, Salem, MA

September 8, 2012

Auto Scanner: ’02 Chevy Malibu’s engine light won’t shut off

Auto Scanner
Larry Rubenstein

---- — Q: My daughter’s 2002 Chevy Malibu six cylinder car engine light stays on constantly even after replacing two catalytic converters. We have had it analyzed on a diagnostic computer and the computer keeps telling us that the problem is with the catalytic converter. What can you tell her to do to solve this problem? Is this a problem with this particular make and model of this car? It is getting pretty expensive to keep replacing converters without solving the light coming on. Any help or suggestions would be greatly appreciated!

A: Your Chevy Malibu is no better or worse than most other cars out there from that age. The fact that you have replaced the catalytic converter twice actually gives us something to work with. First of all, are you using a factory part or an aftermarket replacement catalytic converter? If you are using an aftermarket unit, you need to know that all aftermarket cat cons are not created equal. There are various qualities, just like all other parts that are available for purchase. If you are using a factory part, the next step is to find out why it keeps failing. A few common failures that can cause cat con failures are leaking fuel injector/injectors, leaking fuel pressure regulator, vacuum leaks in the engine, or a sensor giving the computer wrong information, which will cause an erroneous mixture of fuel, air, and engine timing. If your technician is not trained to diagnose the problem, there are many out there who specialize in just this kind of problem. Just a heads up; looking at the long term and short term fuel trim numbers is an excellent place to start your diagnostics.

Q: I own an ‘87 Nissan Sentra. Car runs great at first then after warming up it starts to chug and lose power, sometimes almost stalling. I did a complete tune up — no luck. One mechanic says it’s the ignition module and one says fuel pump.

A: With the information given, I can only give you generic answers. I understand that you probably don’t want to spend a lot of money on the 25-year-old Nissan. However let’s start with the necessary ingredients for a car that run well; proper air fuel mixture, proper spark timing, proper mechanical timing, and proper compression in the cylinder. A cold engine needs less of a spark than a warm engine. Thus, I feel we can probably rule out a fuel pump issue, unless it is overheating. So, taking that point of view, we have to take a look at the ignition parts such as the ignition module, distributor assembly, distributor cap, coil or even ignition wires. An old fashioned oscilloscope will give you a picture of what the engine is doing when it starts to cough and chug as it warms up.

Car Care Tip:

As we approach the autumn of 2012, you need to take a close look at your tires. Our colorful New England leaves can be hazardous when wet under your car’s tires.


Larry Rubenstein is a master technician who owns a North Shore service station. His column appears every Saturday. Write to Larry at The Salem News, c/o Auto Scanner, 32 Dunham Road, Beverly, MA 01915, or send an email to