Please help, I知 at my wits-end!

[OZCarrera3]

I intend to replace all gaskets and seals as a matter of course.

I have actually confirmed that the WUR was getting power. I was originally testing it with just the ignition switch turned to the 'On' position. This is not correct. I actually had to start the car and test it then as it only comes on with the engine running. It registered about 10.6 volts. I know it is supposed to be 11.5, but not sure if it was the meter I was using or just the connection I was getting. I am also assuming that a diff of 0.9 volts would not be sufficient to cause any issues.

The reason I decided to get the FD rebuilt was that another Aussie Pelicanite (Gavinlit) had almost exactly the same issues as my car and he too had spent an enormous amount of money and time chasing the problem. Whilst his FD is off being tested (which showed no issues by the way) they decided to put another FD on his car to see what happens. Guess what, solved the problem. Gavin then had his FD rebuilt and put back on the car and he has had no issues since. Therefore I decided to take the same route as a last option.

I still think that this is probably the cause of my problems, although obviously the airbox etc will be a contributing factor. I will however repair/replace the airbox and seals and see what happens.

By the way, should I repair my airbox or replace it with another? I am thinking that repairing would probably only be a short term solution before it cracked again.

[T77911S]

did u have a pop off valve in the air box?

[OZCarrera3]

Yes, there is a pop-off valve and has been for some time

All I can think of is that maybe the airbox took a hit getting the engine out either this time or previously. Also, maybe some inadvertantly used the airbax as a 'hold' when moving the engine about on the trolley. Anything could have happene I guess.

I'll fix the leask and renew all gaskets and see how I go before rebuilding the FD.

[gavinlit]

My path seemed a bit similar to yours in that something was obviously amiss and the easier things were checked & replaced first - such as seals & injectors. In the searching stage it became pretty apparent that many components needed to be replaced (which in your case relates to the airbox). The FD was basically the last of the possible culprits. Who knows - you might get lucky & find it's just the airbox.

[Walt Fricke]

Oz

Don't beat yourself up too much about the cracked air box. My guess is it cracked long ago, most likely due to a backfire. I don't think those cracks could have formed just because you balanced with the air box, or nudged something whilst soving the engine under some pesky part of the chassis. I've done that lots of times with no ill effects - it is not like using a sledge hammer or hoisting the engine by the air box. Someone went in there looking for the cause of a problem, realized that the rather delicate gasket had gotten torn, had no replacement, said "what the hell" and just stuffed things back together. Then came the pop-off valve. Which is interesting, because you have the "improved" cold start injection internal plumbing which was supposed to cure the airbox explosion problem.

Besides, that gasket (unlike the airbox) is not sealing a negative pressure space (if you discount the drag of the air filter). It is upstream of the air flow measuring plate. Its absence is just a potential source of some unfiltered air.

The bigger question is can epoxy or other substances or methods be used to repair the cracks?

Walt

[T77911S]

cracks in the air box will make u run lean. have you tweaked the mixture to make one side that may be leaking air run correct and now the other is too rich?
power to WUR?
did u ever get the control pressures checked?
a lot has been talked about here, can u do a refresh on what u have done?
i think i read that someone else had a bad running problem in the 2-3000 range and it was their coil? go figure.

[OZCarrera3]

The interesting thing about the cracks in the airbox is that the biggest cracks (which open up by about 0.5mm with a little jiggling), are on the same side that the spark plugs are running lean - coincidence? Although I did find that 2 of the Fuel Injector inserts were a little raised on the same side. I have pushed them back in, but they weren't significantly out of place.

As a bit of a refresh, yes, the pressures were tested by both the specialist tuner and Porsche and were found to be within spec. Since then I have also had the ignition checked (Distributor, CDI, leads, etc) by a specialist Porsche 'sparky' here in Brisbane and all have been found to be ok.

I now won't be able to get back to checking the car till after Xmas now, but I plan to re-seal the airbox using a suitable sealant and then see how the car runs.

On the downside, a number of Porsche specialist that I have shown the cracks to don't think this will be the cause of my CIS issues. Failing this, my next (and final) option available is to send the Fuel Distributor away to be rebuilt. I will also have to WUR and Air Regulator (re) checked at the same time

Other than that, I have been investigating my options with regard to going EFI (BitzRacing) or to Carbs (PMO's, Webers) should the above fixes not resolve my problems.