1992-94 Audi Problems

car_hunter

I have a 92 Audi 100S. Everyday when I start the car in the morning, it starts rough (as if all parts are loose - sounds more like a weak rusted old diesel engine). Then in a few seconds when the RPM settles at around 800,, it gets a bit better but the noise (similar to a knock or a sticky valve lifter) is still there. I can also hear the noise go up a bit when I push the gas pedal. So today I showed it to someone who said that it was quite common in many V-engines. He said that it is probably a sticky valve lifter that needs some cleaning. He recommended an additive that cleans the valve lifters and makes them run smoother and quieter. He also suggested using a 10W40 grade engine oil for the V6 engine. He says that heavier oil will improve lubrication and reduce engine heating, but may reduce mileage. I don't remember the name of the additive he mentioned but I can ask him again. I will list the additive here once I find out. I did not find enough information on this car in the Town Hall and so I created a separate discussion. Hoping that Audi owners will list/share their problems here. Thanks.

Mr_Shiftright

No, I don't think you are getting the right advice here if indeed you have one of the early V-6 engines. The inline engines do have lazy lifters that take upwards of 15 seconds to bleed the air out after start-up, and an additive such as Swepco 502 (or was it 503?) will help.

But if you have the V-6 engine, there is a pressure relief valve in the head that goes bad and needs to be looked at. This will cause loss of oil pressure to the lifters.

Mr. Shiftright
Host

car_hunter

Shiftright, thanks for the response. I have the V6 engine. Even after driving for about 30 miles (one way to work), there is some noise and the engine is rough. I will check the pressure relief valve, but the oil pressure gauge on the dash shows real good pressure. Also, the car doesn't seem to have enough power. It is supposed to be a 172HP engine but runs like a 120HP. Not sure if I need spark plugs or a tune up. Not sure - any suggestions will help. Thanks.

Mr_Shiftright

Well, one problem at a time I guess. You could do a compression test just to see where the engine is at right now. I don't think the oil pressure relief valve will affect your basic oil pressure very much, as your sender is reading oil pressure at another point below the head.

car_hunter

I did show the car to another guy who works on import cars like Audi, Porsche, BMW, etc. He checked under the hood, test drove the car and suggested the following to fix the rough engine, valve lifter noise and lack of power:

- Complete tune up: spark plugs, cap, rotor and wires
- Replace valve lifter to fix the knocking engine noise

However, he does not believe that an engine oil additive would fix the valve lifter noise since the oil was changed only 800 miles ago and looks clean. The car is also driven daily to work which should free a sticky lifter. Anyway, if it helps I would like to try using an additive to save the repair cost of replacing the lifter (approx. $200 by his estimate). But I am not sure if an additive would help. Any suggestions/recommendations on additives?

Mr_Shiftright

I don't think that is good advice in your case. I think you should have that pressure relief valve looked at, as I called an Audi specialist for you and this is what he advised. This is a well-known issue with the early V-6s.

You have to remember, just because a person works on one type of German car, that does not mean he knows how to work on another.

First things first, the most obvious first and then work down to the more obscure.

car_hunter

Thanks, Shiftright. I will have the pressure relief valve looked at and will let you know if it was faulty.

Mr_Shiftright

Yes, that would be interesting to know. It may be something else, but since that is accessible and problematic, seems like a good first step to me.