Tune-ups, new parts can improve performance

Friday, December 5, 2008

Dear Auto Doctor: My 1992 Oldsmobile was running quite well, but at standstill a little vibration was felt on the steering wheel, so I replaced the VCR valve and it cleared up for a while. Since everyone talks tune-up, I got new plugs, wires, gas filter and the now the car runs fine, but at idle a little roughness is still felt on the steering wheel. I do get a 43 Knock sensor light but it always goes out and three mechanics said leave it alone. What could be causing the slight roughness at idle?

— George

Dear George: Tune-up replacement of worn parts should always help with fuel economy and engine performance. Rough idle usually indicates a cylinder is not contributing to the engine. It can be anything from an internal compression problem to a vacuum leak, leaking hose gasket or EGR valve, dirty fuel injector, or weak spark. A qualified technician will need to perform an engine performance and cylinder balance test and find the source of the engine problem. As for the trouble fault code, a pinpoint test of the system and a look on both alldata.com and identifix.com with subscription will guide the technician to the problem.

Dear Auto Doctor: I bought a used Mini Cooper with 40,000 miles and it’s still under warranty. Occasionally, when slowing from about 30 mph the car hesitates and there is no acceleration for a second or so. My dealer said the computer shows nothing wrong. What could it be? I’m afraid of pulling into traffic and having that pause.

— Bill

Dear Bill: There are no bulletins on this issue to date. When I get a vehicle with this complaint I hook up a scan tool and fuel pressure tester and take it for a road test. I will observe both scan tool information and fuel pressure. As soon as the engine acts up, I push of the record button and the computer information is recorded onto the scan tool. The next step is to compare recorded data information with known good information on that vehicle.

Dear Auto Doctor: I own a 1997 Buick Century with 75,000 miles. When the “check engine” light came on I took it to the dealer. They checked the computer code to a p01655 evap purge control solenoid circuit fault. The dealer replaced the solenoid and re-flashed the all computers. The trouble code came back. What do you think the problem could be?

— Bob

Dear Bob: I see problems like this every day. Just because there is a fault code for the solenoid circuit, does not mean the solenoid is at fault. The problem can be a simple with connection anywhere in the circuit computer or resistance in the wire harness. Electrical circuits need to be tested under real working conditions with a load on them.

Dear Auto Doctor: I am a smoker and the car’s lighter is a convenience that I like. The left cylinder that the lighter fits into will not work on my car. I have a replacement but I cannot get the broken one out. Is there a special tool that I should use?

— Denny

Dear Denny: There are no special tools to remove broken cigarette lighters. I suggest you bring the car to a shop so they can remove the cigarette lighter fuse with needle nose pliers, or whatever tool is needed to remove the lighter. Many auto parts stores sell multiple lighter receptacles that are easy to install and mount at the bottom of the dash.

Dear Auto Doctor: I own a very low-mileage 1995 Buick Park Avenue with only 52,000 miles. Last week the battery went dead, so we had it replaced. Since that day the gas gauge is down below the empty reading. Would the battery going dead cause this problem?

— Jean

Dear Jean: The battery problem should not in any way effect the gas gauge. The technician will need to isolate the problem by checking the fuel gauge circuit. Your 1995 car may have 1996 OBDII diagnostic capabilities. If so, then a simple test with the Tech 2 scan tool will be able to read the signal coming from the fuel sender to the computer and then to the dash gauge. If the car does not have 1996 OBDII diagnostics, then the technician will need to use a digital volt ohm meter. This will determine where the fault lies.

• Junior Damato is an ASE-certified Master Technician. E-mail questions to info@motormatters.biz. Mail questions to: Auto Doctor, 3 Court Circle, Lakeville, MA 02347. Listen to Junior online at www.1460wxbr.com Saturdays from 7 to 10 a.m. Eastern time.