ProtoFly

2005 4.2, while driving to church on Sunday, I felt what could be described as a 'bump' - almost like a bump in the road, but the road was smooth. Immediately, I knew the engine was not running properly, and a few moments later, flashing engine light. Nursed it to church and home, running very rough, shaking badly at idle.

I don't see/hear any vacuum leaks, and the 'bump' and with the small rattle on startup that it has had (plus mileage), and I'm thinking that perhaps a tensioner just went and threw a bit of plastic into the chain, and now one bank is out of whack.

I cross posted this to the 4.2 engine forum, hoping for some other ideas, but if anyone has suggestions on where to start, I'd be very thankful.

Here's a partial scan from VCDS with the tasty bits:

VIN: WAUDL74F15NXXXXXX Mileage: 265760km/165135miles

Address 01: Engine Labels: None
Part No SW: 4F0 910 560 A HW: 4F0 907 559
Component: 4.2L V8/5V G 0010
Revision: -------- Serial number:
Coding: 0007772
Shop #: WSC 02335 785 00200
VCID: 2045F75CF3C6B41801C

9 Faults Found:
18061 - Please check DTC Memory of ABS Controller
P1653 - 008 - - Intermittent
18061 - Please check DTC Memory of ABS Controller
P1653 - 008 - - Intermittent
17538 - Fuel Trim; Bank 2 (Mult)
P1130 - 001 - System too Lean
16558 - Fuel Trim; Bank 2
P0174 - 001 - System Too Lean
16684 - Random/Multiple Cylinder Misfire Detected
P0300 - 001 - - MIL ON
16685 - Cylinder 1
P0301 - 001 - Misfire Detected - MIL ON
16687 - Cylinder 3
P0303 - 001 - Misfire Detected - MIL ON
16686 - Cylinder 2
P0302 - 001 - Misfire Detected - MIL ON
16688 - Cylinder 4
P0304 - 001 - Misfire Detected - MIL ON
Readiness: 0000 0000

KevinGary

Coil packs

newa6er

I agree with the busted tensioner or the chain jumped a gear

ProtoFly

Yeah, gotta admit that's what I was thinking too, except that when I read the codes, and saw the lean condition, and one whole bank misfiring, my thought is that the likelihood of 4 coil packs failing simultaneously is very small.

My gut is telling me that I'm looking at the chains/tensioners, and resealing the engine (which it needed anyway).

However, I'm also thinking that it could potentially be a secondary air valve for that bank, given the lean condition.

Ordering up the Bentley service manual <sigh>.

ProtoFly

Do you know (or anyone know for that matter) if there's a way to tell via VCDS whether the timing is off left to right on the engine? Obviously, pulling the engine, changing all the timing chains and guides and tensioners isn't exactly a small job, and then putting all back together to find the same issue, well, lets just say it wouldn't be the -best- day of my life...

newa6er

This has not happened to me so I am no expert. I have read many posts about this topic, one post suggests the VAGCOM will tell you if the engine CPU is compensating for the timing being way off. You'll have to search through the many "stretched timing chain and broken chain tensioner" threads. Or maybe you could figure it out yourself. Good Luck, I hope I'm wrong and it's something small.

BTW, how long have you had the start up rattle?

ProtoFly

The rattle has been there since I purchased the car, which was at 127000 miles. Seems to have gotten worse just recently. (another reason I suspect tensioner issue)

Nightlifephantom

Did you ever find a solution to this?

KevinGary

I think he sold the car. He is not an active participant on the forum.

ProtoFly

If the question was for me, then the answer is yes. I still have the car. It now has 202,000 miles on it. The problem was the passenger side upper chain tensioner, which had shed its plastic chain guide, which then promptly went into the exhaust cam sprocket, which jumped a tooth, causing the misfire and timing problem. This is unfortunately a common failure with this engine, which was used on the S4, C6, All-Road and A8 in that timeframe.

I pulled the engine, did a complete valve job, new tensioners and guides (updated parts), and the engine has been running great. Still burns a quart every 1500-2000 miles, but whatever. It hasn't gotten worse.

I have a failed AC compressor now, which I'll be tending to shortly. It's another typical failure on these and the S4, and much like anything else on this car, getting to the part to replace it is the majority of the work.

Yeah, I still love the car, despite its numerous flaws. The 4.2 sounds fantastic when you get on it a bit!