1997 Jetta TDI Liqui Moly Question

So, it's time for me to clean the fuel injectors in my wife's MK3 Jetta and was wondering if anyone has had any issues running Liqui Moly diesel purge straight through the injection pump (i.e.. not added to the fuel tank as an additive)?

I have done it before on my '82 Benz 300 TD with no issues. But I have also done this on my wife's Jetta before and shortly thereafter the pump started leaking . So I'm wondering if that was just a fluke or if the concentrated Liquid Moly damaged the seals in the pump.

Has anyone else had a similar issue? I just don't want to damage another injection pump.

100% fluke, if the seal started leaking due to the fuel cleaner it was toast to start with and this just made it show up. 100% safe. put the intake and the return into a large can and fill with liquid molly and run until you consume most of it, will take a few minutes, took me 12 minutes to take about 2 cups of it. How many miles on the injectors? stock? anything past 200K and you would be better off just doing a small upgrade on nozzles from kerma with a pop test, next size up or two would be fine on a stock engine with no tune needed.

Thanks Mongler98! I think I'll go ahead and give the ole' Liqui Moly another try. If that doesn't do the trick then I'll probably have to replace the injector nozzles. The do have almost 300,000 miles on them after all!

what is wrong with them. Why you think you need to? Do you still have the EGR system on the car? or have you cleaned the head and done a EGR delete?

The EGR was removed about 5 years ago. So now that leaves me to think that the recent loss of power when climbing hills is due to dirty fuel injectors.

Here is a check list for you in priority of most likly to most expensive/labor heavy task

MAF check, run with it unplugged and plugged in, if its the same you have a dirty or dead maf. Clean with MAF spray $8 or replace with OEM $$$$$

check all your vacuum lines (boost lines) Replace if necessary $10. Check the n75 valve. clean it if necessary with maf cleaner (NOT BREAK CLEAN) Replace if its dead $75

make sure no boost leaks (there should be oil in the boost lines) check for wet oil areas at intercooler and pipes etc.. Replace if necessary or fix

Check air filter

Fuel filter replacement if it has been more than 50K miles. I suggest the Ditzel mod or nictane fuel filter. Check all your fuel lines. its a draw system so it wont squirt out but will be wet.

At lastly i know 100% your head is less than optimal. You want to pull the head off and get a new head gasket. the swirl ports on the intake are 100% compacted with oil soot.



Your intake manifold is just as bad too.

This would not solve your current issue of loss of power but its something to put on your list.

fuel injectors dont get very dirty as you think but its not going to hurt it. that would be step one. step 2 is to check up on everything before you check out injection. Check your IP's IQ with VCDS, you can hammer mod it. You might want to look up keystone mod. There is a plunger on the IP and the key way can fall down a bit. All you do is take it off, clean it up, take it to a weld shop or yourself can do this and put a tack weld on the spring retainer and the body with a TIG to keep it from falling again. this is for top end power sort of thing and might be one of the culprits.

Wow, thanks for the list. I will start working my way through it one by one. This is very helpful!

Mongler98 said:

At lastly i know 100% your head is less than optimal. You want to pull the head off and get a new head gasket. the swirl ports on the intake are 100% compacted with oil soot.

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Was that run on WVO or Veg? I have never, ever, seen a head that dirty from diesel. Ever.

Here are a few pictures of mine when I had to replace a head gasket at 383,400 miles due to a failed water pump, the engine was previously uncracked. You can still read the writing on top of the pistons and see the cross hatching.



I installed a junkyard but Franko6 refreshed head and tossed the old one in a box, which I still have and can get pictures of if needed, but it looks just as clean.




I've torn the heads off more than a few of these and transplanted them for people with head issues and never seen even 1/4 as bad as that. Most are quite clean inside.

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As to the Keystone mod, some people on here were selling the Keystone Keys a few years ago but stopped. I took measurements and here they are to make your own key.



And it goes here:



Normally you can remove it with just a 10mm wrench, but I made my own socket because I've run across some stuck ones. If you decide to do this, do not use a thick walled socket since there isn't a lot of room there and this one only fits on one way.




When you remove the valve, it'll probably be popped out like this. Just press the end flush with some pliers or a vise.




And don't worry, it will deform some when installed, so you will feel a little tension screwing the valve back in.

I grabbed the picture of the head off google because i dont have any from when i did mine to be equal in representation. When i did the ERG delete 5 years ago i took the valve cover off and made it so that no valve was being pressed on the intake side. then i took a variety of plastic picks and screwdrivers and such and scrapped the crap out of the head as best i could with my head wedged between the head and the fire wall to see what i was doing. i took a sucker for bleeding brakes with a air supply and sucked out what i would spray in with brake cleaner fluid. took about 1 hour and 2 cans each port but i cleaned them really well and when i took the head off i was surprised how much i had gotten. i would not get the other side of the valve and the 3 years of driving around with no EGR and just oil mist blasting away cleaned most of it up. MY intake was a different story and was about this clogged up when i deleted and installed pd150