Customer Vehicle: This article is about a 2006 Audi A4 with the 1.8L Turbocharged engine. Customer complaint: The vehicle had the check engine light on. Diagnosis: We verified the complaint, test drove the vehicle and there was a noticeable lack of power. After much testing and diagnosis we decided to check how much crank case vacuum we had. See the video of us testing the crank case pressure - To test the crank case vacuum we wrapped the end of the hose for the pressure tester with electrical tape till it would seal in the oil dipstick tube. Then we ran the car and found we had about 11 inHg of vacuum at idle and when we power braked it, we had about 1-2 psi of boost pressure in the crank case. Side note - A normal production car should measure about 1-2 inHg of vacuum in the crank case while running at idle. There should also be no boost pressure in the crank case for a normal production car. Another interesting side note - During our initial visual inspection we had noticed that the engine was leaking oil from almost every seal on the engine. Having boost pressure behind oil seals that are not designed for pressure will cause them to leak. There are other things like bad rings that can cause boost pressure to get into the crank case but since we had such a high vacuum being pulled we suspected this had something to do with the PCV system such as a valve somewhere failing and allowing the intake vacuum or boost to reach the crank case. It turns out the pcv system on this Audi is very complicated and involves like 5 or 6 different valves for boost and vacuum and like 6 to 10 pieces of hose with everything is tucked in the engine bay real tight, so some parts are hard to see. Upon closer inspection and some disassembly, we found the PCV system had been tampered with. At some point one of the PCV valves with a T-fitting and had been JB Welded a piece of white plastic water pipe in place of a fitting that goes into the crank case. This was not a factory repair. Several other hoses were replaced with flimsy rubber hose, like a garden hose, that had collapsed in tight spaces. This was all hidden under the intake plenum, so it could not be seen unless some parts were removed for access. A side note on documentation - complicated systems like the Audi PCV system are lacking proper documentation in the aftermarket world. We had to check several different sources before we could find accurate PCV system routing diagrams for this particular vehicle. Solution and Verify the solution: We ended up replacing all the non-standard or broken parts and hoses, test drove the vehicle and everything was working as expected now.
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AuthorWalker Crystal Archives
May 2019
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