strokestroke

Driving my Boss of Bosses to lunch in my 98 Audi A4 Quattro w/2.8 manual. Motor running great. Then I lost power, starts making loud tapping noises, stalls and is VERY hard to start.
You can start it, but only with throttle wide open and it runs rough. Oils good, coolants good (it was just after startup).

Feels like a vehicle that has off timing, timing belts look fine. Motor is quite hard to turn over, makes me think it's some kind of seizure. Over 300k on motor.

Any thoughts?

strokestroke

Oh yeah we ended up walking, Audi had to be towed.

cheeba

Ouch! I hope that walk was an opportunity to impress your boss with your awesomeness, and not just extra time to lament your busted-*** ride inconveniencing him

Obviously I can't be sure, but it does sound like a major mechanical failure in you engine. I'd think timing skipped, you dropped a valve, or a spun bearing. Maybe even a broken piston or rod if you were driving hard enough at the time of failure. That said, it could be someone like the tensioner failing and letting the timing skip a couple of teeth; which, might not be such a major problem. I would definitely not start the engine again - or even turn it over - you may have destroyed it by doing that. It's best to determine what the failure is before you try cranking any engine over, and even then, crank it by hand first.

Good luck - hopefully it's just some bent valves and you can toss a new head on!

strokestroke

I'm going to give this thing one chance - I recently bought it in rough shape and have sunk a lot of $ into it (coilovers, new rad, cv joints among others).
I had a budget for aftermarket rims - if I can't fix this for say 800 then you will see it for sale here as a parts car!

strokestroke

Update:
I popped off both valve covers. On the driver side, when the engine gets rotated by hand the hydraulic (?) cam-chain tensioner goes up and down, occasionally with a "clunk", and the chain gets loose, then tight.

The other side seems fine. Plugs were a little dirty, but from what I can tell there is no contact between piston and valve, which is what I was certain was happening when I broke down.

Does the cam sprockets look to be in the right spot here? (TDC)

strokestroke

Interwebz research indicate driverside timing off by a tooth or 2? How this happen? I'm not going to fix if there is valvetrain damage.

strokestroke

Compression 1-3: 150-170. Compression 4-6: 0.

Timing belt tensioner (2 bolt) seized. Gave it a quick rebuild, could not compress it before. Needs a new oil seal above the plunger.

The exhaust cam must have skipped. With all plugs out, when turning the motor over there really appears to be no contact. Is this even possible? I'm used to old Toyota 16v motors, zero-interference. . .

cheeba

I strongly recommend not rebuilding the hydraulic tensioner! They're prone to failure as-is, so unless you know what you're doing, i.e., an engineer and/or machinist, just spring for a new one. Or better yet, convert it to a manual tensioner

The engine is interference - looks like you bent the valves on the one head

K04-S4

Your picture shows timing is out as you have already determined. Agreed with Cheeba as there is no reliable rebuild of the TB Belt Tensioner, meaning best to install a compelte Timing Belt Kit with all rollers, water pump, tensioner & belt and ideally new coolant.

You may be able to *simply* replace Bank 2 cylinder head. I once bought a broken B5 A4 with same issue and found a rebuilt head for $500, installed it with TB Kit and good to go.

strokestroke

Dam it, looks like I'm going to fix it! Timing belt kit and head gasket kit - Blauparts or ECS Tuning? I want the one with the timing belt tensioner of course.
Sourced a used head with chain tensioner, valves, here we go. . .