Should the IQ numbers be close?

Started having some power issues today then later got a P0251 code. Hooked up VAG Com and read;
IQ Cyl 1: .40 mg/str
IQ Cyl 2: .75 mg/str
IQ Cyl 3: -1.79 mg/str
IQ Cyl 4: .61 mg/str

Injection system has 310k, I rebuilt entire engine 90k ago but I have no experience with the fuel system. Is my problem in the injector or in the pump, or is there not enough info to know for sure. Any advice is appreciated.

Tonight, I just buttoned up a TB Job on my ol' 2000 Jetta, 369k miles. While fine tuning the timing using VCDS, I observed the various engine functions. The IQ varied similar to yours.

I have no desire to mess with anything as those numbers are all within spec. The engine runs just fine. In fact, for the miles and being practically all OE, it is probably the cleanest engine (top to bottom) as in, virtually zero oil leaks, starts great, runs great, and still knocking out 50+ MPGs from tank to tank!

Sure, you can pull the injectors and have them balanced and those numbers will be a bit closer if not almost the same! Is it worth it, maybe and maybe not, in my opinion.

Most people would have had the injectors checked or rebuilt over 100k miles ago. I would get some .205 nozzles, get them professionally assembled and tested and call it good. If at some point you would like to get a bit more power out of your engine the .205 nozzles will work fine up to Stage3.

Altho Andybees is probably a lot closer to being a guru , rather than I am , I have played extensively with injectors and IQ numbers and my recollection of "within spec" differs to his. I thought that anything in excess of +/- 0.50 is cause for concern... I know the Ross tech software wont acknowledge anything in excess of 1.88. I believe the OP needs to at least acquire a set of good used original injectors if he doesnt want to go the expense of 205s and the associated setting up costs.

I managed to get my values within 0.18 just by experimenting with used units

When I hover the cursor over the values in VCDS, it shows all of mine to be within spec. My worse deviation from the average of the others is not as far off as the OPs posted numbers. But, as I recall, his numbers seem to be within spec per VCDS.

Considering I have drivcen my 2000 Jetta conservatively from practically all aspects and it is at 369k miles, starts good, runs good, and gives outstanding MPGs from tank to tank (and that it will soon to be titled over to my son), I have no reason to be pulling and playing with injector swaps (and I have a good number to chose from).

Here is one pic of the underside taken about two weeks ago. OE crush washer on the oil drain plug.... Notice, clean as a whistle.... it had zero oil leaks except for a slightly wet cam seal on the sprocket end. I guess in summary, not broken, don't fix. (I've seen many with way less miles that were an oily mess on the bottom and top as well that needed far more than basic maintenance)

Ok, if we are going to talk what 'specs' are good, let's see... where should be start?

33 ft lbs on the cam sprocket for an ALH. When the AHU was 54 ft lbs and the PD was 74? That number got me a whole lotta cylinder head rebuilds...Almost as many as Prothe.
.051" rock measurement for valve guides. My pilot guide bangs to the bottom and rattles.
And now, it's -1.79 is ok with injectors? We base our quality on the lack of disparity in that number.

We recently got measurements from two different sets of injectors (and it's not a max of 1.88 deviation... PD's can deviate -2.99 to 3.01) But anyway, with the nozzles way out of range, the two owners melted out two each pistons. That amounted to roughly $8000 worth of engine builds. You would think competition would want to make quality instead of quantity.


You can all do whatever you want, but if you destroy your engine by melting the pistons out, remember what I just said.

Now, Frank, you're not going to cause me to start wringing my hands! ...

I do wish I'd done a screen shot of the IQ numbers down through the years.

Which one of those Injectors in the OP's post do you think has the greatest likelihood of burning a piston?

Sorry, didn't mean to ignite such a fiery discussion! I just wanted to see if I should replace my injectors or my injection pump- I can't afford to do both right now. I will say that when the P0251 code eventually pops up and it runs like chit, I clear it and it runs fine again for a few days. I've done ZERO to the fuel system other than replace the filter every 20k. Everything is stock except for a Malone Ecotune.

Which one of those Injectors in the OP's post do you think has the greatest likelihood of burning a piston?[/QUOTE]

Yes this would be helpful.

What's P0251 for?

I've read that those variations can be caused by other things than the injectors. You could try swapping them around and see if the numbers stay with the injectors or the holes.

DTC P0251

https://www.yourmechanic.com/articl...lfunction-cam-rotor-injector-by-blake-griffin

Thanks Andy I could have looked it up but Idunno. Seems if a guy's looking for help he should make it as easy as possible for the helpers.

KLXD said:

Thanks Andy I could have looked it up but Idunno. Seems if a guy's looking for help he should make it as easy as possible for the helpers.

Click to expand...

A DTC will only get you close. I gathered some info I thought was relevant to this issue from the VAG COM and was asking if there is a connection.

Nitrocharger, I think we've all learned a bit from this Thread.

As I stated, the IQ numbers on my engine were very similar (but without a DTC).

KLXD, the info on that DTC was very informative. If you had posted the link, it's possible that I might not have clicked and looked/read.

I respect Frank's contribution, which, by the way, those of who know him, understand it is based on daily hands-on work, research, etc.

As we all know, sometimes multiple issues causing the same DTC are difficult to iron-out and can result in throwing parts unnecessarily. Presently, I've been working on a BEW engine that's a hard starter. It had two DTCs. One for crankshaft position sensor and the other related to the engine Temp Sensor. Before re-setting the Torsion Value, I wanted the engine/ECU to repeat those codes after I deleted them.. but, seems it will not! Thus, the question, do I re-set the T Value and see what happens with starting or do I replace parts as well?