Idle needle acts wacky

Dear Auto Doctor: I own a 2001 Honda Odyssey with 70,000 miles. The idle needle will sometimes surge up and down about 300 rpm. There are no computer fault codes and no recalls from Honda. What could be the problem? - John

Dear John: According to our Identifix database, there are a lot of faulty idle air-control motors and power-steering pressure-switch failures that do not set a fault code. The power-steering pressure switch sends a signal to the computer that you are turning the steering wheel. The computer will then raise the idle to compensate for engine power needed to turn the front wheels. The technician should be able to connect the scan tool and observe the readings from both the idle air-control motor and the power-steering pressure switch.

Dear Doctor: I drive a heavy-duty pickup truck in the scorching Arizona heat. It’s a 2005 Dodge Ram 3500 with the 5.9 Cummins Diesel engine. I was at the dealer getting the truck serviced, and I asked for the “full-synthetic” oil. When I got the bill of charges I noticed they put in “regular-synthetic” oil. They recommended against full-synthetic for this engine. I have always used full-synthetic oil in my vehicles. What do you think? - Ralph

Dear Ralph: You can use regular-synthetic oil, as long as it meets the requirements CF-4/SH or better for the engine. There are specific oils for diesel engines on the market. Always use the multiviscosity because it will flow and lubricate better than straight viscosity oil.

Dear Doctor: As a female reader, I really enjoy your articles. My husband gets a big kick with my new knowledge from your columns. What is the best way to go about installing a tilt-steering column in a 1962 Chevy shortbed pickup? My husband and I are also installing a power-steering conversion kit. We have installation instructions for that, but not for tilt-steering. - Arlene

Dear Arlene: I’m very happy that you are becoming better informed on auto repair and maintenance from my weekly column. This is a simple task on tilt-steering installation. You can either buy a new custom steering column or a used steering column from a salvage yard. This change-over will take less than two hours.

Dear Doctor: I own a 1998 Mercedes-Benz ML 320. The problem I have is with the keys suddenly not working. Each time the key fails, I have to purchase a new one from the dealer. I have used up all the key codes that can be matched for this vehicle. Now I have to replace the system at a cost of $2,000. Is there any other way around this problem? - Theresa

Dear Theresa: On a lot of today’s vehicles, there is a limit to the number of times keys can be programmed to a vehicle. When the number of replacement keys is met, the ignition switch system has to be replaced. It seems the more expensive the vehicle, the more expensive the key and switch replacement are, so unfortunately, there is no getting around that $2,000 expense.

Dear Doctor: My 2001 Pontiac Montana minivan has 84,000 miles. About six months ago, the gas gauge stopped working consistently. The gauge will seem to register correctly sometimes for a few minutes once the car starts from cold, but then jumps up to full - no matter how much fuel is in the tank. Now it has even started falling to empty, kicking off the lights and bells for low fuel even if the tank is more than half full. I understand the mechanism is located in the gas tank. What are my options other than removing the gas tank at great expense? - Mike

Dear Mike: After the technician checks the problem with a scan tool and verifies that the in-gas-tank fuel module is the problem, then yes, removal of the gas tank is required. A new original GM gas module with sender will be installed, and your car is fixed. I recommend a gas-filter replacement when a new pump is installed. I also suggest a new external gas filter every 20,000 miles or two years, whichever comes first. There is no other option on a fuel-module replacement on this vehicle.

• Junior Damato is an ASE-certified master technician. E-mail questions to info@motormatters.biz.