Porsche Enthusiasts Club Forum

I imagine it does. Its the cross piece in the centre and it hisses when I hook it all up to a low pressure airline. Its is split.
Car is suddenly really lumpy, very slow to respond to the throttle especially when cold. It seems worse on the first inch or so of the throttle and less bad after that.
I didn't dare prize the AFM apart but I suppose I could.

Took me a while to to see what you was talking about, but I did think the cross junction can't be good, 2 T and some new slicone would be the route I would take.

If its a vac hose, then yeah it will matter and it will cause the symptoms you describe. So hopefully it will cure your problems

With the way your current vac circuit is plumbed up it will cause the following issues.

* Lean mixture off boost
* Rich mixture on boost
* The KLR to not see your actual boost level properly, so not retarding the ignition properly on boost
* the heater might not be working correctly

At the moment, if you are talking about the cross joiner being split, all the above will be issues of variable levels, depending on the severity of leak.

We use silicone hose with joiners as a minimum, or ideally we also use press fit metal joiners a composite plastic pipes on higher performance cars.

Did you not sell her in the end?

Thanks all.
I shall get some tubing and fix this and see what happens - presumably the symptoms fit with this being split Jon? Of course it might not be the only one!
As a test all I did was pull various connections off - dump valve etc (one at a time) and fire 10psi down it and listen. Will that give me some idea?
Heater seems to be functioning ok.
Car is sort of for sale (typically I have had to put someone off from viewing this weekend with this problem) but I really quite like it and end up using it more than the 996, mainly to keep the miles down.
Followed a 991 turbo in this morning. He seemed to want to prove a point by caning it off the lights mind!

Those joining pieces are prone to splitting/perishing - probably more so on a Turbo car. I have just ordered some new ones for my S, mine pressure tested OK, but I replaced them anyway as they looked perished and I was tracking a vac leak/idle issue anyway.

I haven't use silicone tubing on a turbo car for a while, but the last stuff I had I wasn't that impressed with, OK on boost, but when subjected to vacuum the wall didn't seem thick enough to resist collapsing.

When I have my 850 T5 and 850R the general advice from the tuners back then was to replace any small boost/vac lines with Goodyear fuel hose, cheaper than silicone tubing and arguably more suitable.

For balance, I have not seen any of the 'non-collapsing' silicone tubing, but if John is happy to use silcone then it must be up to the job. I'm sticking with the OE hard pipe and have replaced any of the perishable elbows/joiners.

I had intermittent idle issues that I tracked down to a vacuum leak when a hose kept coming off , the only way to cure it with the standard hoses was to use little cable ties on the connections.

+1

I have done that with all my standard vac lines and have had no issues since.

Stuart

Silicone pipes arrived and fitted. Car starts and runs and I'll take it for a spin tomorrow.
A couple of things I wondered:
In the centre of the inlet manifold there is a threaded hole which has nothing screwed into it. Should there be? Its just off to the R in the first pic (but out of shot).
Also there is a blue connector (just in shot) about 2" from the offending cross piece. Does it have a function?
Hopefully tomorrow will go well.

Inlet manifold is for lhd throttle cable set up.

Blue / black thing is a no return valve

Ta. Clears that up. Do these non return things fail? Could cause problems.

Yeah, more been placed on the wrong line or wrong way. Off top off my head I couldn't say.

Tell us how it's set up someone will say if it's right or not

I had an issue with that 3 way joiner recently. One of the hard pipes was constantly falling out of it, causing idle issues and lean running. Did a bodge with some glue whilst awaiting a replacement and the car seemed to run fine - was tuned by my Indy who said the gas results were very good indeed. We'll then it was replaced and the whole car had to be retuned quite dramatically for air and fuel. The 3 way piece looked ok on the outside, but was very compressed on the inside. Something to be aware of perhaps When replacing.

Incidentally, how does the home mechanic best check or adjust air and fuel mix correctly without the diagnostic equipment?