MyMachV

I am officially experiencing information overload after reading all the threads and DIYs on diagnosing low boost issues I am asking for everyone's help.

I am making no more than 5 lbs of boost and have done the following:
- Replaced the J Boot
- Found a loose clamp at the IC and tightened it
- Checked all vac lines for visible cracks
- Installed an aftermarket boost gauge
- Got the 3-3 error when running the test, per LR site DIY, then...
- Replaced the CV and corresponding vac lines

IF I clamp the rear line off the CV I get lots of boost.

What is my next logical step?

If anyone in the Philly/South NJ area loves tinkering with 951s and wants a new friend consider me

xsboost90

someone still has a cycling valve?! sounds like your wastegate is working, somewhere forward of the cv you have a leak. Not sure if the recirculation valve would do that, but you can vac test it anyway. If it is let me know i have a billet evo recirc valve fs. Most just ditch the cv and route a boost controler between the intercooler line and the wastegate- ahh- i have a boost enhancer you can put in there if you want...pm me.

Ky944TurboNewbie

I feel your pain. I battled an over boost protection issue kicking in for a couple of years before finally tracking it down. You need to pressurize the intake system to rule out leaks. Van has a nice video about how he did it on his.




Another option it to buy or make a tool to connect to the intake and pressurize there.



Here is the Arnnworx link to buy this tool.

http://www.arnnworx.com/catalog/inde...eee2187855ae9b

This is the easiest and one of the cheapest things to do first. My homemade tool cost less than $5 for a PVC cap and a valve stem from my local auto parts store. I didn't have a compressor that could shoot pressurized air at 10 lbs, but I was able to find plenty of issues just using a bicycle pump. It would have been much more effective and easier with a compressor though.

I assume you already read the 951 faq on Clarks Garage. But if you haven't:

"Diagnostic Suggestions: Clamp off the line from the cycling valve to the wastegate and drive the car. This will close the wastegate and direct all the exhaust to the exhaust turbine. Now drive the car but do NOT fully depress the throttle. Just go over 3,000 rpm to see if the turbo boost is working. (If it is and you depress the accelerator a lot then the turbo could spin too fast and over-boost the engine causing damage.) If the car then boosts OK it means that the cycling valve and line are where the problem lies. The wastegate is not being controlled properly. This could mean that the cycling valve is being given bad information due to a faulty DME, knock sensor or 'control units' or is faulty itself.

If the car doesn't boost properly then look for:

A mechanical problem with the turbo
A leak or other problem in the air intake system
The wastegate sticking open
A leak in the exhaust system
Other mechanical problems
Engine computer problems

These checks should point you in the right direction."

Michael

SD Porsche Fan

You can build your own boost tester out of common parts found in the plumbing dept. of your favorite hardware or home improvement store.

I attached to the hard pipe coming off the turbo. That way you avoid pressurizing systems that were only meant to run under vacuum.

This also eliminates the need to take off the AFM, air filter box, etc. If you want to test for vacuum leaks that is a different process IMO.

Edit - The Arnnworks tester at the location pictured on the previous post bypasses the CV and anything else that runs off the banjo bolt. If you're leak is there you'd miss it with that set up.