Questions and Answers
Passat Diesel
Q. I have a 1996 Volkswagen Passat with the 1.9 liter Diesel engine driven 75,000 miles. Manual 5-speed transmission, P/S, A/C no ABS.
For about two years now or since about 45,000 miles the engine has idled abnormally rough and there is, what seems to be a drive line vibration that starts at 2250 to 2300 RPM. At higher Revs. the vibration seems to abate. It doesn't seem to get any worse. I've had the car to the dealer several times in the past and they've told me "it isn't as bad as so and so's car." About a year ago they said the idle vibration was caused by engine mounts. After several hundred dollars for replacing the engine mounts the problem persisted.
Today I had the car to dealer for the 75,000 mile service and a new muffler. I also asked again to look into the rough idle problem and the 2300 RPM vibration. Today they had a new diagnosis. Why they did not find this earlier I don't know, but they said that the intake manifold was carboned-up and restricting air flow and would have to be cleaned. What causes carbon build-up in the intake manifold, and how can this be prevented in the future?
Do you think this is the cause of the rough idle and 2300 RPM vibration. The estimated cost to remove and clean the manifold is $475.00. They said that they send the manifold out to a machine shop and that they needed the car for five days. At this cost I need some assurance the problem will be fixed. I've already been through the cost of engine mounts.
Are there any VW bulletins on this problem and solution?
EugeneA. The only TSB I was able to find relating to this problem was a recall on the turbocharger. Some diesels came with turbochargers manufactured by the supplier "KKK". The affected turbocharger could have sustained damage due to lack of lubrication, if it was operated at high speed when the engine was first started up. VW decided that all "KKk" turbochargers be replaced with a "Garrett" turbocharger. This might be your problem. The 1996 model Passat TDI vehicles affected are within the following vehicle identification number range: WVW_ _ _3A_TE000001 to WVW_ _ _3A_TE130028. If you car falls within that range, it is something that should be checked into.
If this doesn't apply to your car then it becomes a little more complicated. Carbon buildup is normal for diesel engines since diesel fuel is not as finely refined as gasoline. There's really no way to prevent it, it happens. Usually it is not a problem. My diesel Mercedes has 216,000 miles on it with no carbon problems.
Could it be the cause of the problem? It is certainly a possibility although I would not rate it high on the possibility scale. The one thing about diesels is that there is not too much to affect their performance.
If their recommended repair does not fix the problem, then you may not, legally, be obligated to pay for it. I would suggest driving the car before paying the bill to make sure the problem is indeed fixed to your satisfaction.
Additional Information provided courtesy of ALLDATA
