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Well I wasn't expecting this! Pics...


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Just helped out someone over the WE with their rough running tdi, having come to me after spending over £500 with vdubs, who didn't diagnose it right! I said I'd be happy to stand up in court to tell them them what i thought of their 'professional' skill level. Huh! They changed the EGR valve. Wrong! I reckon @Rich, @Blue Loop, @Skajme or @RAB would be able to diagnose it in under 5 seconds. Took me about 30...

Symptoms were obviously misfiring, running on only two cyls. until warmed up. Started ok, and had a loud tapping noise- really loud with the air inlet duct removed. VCDS showed a big injection quantity imbalance between cylinders at idle- trying to add fuel to cyl 1 and pull from 2 & 3. Obviously air starved on no.1 with the inlet valve not fully opening. It's amazing how vdub ECUs actually measure the rotation time between injection pulses and trim the injection timing to achieve a smooth idle. When a power stroke has more push than the other cyls, it obviously takes less time to rotate. So it adds fuel to the weaker cylinder and pulls from the others to try and even out the power strokes. Neat idea.

This 2001 Lupo had 165k miles on it, with a decent history... Down to the breakers yard to grab a camshaft (and a tappet) from a 9N Polo, which was pretty much like new still. It always seems to be the lobe next to the pulley that goes, having seen a few worn cams at the breakers. The engine is at a slight angle, with the gearbox end being slightly lower.

Straight forward job- just loosen the timing belt and tensioner. Pop off the valve cover and bearing caps. Pull the dodgy tappet. Pop off the pulley, swap over everything and back together again. You don't even need to remove the high pressure fuel pump or adjust the injection timing as everything is precision made.

 

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I threw my old cam in the scrap car the other day and the traditional concave lifter/set.

Still runs like **** on idle after changing it

 

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I still wonder why the balance shaft and that wierd chain setup is there. The 3 cyl engines run just as rough without the balance shaft apparently (german lupo forum experiments). I discovered that you can tweak the idle slightly by messing with the injector lash adjusters. The rule is screw in to screw locking at max injection depth then back off 1/2 a turn. If vcds says an injector is chucking too much fuel in, i've found that backing off a bit more, like 3/4 turn does reduce the injection quantity very slightly. 👍🏻

On that concave and holed tappet, the oil must have been flooding out. I reckon not long until total catastrophic failure and game over there. Every car should have a magnetic sump plug like @CLAYTONJONES uses. Would certainly have been an early indicator that something was wrong.

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There was a lot of silver floating about my engine but I did catch it before the hole appeared.

Tbh I could do with an injector loom.

Mine used to run nicely too.

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Yeah what got me is that the guys in vdub completely missed it. I mean come on, how can you miss a really loud tapping and think that it's a clogged/stuck/broken EGR valve. The guy who runs that car is not happy about it especially after I told him that there was probably nought wrong with the old EGR valve. Get rid and chip it... 👍🏻 More power. Blow the thing up properly. An AMF may as well have an exciting end of life rather than just wither and die with a duff cam or chain.

The old injector loom is probably fine. Just crack all the brown plug covers off, squeeze the little spade terminal plugs a bit, so they're a tighter fit and whack 'em back in one by one. Will last forever. I did that to a Polo a while back and haven't heard a squeak since. Stupid bad design that loom wiring. 3mm spades are designed to take up to about 3-4A. The injector coils can sink over 20A... Mmmm.

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That was an interesting read! Good to know the forum knows more than others but bad to know the expert who charges eye watering amounts don’t! 

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That's why it's important to run with the correct grade of oil with a Tdi. The injectors put an enormous amount of pressure on the camshaft. If you don't change the oil at the required intervals (and/or use an incorrect oil), you'll get lots of wear on camshaft shell, particularly the upper ones. That's what has happened here. Even if you do the correct thing, you still get wear!

RAB

 

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