I hope you can shed some light on this one. My daughter has a 1996 Jeep Cherokee with 172,000 original miles on it, then the previous owner put in a new engine and she now has 175,000 miles. A few months back, the car started chugging/jerking when she went over 50 mph. We brought it to the mechanic and he had to replace the No. 6 spark plug as it was "burnt." She continued for about a month before it happened again. Second time, all plugs were changed, A month later, third trip back, the plugs, distributor cap and rotor were changed. Fourth time, ignition wires were changed. It has always been the No. 6 plug. Now it's in again and the mechanics (have had it to two different mechanics trying to figure this out) do not see anything wrong other than the burned plug. He has run all compression tests and computer scans and everything seems fine. There are no cross fluids (i.e.oil or water) on either side He has suggested a possible cracked head. I have been in touch with the previous owner who actually put in the new engine and he is baffled as well. Can you help at all? Any suggestions other than giving her a package of spark plugs to change every month (I would rather find out the problem!)?

This is an interesting situation. Has the shop performed an HC test at the radiator neck? That would be my first move. Secondly, do a cylinder leak down test on No. 6. If that checks out good, put a vacuum gauge on the engine which will very simply show if you have a burnt valve. Putting a scanner on the vehicle's computer, look at the fuel trim and the oxygen sensor action. You may be able to determine if the vehicle has a vacuum leak under the intake manifold. Lastly, switch the fuel injector from No. 6 hole to the No. 5 hole, and see if the problem changes to the No. 5 cylinder. If it does, you know you have a fuel injector problem.

We have a Camry that was delivered 6-1-6 (new) that only has 23,000 miles on it. The alarm is standard on the car, part of the remote entry system. Last week the alarm went off and would not stop by using the remote key. It only went off when the car was running or on the aux position. A friend, a retired mechanic, came over and disconnected the wire going to the device that produces the honking noise. Before I bring it to Toyota for repair, any ideas what the problem could be? Is it unreasonable for me to expect some assistance from Toyota or the dealer? We have been buying nothing but Toyotas since 1985.

It sounds like your car's alarm system is stuck in the valet mode or in an in-between mode. If your car's owners manual does not give you direction, you can try to disconnect the cars battery for 20 minutes and let it go back to the default mode. If that doesn't work, you may have to visit the dealer or a qualified repair shop. If you have to go back to Toyota, I wouldn't be surprised if Toyota took care of the quick reset at no charge. Right now that company is trying to get back consumer confidence. However recognize they are not obligated to do this. They have mechanics and technicians that need to bring home a pay check too. Last time I checked, no one worked for free.

Car Care Tip: You pay $29 for a car inspection. Make sure you get your money's worth for your own safety.

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Larry Rubenstein is a master technician who owns a North Shore service station. His column appears Sunday in Wheels. Write to Larry c/o The Eagle-Tribune, 100 Turnpike St., North Andover, MA 01845, or send e-mail to scanauto@aol.com

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