Idle needle surging, but no code

Dear 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 CF4/SH, or better for the engine. There are specific oils for diesel engines on the market. Always use the multi-viscosity because it will flow and lubricate better than straight viscosity oil.

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.

Dear 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 CF4/SH, or better for the engine. There are specific oils for diesel engines on the market. Always use the multi-viscosity because it will flow and lubricate better than straight viscosity oil.

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