Q My 2003 Jetta Turbo started sputtering, then smoke billowed out the back. The dealer replaced the head gasket and during testing the computer failed, so he replaced it. I’m worried my car could do this again since the cause wasn’t determined. What do you think could have created this problem?

KATHI BERGER   
   Sacramento, California  

A Like Laurel and Hardy, a failing computer can create a chain of escalating misfortunes, each building on the one before. In this case, it might cause the engine to run hot, perhaps by making the fuel mix either too rich or too lean. The heat could prove fatal to the head gasket, which would then let coolant leak into the combustion chamber. This would produce a sputtering engine that blows billows of water vapor out the exhaust. Or the computer could have let the turbo build too much pressure in the engine, leading to a similar string of events. And head gaskets have never needed high-tech help to fail; they can spring a leak with no outside encouragement at all. Still, it’s unlikely that such trouble would strike twice in the same place.

Q What could be making the suspension on my 2002 Ford Explorer intermittently groan and squeak when I’m driving over slight bumps and dips at low speed?

STEPHEN REGGINELLO  
Sandy, Utah  

A Worrisome sounds often make themselves heard at low speeds because wind and tire noises are so reduced that they no longer mask creaks, groans, or squeals that may have been there all along. Belts, suspension parts, or other components can make such sounds as they cry out for attention.

In a vehicle as new as this one, the cause of suspension noises is probably something simple. For example, spring mountings could be out of position. It’s also possible that harsh weather has caused some rust buildup. Have the tie-rod ends and ball joints lubricated. Rubber components, such as control arm bushings, should be sprayed with a silicone lubricant. Finally, check with the dealer to see if there has been a service bulletin covering this problem.

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