MAAllroad

Anyone have experience with a 4.2 jump timing? Dealer is diagnosing mine with one at 116K miles. Notes from dealer are below.

Dealer has scanned the ECM for codes and found that cylinders 1-4were misfiring. There is also a “popping” sound in the intake. They pulled off a vacuum line and checked manifold vacuum, it was low (about 10”) and it fluctuated with the popping noises. This is indicative of improper valve timing.

sb_gli

Or it could just be a large vacuum leak. I'd check that first.

GTA_Driver

The 4.2 can jump timing if the rear chain loosens or skips. However, you would have a poorly running car. What are the symptoms?

Is there any rattling noise from the back of the engine?

Need more diagnosis, including compression test, before shelling out $4K + to the dealer for repairs.

ProtoFly

Welcome to 4.2 timing chain guide issues. There are a few S4 owners that have been having this issue, I expect, due to mileage. I'm having the issue with my 2005 A6 4.2.

It begins with the startup rattle, which I believe is a symptom. The rattle is claimed to be 'normal', but I'm not so sure. My 4.2 did the rattle for about a year, then one day I felt a 'bump' from the engine, and cylinders 5-8 report multiple misfires. Ran good part-full throttle, but idle no good.

Doing a bunch of research, and I diagnosed it down to a failed timing chain guide. I'm in the middle of the job now, which did require the engine and transmission to be removed, since the chain system is in the back of the engine.

Depending on how far yours has jumped time, you -may- have internal engine damage, from valves hitting pistons. Hopefully not. Mine did not grenade itself as far as I can tell, as evidenced by the smooth running on throttle.

Parts will run you about 2k for a complete job. ECS Tuning is offering 'kits' now. You -may- also need the mechanical cam adjusters, which wear out. Here's a link to a post on this in the A6 forum:

https://www.audiworld.com/forums/sho....php?t=2814298