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Hard, Brittle Plastics Breakdown, Cause Leaks, Issues

By Junior Damato, August 11th, 2012

strong>Dear Doctor: I own a 2006 Volkswagen Passat. The "check engine" light is setting a code for the front oxygen sensor as being stuck in a rich condition. My technician said the problem is just a faulty oxygen sensor, so I replaced it. The next day the "check engine" light came back on, indicating the same code. Do you have any ideas? Raymond

Manufacturer photo: 2006 Volkswagen Passat
Manufacturer photo: 2006 Volkswagen Passat

strong>Dear Raymond: I see a lot of four-cylinder Volkswagens with vacuum leak problems that will cause the "check engine" light to illuminate. VW, like many manufacturers, uses hard plastic tubing to connect several vacuum and evap devices. Over time these plastic tubes get hard, brittle, crack and leak. VW also uses a plastic valve on the front side of the valve cover and a metal tube that has a check valve for engine breathing that I have seen fail. This will cause a lean condition and the oxygen sensor to stay in a rich mode. The technician will check for a vacuum in the crankcase by removing the oil dipstick and checking to see how much vacuum there is. There should only be 1-inch of vacuum; any more indicates a vacuum problem causing the oxygen sensor to be stuck in a rich condition.

strong>Dear Doctor: I bought a 2012 Nissan Sentra three months ago. Once in a while I hear a "beep" but no lights or "check engine" light come on. My seat belt is buckled and all doors are shut. The dealer hooked it up to their laptop computer and found everything fine with the car. Have you heard of such a thing? JB

strong>Dear JB: Today's vehicles are loaded with electronics and noise makers, such as beepers for seat belt, key buzzer, parking brake and lights left on, door ajar reminders, etc, but there are no noise makers for the "check engine" light. Try leaving the lights on, seat belt unbuckled and the key in the "on" position with the engine off to determine if the sound comes on then. This could help the technician find the circuit that is causing the sound. You also may have to wait until the sound becomes more frequent.

strong>Dear Doctor: Recently, my 2007 Dodge Ram 1500 Quad Cab with 50,000 miles would not start. No sound, no crank, nothing, but all of the other electrics worked. The battery is six months old. I had it towed to the dealer and they replaced the starter, which I probably did not need. Two days later it wouldn't start. I waited an hour and it started. I returned it to the dealer where they had it for 4 days. Said they couldn?t find the problem as long as it was starting. They even let it run for an hour or so out in the 90 degree sun. It keeps starting. The mechanic did say the scan showed something but did not elaborate. They are stumped! Can you help me? Jeff

strong>Dear Jeff: Whenever I see a problem like this I check all of the connections. The next step is to suggest to the owner a tie-in of a small light into the (S) terminal at the starter, running the light by the windshield cowl so the driver can see the light when the key is turned to the start position. If the light comes on when the key is turned to the start position then power getting to the starter. If the test light does not light up then there is no power and it gives the technician a good indication to check the starter wire circuit. The use of a professional scan tool can also help if there are any fault codes. When you put the ignition key in the cylinder the Body Control Module has to recognize the key. You can also look at the security light in the dash cluster to see if it is flashing. This can also help the technician in diagnosing the condition.

strong>Dear Doctor: I own a 2003 Ford F-150 with a 4.6-liter V-8. Intermittently, the temperature gauge goes to hot, but there are no signs of the engine overheating. When I shut the engine off and restart it the temperature is normal. I have replaced the thermostat and cylinder head temperature sensor. The "check engine" light is also on. Do you have any ideas? Steve

strong>Dear Steve: I have also seen this problem happen to speedometers and tachometers due to faulty ignition coils. My first encounter with this problem took me to our friends at Identifix, and sure enough, there were other technicians who had run into these same conditions. The ignition coil specs are found on the Alldata web site. To verify and check the condition of ignition coils a professional scan tool that has the mode 6 option is needed, not just a scan tool reader. The faulty ignition coil spikes the computer and causes the problem -- and can also cause faulty readings on the speedometer and tachometer.

strong>Dear Doctor: Why aren't small SUV manufacturers making more cars with AWD and manual transmissions? Almost all manual transmissions have front wheel drive. I am told by the salespeople that they get asked that question everyday (but they don't know the answer). Susan

strong>Dear Susan: The majority of buyers of small all-wheel-drive vehicles do not want manual transmissions, plus the cost of a clutch replacement would be over $1,000. Today's automatic transmissions are now five speeds, and some up to eight speeds. Automatic transmissions offer great all-around performance and some have paddle shifters mounted to the steering wheels for a "manual shift feel." All of this comes without the hassle of shifting, especially in stop and go traffic.

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