Boost problem

[adrial]

It only does it the first few times I floor it, and doesn't do it at partial boost (say .2 or .4 bar).
Last night it did it the first few times...just now it did it only the first time.
Now to explain what "it" is...It's not like hitting a brick wall...and when I did look down at the boost gauge it was showing 2 bar (1 bar boost...). I'm not positive if at the moment I looked down the car was doing the boost problem. It seems to stop accelerating momentarily. However it could be accelerating slowly...compared to on boost acceleration its not accelerating. It used to last for a split second...now lasts for a second or 2 I think. Again...it only does it the first few times I hit full boost...after that the car's fine.

The history of this problem is that my brother experienced it when we first got the car...when I drove it, it only did it once and that time very mildly. When the car was brought to the mech to have the belts replaced, the mech noted this boost problem. He thought it was the overboost protection which I know isn't true because the car is chipped and he knew that. Just recently (past week) the car has started doing it every time I get on boost for the first time in that drive. After it did it the first time (recently), I tightened up all the hose clamps...made no difference.

I'm fairly sure the problem is a vacumn line/some sort of a hose problem...but which one is the question? I can hear a hissing with the hood open and the car running, is that normal? It's had this boost problem ever since I got the car in June. If that hissing sound isn't normal...I would assume a mechanics stethescope would allow me to pinpoint the leak? It's probably time to replace all the vacum lines anyway...so what brand/diameter hosing should I use? I've read on here that the inner diameter of the hose is very important, as well as the thickness of the wall to prevent bulging (increasing the I/D...) Is there a diagram anywhere showing all the lines?

thanks,
Adrial

[Pilot_951S]

I don't think it is possible for the car to not have any power when it is under full boost.

Having said that you need to pay very careful attention to the power problem. If the boost is actually dropping (instead of staying at 2 bar like you said) off it could be caused by any number of things but it is likey electronic since the condition is intermittent.

There are several things I would check in no particular order

I would find a shop with a smoke machine to pressurize the intake system and the exhaust system to look for any air leaks.

Get a hold of the test relay so that you can see if the KLR brain has any codes. This only works when you have expereined the problem and you have not yet turned the car off, the memory clears when you shut off the ignition.

Inspect the spark plugs, ignition wires, coil, distribtutor cap, and rotor for wear and proper operation.

Test for fuel pressure

Test for injector pulse signal

Inspect the injectors

Replace the Throttle position sensor with a test unit

Replace the air flow meter with a test unit

Replace the KLR and motronic brains with a test unit

I'm sure I can think of something else to check but that should be enough to get you in trouble.

[adrial]

How do I go about checking spark plug wires? Check for arcing with the hood open in the dark?

thanks

[Pilot_951S]

Sometimes that works, I usually get a spray bottle full of water (which I dubiously label as "ignition wire tester") and mist it on the wires and the distributor cap. If it is going to arc it will arc in the presence of water.

[DennisR_944]

Go Here and D/L the .pdf file that has the blink codes for your DME and see what the problem really is. Good luck.

[adrial]

Many thanks, I'll do that tomorow assuming the roads are dry.



--Adrial

[adrial]

Problem solved! (I think)
One test drive may be a bit too early to tell, but I did the exact same
thing I did the night that it gave me problems and it didn't give me any
problems this time.

I replaced the plugs and tested the plug wires for arcing. (ran car when
dark out and then misted with water)

All is good (so far) in the wonderful world of Porsche!

There's a pic of the tips of the spark plugs at:
http://members.rennlist.com/adrial/spark%20plug4.jpg
The old plugs were platinum's, I replaced them with coppers...

thanks!!!