Porsche 911UK Forum

Welcome to the @Porsche911UK website. Register a free account today to become a member! Sign up is quick and easy, then you can view, participate in topics and posts across the site that covers all things Porsche.

Already registered and looking to recovery your account, select 'login in' and then the 'forget your password' option.

997 DFI valves coking up / injector fault .

deMort

Well-known member
Joined
21 Mar 2015
Messages
11,244
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 .
 

Attachments

  • engine_399.jpg
    engine_399.jpg
    486.9 KB · Views: 5,241
  • aos_140.jpg
    aos_140.jpg
    409.3 KB · Views: 5,241
  • valves_523.jpg
    valves_523.jpg
    379 KB · Views: 5,241
  • valves_1_769.jpg
    valves_1_769.jpg
    414.1 KB · Views: 5,240
Now I finally have a visual of why My plugs weren't keen on bring replaced. :eek:
 
Thanks for the info Ian. What mileage had this car covered. Is it to be expected on higher mileage cars?
 
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.
 
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...? :?:
 
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.
 
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 :)
 
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.. :eek:ld:
 
...could this issue become this engines Achilles heel, plaguing it just like the M96/7 frailties have ?

...could we see stuck and broken valves ?
 
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 :? ) process .
I guess its another reason to pay close scrutiny to past services being done correctly & on time when purchasing
 
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. :lol:
 
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.
 
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.
 

New Threads

Forum statistics

Threads
124,353
Messages
1,439,439
Members
48,708
Latest member
JLav211
Back
Top