ALH Injector Replacement Interval

Before I get flamed, I did a search with inconclusive results to my question.

I have an '03 Jetta with 165K mikes now on the original injectors. I have noticed that over time the engine seems to have more of a diesel knock to it.

I know the injection timing is good and the cam timing is good. I had the IP gone through by DFIS. I do all of my own maintenance (have VAGCOM) and keep the car in good running order.

I know if the pop pressure drops below 200 bar Robert Bosch's minions say the injector is worn out of spec.

I have not in all of my searching seen an answer to the question of does replacing old injectors restore any power or make the engine run smother. I would like to replace with the same size injectors because of the dreaded autotragic (wifey demands 2 pedals).

I plan on the instant gratification replacement in the near future. Just wondering what to expect from my investment.

Anyone have anything to report on replacing high mileage (150k +) injectors?

I suspect you'll get various answers. Some will tell you they have 300,000 miles on the original injectors while others will say to replace them every 100,000. Like anything else, lots of variables determine the longevity of a given part.

Replacing yours with a stock sized injector probably won't make a huge difference if the engine already runs well- you could probably run a can or two of diesel purge through the ones you have and you'd be fine.

Just by virtue of reading this however, you evidently take an interest in the car and if you are like me, you want to keep it running at its best. I have 197,000 miles on original injectors and plan to go with a stage I tune first, then see about injectors. My reading has told me that the PowerPlus 357 injectors are a good stock sized upgrade for a manual trans car, and would work well in your auto trans car.

Since ALH has the same injectors as my 1Z I can tell you mine is about to tick over 413k on original pump (just resealed) injectors and nozzles. I am gonna finally put in my PP520s n RC3 chip in soon... I will share my injector test results

bjleger- My own thoughts are similar to yours. I tend to advocate taking an active approach to maintenance and keeping the car in top running condition. I have same situation with my 02 Jetta... It has 290K+ miles on the original IP and injectors. It still starts and runs very well. I recently did a (3rd) timing belt job, and I thought very hard about replacing the IP while everything was apart, just because of the mileage. Ultimately I chose not to, because the engine runs well and still gets 50MPG and no bad noises etc. I did buy a new set of injector nozzles (not installed yet) mainly because I found them on sale at idparts. I figure the nozzles must be crudded up after 290K miles, but I'm also reluctant to mess with anything because it runs well. MPG has decreased about 2-3 from new, it would get 52-53MPG. Part of me thinks maybe the new nozzles might help that. Other part of me thinks- if it ain't broke, don't fix it.

Noting your car is an auto trans and your sig, no doubt you have seen the rants about autos. Wonder if you might want to bankroll your next auto trans or conversion to 5speed etc. Good luck with your decision.

Does anyone have any data on the pop oressures of worn-used injectors. I know, why would you pop test old injectors. Just would like to satisfy my curiosity. maybe Frank06 would be the one to answwer this.