Dan [Sac]

Back story -

Bought the car not running (dead battery) with coolant leak(s).

Replaced battery, car started with some difficulty, but once it fired it ran smooth. Located water leak and fixed (plastic elbow near driver side EGR at the firewall).

Cold compression test showed 130-160 on all 6. Changed the gauge cluster (dead pixels in message center).

Restarted car again, small coolant leak at the front - water pump time. Changed water pump, timing belt (by the book), overflow reservoir (threads on cap were stripped) radiator (leak at end tank on driver side), fan blade (cracks at base of some blades). Replaced spark plugs with OEM-recommended NGK coppers (BKR6E @ 0.032" gap)

Fired right up, smooth idle.

Drove about 8 miles with no issues, car behaved great. Good power even through the automatic transmission.....and then suddenly started having ignition knock/misfires. Very poor idle and low power under 2000 rpm under more than 10% load. Freeway driving at cruise seemed normal.

CEL comes one - codes are for: Random misfire, cyl 1, 2, 6 misfire. No other codes. Reset codes, change coil pack, same issues, still random misfire code, and cyl 1, 4, 6 misfire this time.

Check for spark - have strong spark in all 6. Change fuel filter, even fuel pump to be sure as current one doesn't seem to prime audibly. Car gets harder and harder to start. Finally it doesn't start at all, just cranks. Still have spark, still have fuel. Changed both coolant temp sensors. Same. Changed entire PCV system with new (except for suction pump). Same. No codes set during crank/no start.

Take it apart, timing is spot on. Valve covers off, cams are timed perfectly. CCTs (including plastic shoes on both sides) are intact. Chain link count is good.

Cleaned MAF with proper solution, cleaned TB and its elbow, checked it thoroughly for cracks/leaks and it checked out ok. Replaced all vacuum lines with fresh supple rubber.

Still no start. There are probably more things i've tried that I've forgotten, but at this time I am ready to either part the car out or just sell it as a mechanic's special.

Ideas/suggestions?

Prospeeder

Well. Engine computer is always possible, no faults? You have to rule out everything else and then turn to that. The engine computers ground is on the firewall by the coolant tank, I had a Passat that did almost exactly that, took off the ground, looked alright, but i scrubbed it with a brush, took the nut, got all the pant off the bottom, re tightened the ground, cleaned off the fouled plugs and it started with some cranking. 2.8s seem to like to flood out real easy.

41v

try spraying starting fluid? see if it makes any difference

use a noid light to check the injectors are getting a signal

use ohm meter and check each injector for continuity/ohms maybe a few are bad

just a guess- replace crankshaft position sensor

Dan [Sac]

Found the culprit, it's the piston rings.

Since I've done the valve cover gaskets and removed most of the oil out of the cylinders the compression dropped to 60-70 in cylinders 1, 2, 4 and 6. Adding a tablespoon of oil and redoing compression sees them go back up to 100. With oil in the cylinders it finally did start, but running on 2 cylinders only. Once the oil burned up it was back to no start. She's going to need some lovin'.

Prospeeder

These engines will flood and loose compression very easily. Keep trying, keep cleaning the plugs off, foot to the floor cranking, It should eventually come to life and just hold it at high rpms until it clears out and will run ok at idle. I see this several times each winter. Odd for it to happen in summer but still possible. The rings are not just going to go bad sorry. But with no oil film on the cylinder walls and washed out rings it will drop compression and not run.

turbo510

You must have really dumped a lot of gas into those cylinders to loose that much compression. Did you scan with VAG-COM or a generic OBD tool? It might be helpful to see what the ECU receives from your new coolant temp sensor. It's possible that the ECU is reacting to an incorrect signal, and overloading the engine with fuel. Check the plugs after a start attempt; are they wet or black with soot? The only time that I've had starting problems with my 2.8, which is almost never, was due to the ECU being told the coolant temp was -50C, on a +20 day. In that case it was the CTS.