VW Maintenance Reality Check

To All:

My son recently purchased a Nissen pick-up fitted with a modest but thoroughly modern 2.5L inline four cylinder fuel injected engine having variable valve timing and dual overhead cams actuating 16 valves. On a

900+ mile trip the vehicle averaged better than 25mpg.

As with all new vehicles sold in the States since 1996 the pick-up is fitted with version 2 of the On-Board Diagnostic system. (ie, OBD-II) This reflects the fact that like all modern internal combustion engines, its management is governed by a several embedded microprocessors, each dedicated to specific tasks. The electro-mechanical devices controlled by those computers, such as the fuel injectors and various actuators, as well as the numerous sensors monitored by the computers, are themselves embedded within the assembled engine, making manual diagnosis inconvenient if not impossible. Which is why we have an On-Board Diagnostic system. In effect, the system uses a computer to monitor itself. Should any part of the system fail it turns on a warning light and in most cases, falls back upon a less sophisticated method of control, allowing the vehicle to run well enough to make it back home.

By periodically interrogating the OBD system and creating an archive of the results you can see various components slowly degrade over time, allowing you to schedule their replacement well before any failure can occur. Of course, to do that you need to be able to connect to the on-board computer with a PC or lap-top running suitable software, which is commonly available. Some software facilitates this by linking parts procurement to the diagnostics, allowing you to place an order by simply right-clicking the mouse.

All of the information needed to diagnose and repair the vehicle is contained in the factory service manual, a two-volume set running to more than 1,600 pages which costs about $250. As with most modern-day vehicles(*), the pick-up has been designed to reduce the amount of time needed to swap-out those parts needing periodic replacement. Fasteners and adjustments have been located so that everything involved in a particular repair procedure is located within arms-reach of the mechanic.

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By comparison, in the mechanical sense an air cooled Volkswagen is about as complicated as a two-cell flashlight, with all of the Preventative Maintenance items clearly spelled out in the Owner's Manual and/or the Factory Service Manual. But when something finally wears out -- when repairs are finally needed -- the only diagnostic computer is the one between the mechanic's ears.

-Bob Hoover

Reply to
veeduber
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Bob,

This is a project I have been dabbling in for some time with my 1997 Kia. The Davis Instrument "Car Chip E/X" can retreive all four types of OBD-II diagnostic codes and monitor up to 4 sensors at a time. The nice part is that the car chip is about the size of a box of matches and can remain attached to the OBD-II connector, logging data in 5 second intervals that can be pulled out into a desktop or laptop when it is convenient, rather than lugging around a laptop for constant monitoring.

Ideally to get the best results one would start with a new car, take readings from day one of all the sensors, and repeat as necessary to see over time what sensors are drifting out of tolerance. The other thing to consider is the replacement interval that is specified for things like O2 sensors and MAF sensors, which from what I've researched are usually spec'd out at 100,000 miles MTBF.

Getting back on topic, I still like driving my VW because of simplicity and the number of "Point and stare" people you see now that the aircooled VW is an antique. However, fuel injection, air conditioning, heat, cruise control and all those other features of 'modern cars' do make life a hell of a lot more comfortable on a long trip or the daily commute ;-)

Regards,

Chris

Reply to
halatos

Yup, that CarChip is a nice tool -- I maintain all my own cars so have one out of necessity. It is presently in my in-laws Altima.

Their Altima had been stalling for some reason at random. It would become hard to start and then drive fine again -- all without rhyme or reason. It would turn the light on the dash on from time to time.

The Nissan tool (both the actual scan tool and the guy working on that car - I use the word interchangeable in this discussion) diagnosed the problem and felt it was necessary to replace the crank sensor, some secondary o2 sensor and some other sensor. This was in two dealer visits, neither fixing the intermittent problem -- all because a particular random code was thrown.

After the third time of visiting the dealership, the manager mentioned that they'll need a new computer ($1100 + installation). He mentioned that the ECM must be the cause of all the problems because none of the stuff they've been replacing makes any sense. He suggested it might be related to a stopped up AC drain hose. Mind you, he did not suggest giving them their money back ($900) for the other randomly performed service.

$1100 is a lot for retirees so they drove it back home, not getting it serviced. I just found it hard to believe it was the ECM. After some probing around with a DVM, found a bad ground connection to the battery and one to the ECM. Fixed the connections and the car has been running fine since (but still have the carchip recording stuff, just in case).

So Bob's absolutely right. I like technology, but learned to never trust it implicitly. There's no better computer than the one between your ears. Too bad the Nissan tools don't know that..

Remco

Reply to
Remco

I much prefer the simple, less complicated engine compartments as in my VW bug, benz 240D and 300SD than my C5 corvette. Love those purely mechanical engines. I absolutely hate the plastic covers that encasulate new car engines, as if it is a hands off approach to car ownership.

snipped-for-privacy@isp.com wrote:

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Reply to
robrjt

Damn, that's discouraging. Guess I'll stick to oil lamps.

Reply to
j

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