2.9 987.2, old problem or a new one?

[911hillclimber]

I've owned my 2.9 / 2009 Boxster since March 2016 and the ups and downs of the car come and go. Recently the car has been great, just needing washes and driving!
However...
I have noticed a return to some extent the return of smoke on cold start since getting back from a Euro trip a few months ago.
I do NOT think this is an AOS issue, the smoke is NOT that bad, so lets put that to one side.
That smoke issue was fixed by dropping the oil level when hot one segment below FULL, worked a charm, and that was about 3 years ago.(thank you Laura).

The car is now just on 80K miles, the car is rarely run hard, just holiday cruises and nice days out, 34 mpg is quite normal, and it has run on E10 for years though I used E5 on the recent Eurotour.
The car was serviced as ever by the excellent Zuffenhaus in Birmingham just before the trip.
Car uses no oil, has no rattles, and runs clean on the road.
All in all, a nice honest little basic Boxster which I fall in and out of love with regularly esp when it gives me grief.

Since back from Europe the car has belched a fuel/rich smoke on start up roughly every 4th or 5th cold start. If the car is moved repeatedly on the drive it can or does not do it. A week after a day run it might or might not do it. In all these episodes the car is parked on my level drive.

I might estimate the smoke volume is about 5% of 'AOS smoke', just trying to put all this into perspective.

What controls the enrichment for cold start fuelling?

I presume the ECU checks the temperature when ignition is switched on, passes a level of fuel to the injection and cranks the engine, thus all factory set.
Is there anything else that comes into play that influences the level of fuelling?

OR
Does anyone have any advice/ideas?

Off to Scotland soon to clear it's throat, but would like to get some thoughts please.
Thanks, Graham.

 

[Motorhead]

Graham,

I suppose the sensible thing to do is to run some decent Porsche-specific diagnostics to see if anything’s flagged-up, but at that sort of mileage maybe the MAF sensor could do with a clean or replacement? It’s a bit odd that the problem’s intermittent though.

Jeff

Edit: Cold start valve sticking perhaps? If you can find it, try giving it a tap.

 

[911hillclimber]

Thanks Jeff, thinking of taking it to Zuffenhaus for a run through there box of tricks before Scotland.

Off to find that valve.

 

[andywill]

HI Graham

Just my 2p.

Could be something as simple as oil seeping past into cylinders. What grade oil are you using? At 80K a thicker grade may help at next service. Oil cap should be easy to remove when running. if not think. AOS.

Good luck

 

[911hillclimber]

Thanks for the thoughts Andy. Been through the AOS story some years ago and even fitted 2 of them. I'm sure the AOS is sound, but will check again.

The smoke is not as intense.volumous as the AOS commonly is, or over fill of oil where oil enters the cylinder(s) down the inlet past or on the inlet valve head.

Dropping the oil level to one segment empty essentially cured that one years ago, but this morning the engine started really crisply but still belched out smoke.

The same smoke as when a month ago I restarted the engine cold after 3 previous short starts on the drive moving the car around.

Most times all is well, clean start, no smoke.

There is no rhyme or reason to it, totally random.

 

[911hillclimber]

Had a couple of small white smoke belches recently, so looking to fit a new cold start injector. Can't seem to find where this is located on the engine (2.9 remember) and if it is a DIY access job.

Any ideas or pointers please?

Must be on the inlet plenum??

 

[Motorhead]

I’m not sure that there’s a cold start injector Graham, although there’s probably a cold start valve somewhere in the system.

If you want to sift through the PET for your 2.9L 987.2 you may be able to find it:

https://www.porsche.com/uk/accessoriesandservice/classic/genuineparts/originalpartscatalogue/

Jeff

 

[911hillclimber]

Thank you Jeff.

It is hard to locate if there is one (I would expect the engine management to deal with the enrichment of the cold start via the fueling map), and if

there is one where it may be. I will have a browse.

 

[AndrewCS]

White smoke ? ... condensation / coolant / excess fuel

Leaky injector ?

How was the last MoT emissions test - reading ?

Time for a few low gear - high rev. runs .... up a hill-climb perhaps []

 

[911hillclimber]

I think white smoke is oil being burnt in the cylinder.

Engine starts just as normal and a second or 2 out it comes.

not sure if it is from both sides of the engine or one side.

Certainly is irritating, and makes cold start a bit nervy!

Engine clears very quickly, 1 or 2 secs, but the small plume of smoke lingers...

An Italian Service?

could be so.

Fact I get 34 mpg, some trips 36 or more means I'm treating it toooo easy.

It flies through the MoT but gets tested hot, not from cold.

Coolent level never changes, oil level right, never needs topping up between services.

 

[AndrewT]

I’m not sure that the Italian service will solve the problem for you. When you solved this problem previously as well as changing the AOS didn’t you clean the associated tubes & hoses? Could it be that operation of the AOS is borderline on even the lowest mileage engines and is just not up to the job of operating correctly on a 70/80k mile engine, perhaps on the older engine it needs to be treated as a service item?

As I’m sure you’ll recall I used to have the same problem on my 2.9 Cayman, the original owner reported that it started happening at about 60k miles. It was the unpredictability of it that I found frustrating, it even occurred once on restarting in the paddock at Gurston after I’d already done one run up the hill which was pretty much the equivalent of an Italian tune up I’d say. A new AOS improved matters but did not cure it, I don’t know whether the associated tubes/hoses were clean when it was changed.

Good luck, I hope you can make the problem go away again for a while.

 

[911hillclimber]

Yes, when I did the last AOS I had the tubes free of the unit for change over and flushed the tubes out. There was oil in the tubes (than allow oil to dribble down to the inlet) but the old AOS was sound, ie the diaphragm was intact.

However, it is a good reminder for me and just cleaning those tubes is no big deal.

Thank you for that, will give it a go soon and report back on what/how much is inside the tubes.

 

[911hillclimber]

Decided to take a look at the tubes leading from the AOS to the inlet, and clean if oil present.

When I replaced the AOS it was in August 2019, so 4 years old. (I mark up all major parts i change for those who get the cars later!).

Pipe is one assembly, 3 connections, all squeeze and pull types and very accessible. Off, there was oil present at every connection, stuck my finger into the AOS outlet ( where the tube fits) and there was lots of oil, almost as if there was a pool there.

Similarly, there was oil present where the tube splits to enter the inlet chamber, not lots, but oil.

I feel this is where the oil is seeping into on the odd occasions to one of the cylinder's inlet valves and to the chamber if that valve is open.

Cleaned the tube lengths vigorously with big blasts of brake cleaner and long blasts of compressed air to dry it off.

All back together now.

At least the tube is clean, the bulk of the oil pool in the AOS is wiped out.

So, this engine should be smoke free for a while. Took all of 45 mins the lot, tube cleaning 10 mins.

Trying to find the enthusiasm to replace the AOS, the car's third...

It is a pig of a job, almost not enough room but obviously doable, FAR easier than a 986!

Time will tell. There will be a drop or so oil trapped still in the inlet, so might get a few more smokey cold starts yet.

 

[Motorhead]

It sounds as though your AOS is more like a service item Graham … replace every every 2-years/20,000 miles!

You have to question the integrity of its design/manufacture, or maybe you’ve just been very unlucky.

Hope cleaning the pipes turns out to be more than just a temporary fix.

Jeff

 

[AndrewCS]

Perhaps this ... Oil Separator Boot for Porsche 996 3.4L 1998-02 / Boxster 986 - AOSKIT987 | Design 911 would help ?

Have you suffered from packed up oil separator? Are you worried that it will ruin your track day experience? This twin chamber conversion kit will put your mind at ease. Porsche has developed Motorsport version of AOS to avoid future problems. Fit and forget. Porsche Fits: Porsche 987 Boxster Porsche 987C Cayman

 

[AndrewT]

I have my fingers crossed Graham that your cleaned tubes will leave the car smoke free for several thousand more miles! It’s so frustrating when you can’t recreate the problem at will.

Having sold my 2.9 Cayman, which had that smoking habit, and moved on to a much lower mileage 987.2 I was dismayed to get the same cloud of smoke a couple of times during my UK tour in 2019. The engine had been serviced shortly before I left home, the oil level was at maximum, yet the smoking episode happened several days and a few hundred miles later but then never again during my ownership of the car. Mysterious indeed.

 

[AndrewT]

Perhaps this ... Oil Separator Boot for Porsche 996 3.4L 1998-02 / Boxster 986 - AOSKIT987 | Design 911 would help ?

Have you suffered from packed up oil separator? Are you worried that it will ruin your track day experience? This twin chamber conversion kit will put your mind at ease. Porsche has developed Motorsport version of AOS to avoid future problems. Fit and forget. Porsche Fits: Porsche 987 Boxster Porsche 987C Cayman

The question is how much smoke & embarrassment would you tolerate to avoid spending £1,536.14?

 

[911hillclimber]

Have seen those recently!

£1500 to solve a problem if you use a sports car for sport.

Normal genuine AOS for the car is around £90 on my doorstep, 1500 /90 = 16 AOS changes!

Just another poor engineered part on these and other types of Porsche, I expected much better with the 987.2 after the experience of the 986's.

iirc Zuffenhaus want an hour to replace the AOS (they are welcome to the job) so £200 a 'service' as Jeff suggests, irritating, but not crippling.

When i replaced mine the second time myself I dissected the AOS and could see nothing wrong with it, all parts ok, so what is happening?

A design that does not work??

I hope my clean-out has worked for a while, 45 mins and no cost and you get to clear the drains out at the same time!