Injector lash adjustment... to correct poor IQ readings?

Hi all,

06 Jetta BRM with 149k miles.

I just installed a Stage 3 Colt cam. I was under the impression that adjusting the injector lash was not necessary when swapping cams, so I didn't. Due to ignorance I never checked the injector quantity block with the old cam but now in VCDS it shows cyls #1 and #3 are within spec (with #3 being just a few hundredths off of zero) and #'s 2 and 4 are waaay off. Something like +1.8 and -1. Yes, rockers were installed in their prior positions.

I've read that when one injector is off, it's counterpart (2 with 4 or vice versa, in my case) will show compensation behavior. Dunno much about this, but anyhow, can this type of off reading be corrected by adjusting the lash? I've read posts by folks that adjust lash as per Bentley only to find their numbers worsen. I'm guessing that I shouldn't have to touch #'s 1 and 3 in my case, right? (Although I'm considering carefully marking the current position of #1 or #3 and then seeing how far from bottom it is, to use as a baseline for the others and contrast that to the Bentley spec in case they differ.) Also, I've seen many posts by folks that used Diesel Purge and posted their before and after IQ figures, but the differences have never amounted to that much, certainly not something as off as my #2 and 4 are, but I could definitely be wrong about that. So whaddya think?

Car is driving MANY times better than before my cam swap, I just want to fine tune everything now. The thing is, performance was so poor prior to the new cam and actuator that I have long ago forgotten what "right" is. Only overt thing I see is that it stutters/misses a bit when I rev past 2k and let go of the throttle abruptly. Does this no matter what I set for torsion (left it at 1.0 for now, since 0.5 eluded me) and the new actuator is just a quarter turn of the stop screw away from being spot on.

In short:
1- Are these IQ numbers possibly just due to lash?
2- If no, what should I do about the IQ? Or else what can happen?

Thanks!

I cannot answer your question definitively regarding lash vs. IQ change. However, it makes zero sense to me to skip resetting lash with a cam change. The injector lobes on the cam are a major component to the injection system. I always reset lash. To not do so is like replacing a crankshaft and not checking piston protrusion after, why would anyone do that?

If done at the proper time in the cam R&R sequence, lash adjustment takes only 5-10 min. I say do the basics of the job first, then try to figure out any fine tuning effects, if any need remains...

A5INKY said:

... it makes zero sense to me to skip resetting lash with a cam change. ...

Click to expand...

As I've thought about this now, I keep wondering what I was thinking. Well, I "know" what I was thinking... I was just following a couple of different guides, both of which sternly warned "do not get the position of the rocker assemblies mixed up, or you will have to adjust rocker lash!" ... so, this led me (scared me?) to believe I would not have to adjust lash if I did not mix them up. But even this makes no sense to me now for a new cam install, I mean, sure, the rocker design for the injectors wears far less than the lobe-to-lifter system used for the valves, but a whole new cam introduces far too much possibility of needing a re-adjustment. Well, at least I did discover Frank06's advice on how the dial caliper method isn't necessary so it seems easy enough. Not as easy as having done it with the cam, but still.

And yeah, wholeheartedly agree also that doing the basics comes before the fine-tuning... it's just that I, being the rookie that I am, didn't have this in my "basics" list.

Thanks!

I'll adjust the lash and see what it does for the IQ.

Frank's method is easy and it works fine. Just set them in the firing order 1-3-4-2 and be sure to use the crank to turn the engine over and not the cam. If you do it during the right time in the cam swap you can reach down from the top to turn the engine over. If you wait too long and the engine mounts are back in already, I find it easier to turn the engine over by reaching up from below which means having a helper either work the wrench or watch for the rocker pin lining up with the intake lobe.

I might have to get a bigger helper though (mine is only 8 ) but if my garage floor is long enough to be able to just put it in 4th gear and push the whole car, I might be able to pull it off that way.

So, do you think I should adjust all four? Including the two that are showing spot-on IQ as well?

I'm thinking out loud about the factory-spec, and why some folks have gotten worse IQ figures after lash adjustment ... since I take it that it was devised from a "brand-new everything" perspective (cam, rocker, and injector)...
so again, I'm real curious to see how far from bottom my "good" ones are at, if they're at 180 degrees, then sweet... factory-spec it is, but if I find the good ones to be at let's say 135 degrees from bottom, and the other two in far opposite directions, in line with my theorizing, then I think I'd opt for something a nudge closer to the two good ones (accounting this way for the wear of the injector and rocker). Although, if these things are all over the place, or off to some degree where it doesn't line up with my IQ readings at all, then factory-spec (180 from bottom) it is.

Orrr, just don't mess with the good ones at all and set the others to spec.

I would start over and set all four to 180 deg out, have a beer and call it a day.

I think you are trying to draw too strong a correlation between this lash adjustment and IQ. When it comes down to it the PD unit is a mechanical pump with computer controlled spill valve system. Unlike IQ adjustments on a VE pump, the PD ECU has more control over individual injection events.

The way I look at it, The goal of lash adjustment is to create a more consistent baseline for the build up of pressure so that the ECU has a more solid base to work from when determining control signals for IQ, timing etc. I would not make any adjustments to the lash to try and "out think" the ECU. Give it a good baseline adjustment and drive on.

If you are having any injector running issues after that, then address the possibility of weak tandem pump, intermittent wiring issue, worn nozzles etc. IMO lash changes only obscure the real issue.

I'd like to add to the discussion that sometimes excessive wear on the little lash caps atop the injectors can cause some difference. I've seen some that were so worn, the little oil hole was all but mooshed over.

I always check these closely, and replace if they look badly worn.

Hi Brian, would you happen to have the part number for the lash cap?

You can easily turn the engine by putting it in 5th gear, jacking up the passenger side tire (it is handier), setting the parking brake, then turning the tire as if moving forward. Works a treat.

I do not think that setting the 'lash' will help your issue, but it certainly will not hurt.

And the ECU adjusts all injectors to balance, not just pairs.

You should always adjust the lash when replacing the cam or an injector.

I always run the adjusting screws all the way out (even when not replacing a component), then turn the engine so that the lobes for a half shaft are down (rocker tips at the injectors up) when installing the rocker shafts. This lets you run the bolts all the way down without fighting the springs on the injectors.

Adjusting screw with ball head 038130073AN about $8 (may be superseded) - screws into the rocker tip, and
Ballpin 038109527N about $18 (may be superseded) - the 'lash cap' mentioned above.

Someone please verify my part numbers - I am not very good at this.

You can often get a new ballpin with a seal kit, at least the Bosch seal kits, like this one from IDParts.com:
http://www.idparts.com/catalog/product_info.php?products_id=1482

and IDParts also sell the adjusting screw with ball head: http://www.idparts.com/catalog/product_info.php?cPath=29_115&products_id=2427.

I usually replace both together, though this may not be required.

Not all PD engines use the same pins.

BEW: 038-130-335-A, superceded to WHT-001-516
BHW, BRM, BKW: WHT-002-791

In all cases, however, they are available seperately OR included in the injector seal kit.

It was my understanding that those two numbers crossed to each other, is this not the case?

Not according to my ETKA, but it is a couple steps behind the most current. I've purchased both of those part numbers as recently as a couple months ago and they were both still available.

Wait, hang on.... the BEW one was superceded, to: WHT-001-516, they just still show the old number.