06 BRM bad compression 2nd cylinder

I need to get some insight into a problem I have with an 06 Jetta BRM engine. I get 500psi compression on 1,3,4 cylinder and the 2nd one I get 250psi. The engine smokes a little bit at start up but it clears up quick. Cold idle is lumpy, warm idle is good, no misfire codes, but the Mes Block 13 shows the injector 2 deviation at 2.99 at idle, when reved up it comes to 1.xx range.

What could be wrong here? Engine has barely 50k miles.

Check cam lobes for wear. Also check for "puffing" blowby that is in sync with half engine rpm, ie, puffs whenever #2 fires.

Cam looks good. I don't belive cam wear can affect compression this much. I need to check the valves to see if they close tight or not, or maybe injector seals?

For injector seals to leak that much, there would be alot of compression getting into the fuel passages. I'd think it would run super sick even warmed up.

I agree the cam would not likely cause the compression to go that low, but it is free to check, so glad you did.

Do check the blowby. That is the test I use on troubleshooting larger diesels. Note that just taking the oil fill cap off is not going to tell you much, as it pulses there anyway. But normal pulsing is 2x per rev, bad rings on one hole will be 1 pulse per two revs.

still have a hard time understanding how your procedure works. can you tell how excatly you determine those pulses?

I would look at the cam lobes and follower for that cylinder anyway, and all of the others. Look in detail with a bright light, rolling the engine to see each lobe pointing up and aft, then each follower with lobe fully down.

In my experience, a BRM detailed cam inspection is never wasted.

In the last week I have seen 3 BRMs, all with holed lifters. One was getting PEAK airflow of about 400 mg/stroke.

One had #2 cylinder wall scratched, apparently from follower debris going through the oil system and catching in the rings.

The cams can wear very strangely. One lobe may be worn down so that the follower is being actuated by the injector lobe.

ok, here's the thing:

1st: put some oil down the glow plug hole into the cylinder and compression is back to normal.

2nd: swapped injectors 1 and 2 and started the engine. Engine runs smooth and good for now.

Drove the car for a while and after 1hr trip I get values to cyl2 back to 2.99. Engine runs a lot better than before.

Now I inspected the camshaft closely and see that cyl2 has the exhaust lobe scratched to the left, same thing with cyl4.

Question is why did the engine ran smooth and nice after swapped injectors, and after a while (half a day or driving) some lumpines comes back?

So, I determined that the low compression is mostly caused by flooding from the injector. now the questions is why does the computer keeps this injector opened so much more?

Check the area around the number 2 glow plug...could be cause of the compression leak and you will notice carbon on the threads or thread damage. Send out oil sample for analysis to determine if coolant is in oil indicating a head gasket leak/failure or high metal suggesting excessive ring wear.
If you baby this car take it out and run the hell out it. You could have carbon on the valve and running it hard has been suggested by other posters to improve the seating of the rings improving compression.