mkiv_tdi

Hi all, just bought a "new to me" Audi A8 from an old coworker for mine.

Some quick background: 127k miles. Well optioned. Coworker was looking to dump the car as he was tired of putting money into it. I've got VCDS so I figured, why not?

The engine and tranny seemed stout, and it drove okay minus a million lights and beeps on the dash for Electronic Parking Brake, TPMS, ABS, ESP, etc.

There were too many voltage errors in almost every module of the car for there to actually be a real problem from each of them. There had to be a main culprit...

The first problem to tackle on the car was a faulty rear-right brake caliper. The motor in the caliper was sucking the car battery dry all the time. The guy had to drive around with a juice pack in cause he would have to jump the car all the time.

$200 dollars later on EBAY for a rear caliper, a new battery, and a new Parking Brake Switch in the console fixed a large percentage of my problems. After driving the car for a day and clearing all of the codes and doing adaption for the back calipers, all of my various little voltage codes went away. No more beeps, no more lights, TPMS was recoded to the correct frequency and worked wonderfully.

Things were looking good! I saw from his documentation that a local audi dealer did the timing belt at 80K so I was relieved at that...

The only thing I decided to do was Valve Cover Gaskets and Sparkplugs. Straightforward, right?


Well in taking the VCGs off, I didn't like what I saw. The oil obviously wasn't maintained as religiously as claimed (or the shop totally ripped him off and never changed the oil) as it was sludgy and clumpy and had hardened into some corners of the head. I tried to delicately clean it, and went ahead with the valve cover gaskets and plugs.

Immediately after that, since I was still in the garage, I changed the oil and filter.

The car drove fine on the test drive afterwards, with no engine codes and no issues. Then I parked it and it sat for a week while I was away on business.

Fast-forward to the weekend, and I start the car after putting its new plates on... and two seconds after starting, CHECK ENGINE LIGHT.

Pull out the VagCom.

17748 - Camshaft Position Sensor (G40) / Engine Speed Sensor (G28)
P1340 - 001 - Incor. Correlation - MIL ON

17983 - Right Engine Mount Solenoid Valve (N145)
P1575 - 001 - Short to Plus - Intermittent


Hm, weird.

First thing I checked was the Camshaft Sensor. Went and bought a new bosch unit, replaced it in a few minutes. Cleared the code, turned car on... within 2 seconds same CEL came back on.

Okay... next step was to make sure timing wasn't off. Grabbed my blauparts 4.2 camshaft locking bar, put it on, checked all marks. Timing looked good at the crank.

Next was VAGCOM to check basic settings 091, 092, 093 on the cam adjusters. All between zero to 1 degree. Well within norm.


What in the world could have happened, and is the Valve cover job a culprit somehow, or is it just coincidence?


Thoughts? I'm going to take the VCG's off tonight.

dvs_dave

You haven't mentioned anything to do with the crank position sensor which was the other source of error? Maybe it's on the way out too?

Also, when you had the valve covers off you said it was sludged up and ugly in there. Did you perhaps do anything to the timing adjustment system (the chain drives between cams) whilst cleaning it up and they are now perhaps not working right, or maybe some dislodged debris is affecting their performance somehow?

mkiv_tdi

Hi Dave, thanks for the quick post!

I didn't address anything with the "CRANK Position Sensor" because I didn't get any codes for that.

The code I got was specific to the Camshaft Position Sensor, so that's what I changed out.

Yes, the valve covers were sludged up, so could the following be a realistic scenario?


Could I have stirred up some sludge while doing the VCG, and the subsequent drive after doing the job could have dislodged some of that and caused it to stick somewhere in the head? At this point, I'm taking the valvecovers off again anyway to make sure my camshaft marks timing marks line up.

But they should alight, right? Since my VAGCOM showed the cam timing on both banks to be at 0 degrees?

I'm leaning towards the cam chain tensioners, and I've already ordered the cam chain tensioner tool in anticipation of this weekend.

Junius

From a wild shot in the dark, it seems as if the oil sludge had somehow messed with the variable valve timing tensioner that each bank has, possibly causing the CEL. Are you sure it is the correct sensor? Are you sure it is plugged in all the way?

mkiv_tdi

Not sure how to edit my post. I'm usally on VWVortex and TDIClub and other forums.

Anyway, is the Speed Sensor the Crankshaft Position sensor that you were referring to, Dave?

If so, no, I didn't look at that at all. Would you happen to know it's location on the D3 A8?

mkiv_tdi

Here's some pictures that I took when I first opened up the Driver's side valvecover.
The pass side was the same.





The back of the valvcover was also caked in sludge that had to be scraped off with a plastic squeegee and liberal amounts of carbcleaner.

GradecEngineering

If your theory was correct, you would get codes for incorrect timing. Your P1340 code refers to a fault within the cam sensor itself, along with it's wiring harness all the way to the ECU. If it remains a hard code, I would probe the harness for a short or open.

mishar

Your engine is actually quite clean for 127K miles.

Check Engine Speed Sensor. It is bolted into the bottom of the gearbox in the flywheel area.

Jack88

Took the words out of my mouth.

You say you used carb cleaner to get the gunk? I'll be honest, I have no idea how that would interact with everything in there, but given it is designed to break down things, I would avoid spraying that stuff directly into the engine. Onto the valve cover while it's off, sure.

mkiv_tdi

I should have clarified a bit. I didn't spray carb cleaner all over the cams and into the head. Instead I used a rag that was dampened with carb cleaner, and wiped/dabbed anything big.

The valvecover was thoroughly cleaned and sprayed down as it was really clumpy and baked.

I'm surprised to hear that it isn't in that bad a shape.... That's encouraging!


So, Mishar, thanks! I'll do that later today. You wouldn't happen to have a picture, would you?
Either way, I'll get under it and take a look.

Gradec, my uncle is a MB mechanic for 30 years and he's the one that wants to take the covers off again and go headfirst into the cam chain tensioners.

I keep telling him that I didn't think that needed to be done yet.
Is my code referring to the bank on the PASSENGER SIDE of the engine?

That's the one that we swapped the new sensor onto. Should I have also swapped the driver's side camshaft sensor, too?

Other interesting notes that might be relevant:

1. During the valvecover gasket, I seemed to have pinched some of the harness leading out of the coil pack loom down alongside the engine toward the engine mount/motor mount and oil lever sender unit. I don't think any part of that harness should interfere with my camshaft sensor, and I made sure to fix/resolder/shrinkwrap the wires that were exposed.

2. I measured the female plug that goes into the camshaft sensor. It gets power as expected. 5v I think it was?

3. There have been a few instances that I've touched the engine and have been "shocked". Not a static shock, but a proper jolt. Also happened to my brother while he was helping me. Both times with the engine running.

4. Camshaft adjuster solenoids? Can those be checked without removing the valvecovers?

Both of these issues occurred after the valve cover gasket job.