Sure! I appreciate it.
Initial diagnosis and engine acquisition:
Customers vehicle came in, diagnosed by another shop that it needed a motor. After inspection, I see the timing chain tensioner failed; Ubiquitous standard failure, the brittle guide broke and the metal plunger caught and broke the timing chain. The car has 225k on it. I found a motor from a salvage yard with 78k, with turbo. Customer decides to go with this motor. After receiving the first motor, which looked like it was no where near as low as 78k, I performed a leak down test on it and it failed on two cylinders at nearly 100% leak down. The salvage yard took a week and finally sent me another motor. This motor looked great, although it was not a BWT, the sticker was missing. The yard said it was a BPG and that it was interchangeable, I ended up having to swap the injector harness from the original BWT motor to it so that everything hooked up to the vehicles harness. This engine leaked down acceptably for a motor that has been setting around for extended period.
Preparation and installation of engine:
I took what was left of the timing cover off the engine. I noticed that according to the timing cover and pulley I had on there that the crank:cam timing was off a couple teeth on the camshaft pulley. At the time I chalked this up to whatever accident the vehicle was in and the damage to the timing cover. So I installed the new timing belt, idlers, tensioners, belt, etc per the Mitchell1 directions. I don't recall which crank pulley and which timing case cover combination I used, but I swore I checked to make sure they were indexed at the same angles ( maybe not? ).
We then install the engine and when we fire it up its a little noisy at the cam tensioner area and a very rough idle that smooths out with increased engine speed. I scan it and it's complaining about the variable intake runner volume motor. I swap the old one of the blown motor and fixed that code but did not fix the rough idle. Meanwhile the noise in the cam timing chain area is getting much worse at idle and smooths out with increased engine speed. I also have a P0016 code, which I figure is due to the tensioner failure. I change the tensioner and cam timing change per directions on Mitchell1. This solves the timing chain rattle but does not solve the P0016. At this point I start looking at other metrics to see if anything else is going on. I check fuel pressure, it's delta(requested,actual) rail pressure is 800 at idle. I replace the HPFP and that fixes that problem; Still rough idle, P0016. Now I am racking my brain thinking what could possibly be wrong in the timing. I find a white paper from Audi about the variable timing system and realize there is a spring loaded piston that locks the phaser when not exposed to oil pressure, so that when it is timed, it is always timed correctly. Looking at the old phaser from the blown motor I see the little notch that I saw on the motor I was timing, which I recalled was pointing straight down. This notch is not mentioned anywhere in any technical articles or directions, i'm sure its for use when assembling the phaser itself. Anyway, it came obvious to me that I had timed the motor without the phaser being locked. So it was viola moment and I was sure I would pull that phaser off and it wouldnt be locked and I would have my problem. I pulled the valve cover and rear timing cover off and of course it was out of time by visual cam lobe inspection. So the phaser was not locked when I timed it last. This time I decided to take apart the phaser from the old motor (it has a chipped tooth), inspected it and learned how it worked. I then took apart the phaser from the new motor made sure everything was good and nothing was worn and retimed the engine. Still no fix....so I rack my brain and think maybe the problem is the crank sprocket or timing cover marks are out of angle. I pull #1 plug put a screwdriver in it and attempt to dwell tdc myself, granted this isn't a great test by yourself, it seemed good. *I would like to do this again with some help*. That's when I back probed the cam and crank sensors and verified they were actually out of time. Verified the waveforms independently were acceptable. Then I had a customer come that has the same vehicle, back-probed it and verified what I thought the correlated waveforms should look like.
So with a reasonable degree of certainty I know the vehicle is physically out of time. I just still don't know why or how. I really wonder if there was a reason why it was not timed to the marks I was using when I got it, coupled with my uncertainty of my tdc dwell test, makes me wonder there is something going on there.
Thoughts?
Reply With Quote
Originally Posted by borderm3
Bookmarks