997 DFI valves coking up / injector fault .

maph · 8 Nov 2019

Likewise on lots of BMW engines it is common........I have just had a walnut clean carried out on one of my other cars a BMW 335i N54. At 80K miles they were looking pretty coked up. Before and after....

The N54 is notorious for it. I have fitted a catch can which apparently helps, not sure if that is an option on these Porsche engines.

My impressions after were that it ran slightly smoother on idle, was running really well considering how coked up they looked.

I had the turbos rebuilt and suspension refreshed at the same time so cannot comment on fuel economy....it is using the same or more but I am probably moving faster

Be interested in your results with the water cleaning as it looks like a lot of labour to get to them to use walnut blasting. I used an indy for it but know that my local BMW dealer offers walnut blasting as well so wonder whether OPCs will offer it if it becomes an issue.

Either way would be good for you to be able to offer/ become experts in it as it could be a great little niche :thumb:

Phil 997 · 8 Nov 2019

About a year or so ago I had my gen2 engine cleaned with the hydroflow system , I chose this type as I read that the ones that use chemicals can corrode the inner engine . this system is only water ,apparently it creates hydrogen that burns hotter than petrol so burns off the carbon deposits . I am not an engineer so have no idea if thats a fair explanation . my milage was around 60k and the car seems to run better more smoothly and the mpg went up by about 2mpg but I do a lot of town driving so maybe more if it was more rural driving.

https://www.topgear.co.uk/hydroflow

Disco · 8 Nov 2019

GMG said:
...could this issue become this engines Achilles heel, plaguing it just like the M96/7 frailties have ?

Not really - it was an expected issue when the car was launched as by then it was already common with DFI Volkswagens. Indeed right from the announcement there was a not uncommon perspective that people looking to keep them long term might be better buying the non-DFI 3.6 (which was only down 10hp on the gen 1 S) than the DFI S model in order to avoid the prospective issue.

GMG · 8 Nov 2019

...Thanks...I don't really understand the technology however it does seem to create as many problems as it solves !

Tourist · 8 Nov 2019

Disco said:
GMG said:

...could this issue become this engines Achilles heel, plaguing it just like the M96/7 frailties have ?

Click to expand...

Not really - it was an expected issue when the car was launched as by then it was already common with DFI Volkswagens. Indeed right from the announcement there was a not uncommon perspective that people looking to keep them long term might be better buying the non-DFI 3.6 (which was only down 10hp on the gen 1 S) than the DFI S model in order to avoid the prospective issue.

There was a picture doing the rounds showing some fuel may reach the valve area in 9A1 DFI engines. This is seemingly not the case.

My recollection is only the 987.2 Cayman 2.9 engine was non-DFI (I've got a 3.4!!!).

Beats bore scoring and IMS problems though.

Thanks OP for the insight.

MattyR · 8 Nov 2019

Wasn't the B7 RS4 renowned for this? Isn't a good old Italian tune-up the cure?.. :thumb:

deMort · 8 Nov 2019

Some more images of before and after walnut cleaning plus one of what the injector looks like when installed .

FZP · 8 Nov 2019

That is quite the improvement.

deMort · 8 Nov 2019

For now this is something we are working on at work .. walnut cleaning is not really feasible with the engine in situ .. we just don't have good enough access hence we will be trialing the cleaning machines in a few weeks time .

We also cant clean the cylinder heads / pistons this way ..

walnuts are used as they are soft .. if a single particle ends up in the cylinder then it wont do any damage ... also a bit messy as it tends to go everywhere !

Can't spin the engine over to use compression i'm afraid to remove it .. high pressure fuel system which is removed to get to the injector .. bit dangerous

.. Also running the pump dry is not good for it .

This is not an achilles heel so no one wants to worry unduly about this .. a slight lack of power or a higher usage of fuel is what i expect would be the only issue with this problem at this sort of mileage .

Injector spray onto the valve when open is indeed supposed to help .. it doesn't seem to though .

For my way of thinking this is due to the closed crankcase system .. engine gasses and indeed oil being in the intake will cause this ... hence fuel type , how its driven won't really make any difference .. what's in the inlet tract will though .

Normally fuel will help clean the valves but as in this case and on other makes of cars then it seems it's a common fault of this type of design .

red X .. ahh yes .. in theory it would work here as well .. down side is the engines are highly tuned these days so they might not appreciate running on that stuff .. brings back memories though .. 5 pound of 4 star and a shot of red X please !!!

Phil 997 is the only person i know to have actually had it cleaned out .. i remember you first posting about it .. that's pretty much when we first started to look into this fault ..

You are our inspiration young man

For now .. we test things .. and that usually means to the death to come up with a solution .. probably like all garages .. we need to prove something works effectively before we offer it as a service ... in short .. you lot are getting an early look at a work in progress

Anyways .. don't forget i posted above this first with more images ..

MattyR · 8 Nov 2019

deMort said:
For now this is something we are working on at work .. walnut cleaning is not really feasible with the engine in situ .. we just don't have good enough access hence we will be trialing the cleaning machines in a few weeks time .

We also cant clean the cylinder heads / pistons this way ..

walnuts are used as they are soft .. if a single particle ends up in the cylinder then it wont do any damage ... also a bit messy as it tends to go everywhere !

Can't spin the engine over to use compression i'm afraid to remove it .. high pressure fuel system which is removed to get to the injector .. bit dangerous .. Also running the pump dry is not good for it .

This is not an achilles heel so no one wants to worry unduly about this .. a slight lack of power or a higher usage of fuel is what i expect would be the only issue with this problem at this sort of mileage .

Injector spray onto the valve when open is indeed supposed to help .. it doesn't seem to though .

For my way of thinking this is due to the closed crankcase system .. engine gasses and indeed oil being in the intake will cause this ... hence fuel type , how its driven won't really make any difference .. what's in the inlet tract will though .

Normally fuel will help clean the valves but as in this case and on other makes of cars then it seems it's a common fault of this type of design .

red X .. ahh yes .. in theory it would work here as well .. down side is the engines are highly tuned these days so they might not appreciate running on that stuff .. brings back memories though .. 5 pound of 4 star and a shot of red X please !!!

Phil 997 is the only person i know to have actually had it cleaned out .. i remember you first posting about it .. that's pretty much when we first started to look into this fault ..

You are our inspiration young man

For now .. we test things .. and that usually means to the death to come up with a solution .. probably like all garages .. we need to prove something works effectively before we offer it as a service ... in short .. you lot are getting an early look at a work in progress

Anyways .. don't forget i posted above this first with more images ..

Thanks for the insight Iain. Good to know that you chaps are doing this R&D. It'll keep our cars on the road a bit longer and in fine fettle :thumbs:

Luddite · 9 Nov 2019

Thanks so much for providing the insight to this aspect of modern engine design Iain..one I had not contemplated till I read your post. Also thanks for the up dated series of pics..

It seems as if the internal combustion engine is going full circle, back to a time when engines had to be DE-COKED on a regular basis... though if circa 70k miles in the interim period then that beats the vintage era..(-:

Closed crankcase breathing as has been the norm for years equating to engines having to ingest their own crankcase generated fumes, seems to have been exacerbated by direct injection to the cylinder as opposed to the inlet valves being washed by the fuel as it was with indirect injection or carburation.. DI thus causing build up of crud in the inlet tract and exposed valve surfaces, perhaps being baked on given the temperatures involved...hmm..?

Seems like a new generation and more refined AOS design may be preferable as opposed to inventing a simpler cleaning process..?

I have not a clue if the old idea of an Italian tune up might still work as it once did, though seldom used engines that may spend a fair percentage of their life sitting in slow moving traffic may be even more susceptible to this crud than those that may be fortunate enough to see more regular use...?

Yup I suspect the old chemical additive methods where the crud ended up being blown out the exhaust system would kill a cat, thus if cleaning is required or desired it would seem best to extract the crud directly from the exhaust tract.... But for me the benefits would have to be VERY real before getting involved in that process, and all the possibilities of risk and cost relative to gaining access.

Sorry if my lack of ability to express myself in print caused you to think I suggested using fuel pressure to extract a stuck injector, instead of CAREFULLY using cylinder compression to assist the process... thus no fuel pump or starter motor involvement, more turning the engine by other means to create pressure in the offending cylinder.. Though I did point out that there were RISKS involved, which in these times of elf`n safety are BEST avoided by those who do not understand the risks involved..The flying injector I mentioned weighed in at circa 1/2 a pound and stopped when it hit a concrete roof of a bomb proof bunker, creating a mushroom effect on the threads of the fuel connection point...So yes, without understanding of the forces involved, it is possible if not probable to do a bit of damage... or worse..

Tourist, thanks for posting the cutaway diagram, though given it seems it can be difficult to remove spark plugs, I wonder if in reality any of the threads project beyond the head into the combustion chamber on some engines... though I would hope not..!

Just thinking in type... :?:

alpinaman · 9 Nov 2019

Back in the 90's i was a tech at a Mitsubishi main dealer,i believe they were the first in the UK to introduce high pressure petrol engines into production cars.(GDI)
We had issues with them coking up the valve stems after 60k miles approx.

Walnut blasting was in its infancy and worked well.

But so did a gradual introduction of brake fluid into the inlet manifold whilst the engine was running..

Worked a treat

Luddite · 9 Nov 2019

:floor: :floor: :floor:

deMort · 9 Nov 2019

Luddite said:
Closed crankcase breathing as has been the norm for years equating to engines having to ingest their own crankcase generated fumes, seems to have been exacerbated by direct injection to the cylinder as opposed to the inlet valves being washed by the fuel as it was with indirect injection or carburation.. DI thus causing build up of crud in the inlet tract and exposed valve surfaces, perhaps being baked on given the temperatures involved...hmm..?

Yup .. that's what's happening basically .

Luddite said:
Seems like a new generation and more refined AOS design may be preferable as opposed to inventing a simpler cleaning process..?

It's hard to separate air from oil without an oil mist being included .. hence the AOS does what it can .. a better system might be made but cost , weight and even if it's feasible are questions that needs to be considered .

Luddite said:
I have not a clue if the old idea of an Italian tune up might still work as it once did, though seldom used engines that may spend a fair percentage of their life sitting in slow moving traffic may be even more susceptible to this crud than those that may be fortunate enough to see more regular use...?

There is no fuel injection into the inlet manifold so nothing to clean the valves .. running it high RPM will make no difference as nothing changes other than the amount of air flowing through the inlet manifold .

Luddite said:
Yup I suspect the old chemical additive methods where the crud ended up being blown out the exhaust system would kill a cat, thus if cleaning is required or desired it would seem best to extract the crud directly from the exhaust tract.... But for me the benefits would have to be VERY real before getting involved in that process, and all the possibilities of risk and cost relative to gaining access.

The new machines break down the carbon build up so no large chunks go anywhere .. it burns the deposits off as i understand it .. but we have yet to have the company come in to demoe them and explain the operation so atm .. that's my assumption .. it had better be correct or this system could well damage items !!

Luddite said:
Sorry if my lack of ability to express myself in print caused you to think I suggested using fuel pressure to extract a stuck injector, instead of CAREFULLY using cylinder compression to assist the process... thus no fuel pump or starter motor involvement, more turning the engine by other means to create pressure in the offending cylinder.. Though I did point out that there were RISKS involved, which in these times of elf`n safety are BEST avoided by those who do not understand the risks involved..The flying injector I mentioned weighed in at circa 1/2 a pound and stopped when it hit a concrete roof of a bomb proof bunker, creating a mushroom effect on the threads of the fuel connection point...So yes, without understanding of the forces involved, it is possible if not probable to do a bit of damage... or worse..

:

It was considered to use compression to get the injector out at the beginning .. these engines though are a little hard to turn over .. there is little access to the crank pulley with the engine in situ and at best we would get a slow turn of the engine to increase compression on that cyl ...

Basically it was never going to work .. it was jammed in there to the point we made up a slide hammer and fixing tool to remove it once the engine was out... it didn't work in situ.

Spark plugs do indeed enter the cyl by a couple of threads .. it's this part that carbons up and makes the plugs on these problematic to remove .

I don't often do a full response to your posts as it takes quite a while to answer every part of what you mention .. always interesting to read though .

So i thought i would on this one

Phil 997 · 9 Nov 2019

deMort said:
Phil 997 is the only person i know to have actually had it cleaned out .. i remember you first posting about it .. that's pretty much when we first started to look into this fault ..

You are our inspiration young man

For now .. we test things .. and that usually means to the death to come up with a solution .. probably like all garages .. we need to prove something works effectively before we offer it as a service ... in short .. you lot are getting an early look at a work in progress

Thank you Ian , I am watching how you and the team progress closely as I know whatever you end up offering will be a perfect solution to what is going to be potentially something the gen2 will need doing as they start to get to 60/70k miles . :thumb:
It great for us owners to know that there are Porsche specialists out their being proactive in finding solutions to potentially inherent issues before they become a real problem :thumb: :thumb:

997 DFI valves coking up / injector fault .

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