- The Washington Times - Friday, August 21, 2009

Dear Doctor: I have a noise problem with my 2001 GMC 2500 heavy-duty pickup with 120,000 miles and the Duramax diesel engine. The noise started about a year ago and it seems to be coming from the engine compartment. My dealer replaced an encoder motor at a cost of $800, but it didn’t stop the noise. I tried two other diesel specialists, with no luck. So far I’ve spent about $1,200 and the noise is still there. Performance-wise the truck is fine, mileage is good. I tow a 12,000-pound fifth-wheel and I’m concerned that it will break down on my way to Florida this winter. Mario

Dear Mario: Without me personally hearing the noise, it is impossible for me to help. What I can tell you is to go to a shop that uses a stethoscope - just like a doctor - to locate the source of the noise. You can also go to any good auto parts store and purchase one yourself so you can hear the source of the noise. Be aware of moving parts, such as the cooling fan and fan belt.

Dear Doctor: I own a 2008 Honda Civic Hybrid and its gas mileage is not what it should be. I have also kept records at highway speeds (65, 70, 75 mph) and the tachometer has the same rpm reading of about 2,100 rpm. The car has a CVT transmission and I suspect it is not shifting into high gear. I complained to Honda and they did not reply. John

Dear John: Gas mileage will vary under a number of conditions, including driving, weather and the area you live in. As for the engine speed being the same or very close to it at 60, 70, or 75 mph, the CVT transmission design is to keep the engine at its operating engine speed. If there was a mechanical or sensor problem, then the “check engine” light would illuminate.

Dear Doctor: I own a 1997 Volvo 850. The odometer and trip odometer stopped working, however the speedometer still works. The owner’s manual mentions a speed sensor. I understand the speedometer is electronic. What needs to be done to correct the odometer? Al

Dear Al: The problem is located in the dash cluster. The cluster will have to come out. You will need to either replace it with a used cluster (with whatever mileage is on the used cluster) or your cluster will need to be sent out for repair.

Dear Doctor: I own a 1989 GMC Sierra pickup truck. It runs fine until the engine gets warm, then it shuts off and won’t restart for up to five hours afterward. It is getting spark and gas. I changed the ignition module and it ran a little longer with the idle speeding up just before it shuts itself off. Any suggestions? Bill

Dear Bill: The first step is to check for trouble fault codes, as well as actual fuel pressure and volume. Both spark and fuel pressure are critical on fuel-injected engines. Weak spark and lack of fuel pressure are common faults on this vehicle. Distributor rust buildup is a common fault, too. I have also had some computer failures that will act up when warm. The key to finding the fault will lie on the use of the proper diagnostic equipment and qualified technician.

Dear Doctor: I own a 1979 Cadillac Seville with only 61,000 miles. I have difficulty starting the engine. I have to keep the gas pedal to the floor and it takes a long time to start. When it does start, the engine idles high for 15 minutes. I have replaced both the heat and coolant sensors, along with the TPS sensor. Do you have any suggestions? Joe

Dear Joe: Before replacing any parts or sensors, important information is needed from the computer and all sensors, including intake manifold, coolant temperature and fuel pressure. Fast idle speed faults can be from a faulty or dirty fast idle valve.

Dear Doctor: I own a 1997 Lincoln Town Car. I recently had the fuel pump replaced. Since then, the gas gauge does not register correctly. They said it would take about 50 miles for the gauge to register correctly. It has been a month and I cannot tell how much gas is in the tank. What are your thoughts? Louis

Dear Louis: The first step is to check the connections at the fuel sender. If the gauge worked before you changed the fuel pump, then the fault is most likely the fuel-level sensor, which in some cases is part of the fuel module assembly. I always recommend the use of a factory fuel-pump assembly.

Junior Damato is an ASE-certified master technician. E-mail questions to info@motormatters.biz or address them to Auto Doctor, 3 Court Circle, Lakeville, MA 02347.

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