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deMort
Dijon


Joined: 21 Mar 2015
Posts: 7573
Location: Brighton


PostPosted: Wed Nov 06, 2019 8:22 pm    Post subject: 997 DFI valves coking up / injector fault . Reply with quote

I had a 997 gen 2 so the DFI engine in for a misfire fault .. another garage had looked at it but kinda moved it on .

Fault was an injector .. no actual way of testing it though .. 3 hours of stripping parts out to get at it only to find it jammed in place and i couldn't get it out.

Also no way of testing it when half the engine is in bits .. wiring tests proved that side was ok ...Fuel pressure is 48 bar on idle with upto 230 bar at times... a little dangerous to mess about with .

Engine drop .. i had a look at the valves at this point .. lets just say i took about 20 pictures but the images below are the best i could get .

Valves are heavily covered in carbon .. to be expected when there is no fuel to " clean them " .. even so it was a bit of a surprise to see just how bad they were .

We bought a walnut cleaning machine and proceed to " shot blast them" .. end result after modifying adaptors to get the best results was pretty good ..

henry the hoover got a good workout .

Still working on a way of doing this in situ but atm we feel the " water machines " for want of a better description might be best .. not sure how well they would deal with the level of carbon this car had on it though , personally i don't think they will do a thorough clean .. maybe several attempts and then see .

A lot of work and not what the customer paid but we used him as a guinea pig to work out the best way forward as this is going to be more common we feel .

For us it's a work in progress but i thought i would share it ... we learn when we get a problem .. we find a solution as does any garage that is most cost effective .


Pictures were taken after i had removed the manifold .. the dirt you see is what you all will have ... all cleaned up afterwards though .

Anyways .. i just thought you might want to have a look .

EDIT .. right click on the images and open in a new tab ... or enlarge them to get a better image .
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FZP
Estoril


Joined: 18 Jan 2015
Posts: 3851
Location: Cheshire


PostPosted: Wed Nov 06, 2019 9:00 pm    Post subject: Reply with quote

Now I finally have a visual of why My plugs weren't keen on bring replaced. Surprised
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PanozGTR
Trainee


Joined: 05 Jul 2017
Posts: 99
Location: West Sussex


PostPosted: Thu Nov 07, 2019 9:19 am    Post subject: Reply with quote

Thanks for the info Ian. What mileage had this car covered. Is it to be expected on higher mileage cars?
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Alex
Le Mans
Le Mans


Joined: 06 Mar 2014
Posts: 17120
Location: The Ribble Valley, Lancashire

2000 Porsche 996 Carrera 4

PostPosted: Thu Nov 07, 2019 9:48 am    Post subject: Reply with quote

I've made a few injector pullers for a local scrapyard. Those things are a bitch to get out without a custom made tool and then you run the risk of snapping the injector.
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MR997
Trainee


Joined: 05 Mar 2018
Posts: 55



PostPosted: Thu Nov 07, 2019 10:27 am    Post subject: Reply with quote

How log does it take to drop the engine?
 
  
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Luddite
Nürburgring


Joined: 18 Dec 2018
Posts: 494
Location: Scotland


PostPosted: Thu Nov 07, 2019 2:51 pm    Post subject: Reply with quote

Ian, thanks for relating that story, you caused the worn old starter motor in my grey matter to start cranking.... Boy did I have it easy when the release of crankcase pressure was through a steel mesh at best and then out on to the road.... then in later times when it was directed up into the air filter and a worn engine would foul the filter....to some degree adding to the exhaust emissions, but that was a while back, and interesting to note how much more complex things have become, since I owned my old SC with it`s attempts at cleaning up the emissions of the ICE engine..

Boy those watercooled Porsches seem like beasts to work on by comparrison. Seems I need to add injector removal possible list of..err.. foibles..?. Also very interesting was the need and methods you used to clean up the inlet tract, tricky stuff indeed, thanks for sharing, you are worth your weight in gold... (-:

I guess the next thing to explore may be the variety of methods tried failed and some proven to work on removing injectors...? Question
 
  
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lk993
Monza


Joined: 06 Mar 2008
Posts: 157



PostPosted: Thu Nov 07, 2019 3:29 pm    Post subject: Reply with quote

Interesting....and worrying. Yes, I'd be interesed in the mileage on that engine. Plus, because of the design and the fact that fuel isn't washing that area on a DFI, is there any way of stopping this happening? I suppose, good quality fuel won't make any differencve here.
 
  
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deMort
Dijon


Joined: 21 Mar 2015
Posts: 7573
Location: Brighton


PostPosted: Thu Nov 07, 2019 7:59 pm    Post subject: Reply with quote

Blimy this got a few more answers than i was expecting .. normally when i post stuff like this no one answers lol .

This car had done 72K miles .

To drop these engines is a similar time to 997 / 997 gen 1 .. approx 3 hrs to get it out .. can be done faster when you have done a few .. can be slower if bolts won't come out / snap etc .

the plugs are a pain as they protrude into the cylinder .. the end thread carbons up on the plug so getting them out can be a pain .. ( change them at 4 years guys .. don't go on mileage )

is it expected ? .. yes .. we were talking about just this back when they came out .. no fuel to clean the valves .. closed crankcase breather system so engine air / oil is used .. ie breather gasses are reused .. will cause this .

Fuel quality won't make any difference .. its direct injection and the crank case gasses are probably more to blame ... nothing to clean them and this is the result .

Does it cause any running issues .. now there's a question .. unfortunately i don't have an exact answer atm .. i've had running problems on cars which i thought might be down to this .. but i have yet to prove an actual problem .

i would say i kinda doubt you will get full power / fuel efficiency with valves this bad .. but thats an educated guess atm with no facts to back it up .

Air flow turbulence is what i'm thinking .

Injector was still a pain to remove even when we had the engine out .. this one was up against the oil filter housing so rubbish access to it .. we made a tool as well Alex ... in situ though and this particular injector and its still a no go with engine in .

This is all " work in progress atm " we have a demo of the " water " machines later this month .. we have a nice badly coked up Golf which we have already stripped to see the extent of the coking which we will be testing it on .. after that we will strip and inspect to see the results .

I might post them at that point if a sensible result has been achieved .

I have more pictures which i will post later of the walnut clean... need to edit them first Smile
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My Daughter's Crowdfunding has hit the target .

Thank you all so Very much .

She's not going until july 2020 though .



Mechanic

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Now At An Indy.
 
  
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Giff
Monza


Joined: 28 Apr 2013
Posts: 205



PostPosted: Thu Nov 07, 2019 9:12 pm    Post subject: Reply with quote

Time for some walnut shell

https://www.youtube.com/watch?v=ONp6gQXpyKU
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Luddite
Nürburgring


Joined: 18 Dec 2018
Posts: 494
Location: Scotland


PostPosted: Thu Nov 07, 2019 10:34 pm    Post subject: Reply with quote

Interesting stuff Ian... Given we are typing Porsche and not Lada, it seems reasonable to expect that cylinder head design might consider the length of spark plug thread in order not to create what seems to be a recurrent issue with plug threads crudding up...?

As for the valves crudding up.... when I were a lad some RED X (upper cylinder lubricant) in the fuel or more directly down the throat of the carb with the engine running.. loads of smoke.... Think in time Wurth did some sort of injector cleaner and other magic potions though I suspect cats would be at risk today..

As a yoof, I would spend time polishing ports to perfection, only to read that L J K Setright (?) reckoned a bit of rough in the induction tract caused turbulance which assisted fuel distribution in the cyl head.... Think there may have been radio active isotopes and x-ray utilised to determine flow.... All way over my head by miles..

Walnut shells... think they used that method to clean the jet fuel residue of the glass of airfield ground lighting when seeking to avoid frosting the glass.... steam cleaning was also used, if memory serves...?

Might have thought by now that AOS might have included a more efficient method of cleaning up crankcase crud rather than feeding residue back into the engine... I guess bore score may exacerbate that process, perhaps increasing the load on the AOS..?

Not got a clue as to the makeup of the injector or it`s retaining method.... but given it is injecting direct into the cylinder and not the induction manifold I wonder if compression might be used to help release it..? More thinking of compressing the cylinder by hand while tapping the sides of the injector, as opposed to using the starter motor to spit it out to who knows where.... Seen that done with a diesel where the injector became a rather dangerous projectile...

Yeah just rambling on.... don`t try ANY of this at home...Given I can be miles off target...Just passing time thinking in type.. Old
 
  
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GMG
Nürburgring


Joined: 07 Jan 2018
Posts: 459
Location: Devon


PostPosted: Fri Nov 08, 2019 6:34 am    Post subject: Reply with quote

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

...could we see stuck and broken valves ?
 
  
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me&my997
Silverstone


Joined: 23 Mar 2019
Posts: 146
Location: Lancashire


PostPosted: Fri Nov 08, 2019 10:03 am    Post subject: Reply with quote

Hhmmm , interesting if slightly disconcerting thread , it certainly sounds like a specialist job to determine the fault then rectify & by the sounds of it quite a time consuming ( costly Confused ) process .
I guess its another reason to pay close scrutiny to past services being done correctly & on time when purchasing
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Alex
Le Mans
Le Mans


Joined: 06 Mar 2014
Posts: 17120
Location: The Ribble Valley, Lancashire

2000 Porsche 996 Carrera 4

PostPosted: Fri Nov 08, 2019 10:07 am    Post subject: Reply with quote

I'd have thought this issue could happen regardless of what servicing is done. Most likely cause would either be shoite in the petrol and owners driving style.

You can't beat a good old Italian tune up. Laughing
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MaxA
Albert Park


Joined: 11 Oct 2015
Posts: 1667
Location: Helsinki


PostPosted: Fri Nov 08, 2019 10:34 am    Post subject: Reply with quote

In the MINI community, decoking the 1.6T DFI engine (as fitted to the 2nd gen R56 cars) with walnut shell is pretty common, and restores power back to factory levels.

The anecdotal evidence suggests that the harder the engine is run, the less if suffers (from the carbon deposits on the back of the valves anyway).

What a ballache though.
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Last edited by MaxA on Fri Nov 08, 2019 11:44 am; edited 1 time in total
 
  
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Alex
Le Mans
Le Mans


Joined: 06 Mar 2014
Posts: 17120
Location: The Ribble Valley, Lancashire

2000 Porsche 996 Carrera 4

PostPosted: Fri Nov 08, 2019 10:36 am    Post subject: Reply with quote

My Dad's just had to have his inlet manifold decoked on his Saab. I keep telling him its his own fault for driving like a sloth.
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maph
Monza


Joined: 01 Feb 2017
Posts: 188



PostPosted: Fri Nov 08, 2019 11:35 am    Post subject: Reply with quote

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 Smile

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
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Phil 997
Le Mans
Le Mans


Joined: 05 Dec 2015
Posts: 15551
Location: Bournemouth,Dorset

2009 Porsche 997 Carrera 4S

PostPosted: Fri Nov 08, 2019 11:44 am    Post subject: Reply with quote

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
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Disco
Estoril


Joined: 13 May 2008
Posts: 3977
Location: Hertfordshire

2010 Porsche 997 GT3

PostPosted: Fri Nov 08, 2019 1:39 pm    Post subject: Reply with quote

GMG wrote:
...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.
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GMG
Nürburgring


Joined: 07 Jan 2018
Posts: 459
Location: Devon


PostPosted: Fri Nov 08, 2019 4:13 pm    Post subject: Reply with quote

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


Joined: 20 Apr 2019
Posts: 5
Location: South-East


PostPosted: Fri Nov 08, 2019 5:04 pm    Post subject: Reply with quote

Disco wrote:
GMG wrote:
...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.


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.
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