Oh dear

[944Scott]

So now I have the car back I have been able to tinker for the first time since November. Whilst fiiting a new DME temp sender I found this

It turns out the intercooler pipe had been rubbing on a jubilee clip on the coolant pipe below.

 

[Diver944]

That turns out to be great news! You will have had a sizeable boost leak there, so once its fixed say hello to plenty more power [8D]

 

[Kongsodoken]

Worth everyone checking mine was exactly the same just not quite broken through [:-]

 

[944Scott]

I have to say I had not noticed a boost issue until now. The hole is fixed with some expoy metal. I fitted a new dme sensor which has resulted in the car running much smoother, less of a rich mixture smell & a quieter exhaust but I am now suffering with what appears to be a boost issue under load, as soon as I get near to 15 psi its as if the car starts stuttering and shaking. Whats going on ?

 

[Frenchy]

Standard chip set ? if so overboost kicking in.

 

[944Scott]

I was just reading about that. No i'm promaxed level 2, manual mbc cycling valve not in use etc. From what I have been reading it does sound like over boost, I have only driven it two times since getting it back and on the first journey I thought I noticed some small stuttering but now and since changing the dme and fixing the hole (is this just coincidence?) its much worse.

 

[Masher]

This is an observation hoping to prompt a thought from someone else rather than a firm idea... But since the car has been on its side, fluids (water, fuel and oil) have had an opportunity to work their way to places you'd not expect them. Is there any chance a fluid has got into a part of the system that it is not expected to be in? Oil in an air filter for example? Soooo frustrating when a fundamentally fine car is not running just right. Best of luck, Mick

 

[944Scott]

Air filter is as clean as a whistle. I lay awake thinking about this last night and I remember over the past year I must have tweaked the mbc up at least three times. Now i'm no turbo expert but that hole has been growing for some time as the surface is rubbed smooth (although it does not look like it in the picture) so I'm wondering whether my tweaking has been accounting for the leak and now the hole is repaired im making too much boost. Does that sound plausible?

 

[Frenchy]

Yes, though the overboost function will have been removed with the chipset, i would certainly get a boost guage on there to see what it is producing as too much = BANG !

 

[Diver944]

Always difficult to diagnose something like this over a forum, but if you have been turning up the boost to compensate a leak I suggest you turn it back down now the leak is fixed. Could the stuttering and shaking be knock or pre ignition? Both of these can kill an engine very quickly. It would be a good idea to get the boost level set up again safely on a rolling road where the AFR can be measured against the boost level.

 

[944Scott]

Hmmm I have both gauges, problem comes in around 15 psi and my afr reads about 12:5 whereas previously it was about 13:5.

 

[Frenchy]

Now running richer on boost which is fine, 11's is what you need AFR on 18 psi, have you treat her to some new plugs lately, possibly ignition, my car had not been doing too much in the way of miles lately, took her out about 2 weeks ago and gave it some beans when nice and warm, bit of a bang from the back end 9exhaust noise) when coming off boost. Has been tickety boo after some fresh fuel and miles.

 

[944Scott]

Plugs dizzy cap and rotor are three years old and Its currently got some 99 ron in the tank. Googling the problem is doesn't sound unlike a knock type fault. I have ordered a new sensor for good measure and will test and check the wiring to the original at the weekend. As it was running rich I will clean up the plugs and my wideband sensor and give it a general good look over, hopefully its something simple as i'm running out of time before Rutland.

 

[George Elliott]

The hole is fixed with some expoy metal.

Probably OK, but I'd be wondering if that material could ever enter the pipe, the engine would not appreciate it. It wont go wrong on boost anyway with all that positive pressure. [] George 944t

 

[944Scott]

There's a big pudge of it on the back of the hole to make sure it does not happen. Its really quite good stuff as I used it to repair the seated area of a wheel nut when I had to drill one off another car.