of a Siamese-bore engine is that it must be precisely engineered to avoid a localized overheating problem.

The point at which the two cylinders touch would obviously have a much greater probability of overheating, with the attendant problems of accelerated ring and piston wear. Engineers insist that a Siamese-bore arrangement is not inherently bad and that a properly designed cooling system can ensure that the engine will not wear out prematurely.

It comes down to your faith in the manufacturer of the engine and the track record of the particular engine. Like so many technical issues on new cars, this one is beyond the ability of most motorists to evaluate.

Q: In 1990, I purchased a new Acura Legend. The owner’s manual states that I should use only SG grade oil. But I still have two cases of a top quality oil in my garage that is rated only SE-SF.

Is there any substantial difference in the two grades, and can I use it in my Legend?

E. B. S.

A: You really should use SG grade because the SF is not up to the manufacturer’s standards, particularly in such important areas as engine sludge control. The two cases of oil couldn’t be worth more than $30, which is hardly worth risking damage to a car worth more than $30,000.