I just replaced the cycling valve on my 951 with a new unit from Porsche, only to break a vacuum check valve that I'm still waiting on from the dealer parts counter...

At any rate, I'm now not getting any boost at all which I assume is due to the vacuum leak.

I'm hoping that when I replace the check valve everything will be back to normal but am still wondering whether the on/off boost situation I was having before may have been due to a bad KLR chip, as was suggested in someone's account of an identical scenario in the Clark's Garage 951 FAQ.

Is it possible to just replace the KLR chip?

TIA

 

Since the CV is new, make sure the electrical connection to the top of the CV is not damaged.
Yes, you can change the KLR chip, very simple process. I assume you have the K26/8 turbo, if so, you can use the 951S KLR chip.

Have you manually tested the boost Wastegate to make sure it makes boost? You disconnect or pinch the hose going down to the WG. The car should boost! WARNING - do this for a short test, you will overboost!!! You just want to make 7-8psi then stop the test.

 

Everything is stock from MY 1991. Can I perform this test regardless of the vacuum leak? Thanks.

 

It depends on the size of the leak. You can plug the leak for a simple test.

 

it would have to be a *massive* leak for you to get 0 boost. if you're talking about the little blue check valve, i kinda doubt that that would leak enough.

 

OK, I just pinched the hose from the CV to the wastegate and got boost every time. Does this mean my brand new CV from Porsche is defective? Do I need to replace the KLR chip? Thanks.

 

Bump

 

Im no expert but it seems like a leak somewhere before the line to the wg. What vacuum pressure are you getting at idle?

 

The KLR + CV control the boost. Testing the CV is possible, but you need a scope. You might be able to wie a LED at the CV connection to see if it lights up etc.. I have not used the LED.
The KLR, it's easy to replace the chip. I have seen bad KLR chips causing all sort of issues. The data on the chip somehow got corrupted, not sure if this is the case here.

 

Luis,
in the area where CV is located are a lot of small vacuum lines; those black nylon ones. Check out all of them are attached as thy should. They can easily pop of especially when you change CV.
If KLR chip is corrupted it either work or not. I have never heard that code it self can change if we are talking about Eprom type of device

 

Thanks for all the replies!

Olli, I know for a fact that I have a vacuum leak due to a broken check valve that I'm still waiting on from Porsche. I also need a new 4-way hose connector for the little lines that are banjo bolted to the intake manifold.

As soon as I fix the vacuum leak I'll know for sure whether that's the problem.

About the CV, it's brand new but before installation I noticed that I could slightly blow air through it. Is this normal, or is the CV defective?

 

The CV is just a little flapper valve with with one intake from the banjo bolt and two outlets, one to the wastegate and one back to the intake side. The flapper defaults (without power) to open allowing all boost pressure to the wastegate so yes you should be able to blow through it before installation. I would double check the electrical power to the CV as John suggested and I would verify the line from the banjo bolt is on the inlet. If its swapped with the return that could be causing your problem also. Good luck.

 

Have you taken a blink tester to the car? That should blink if anything is wrong (KLR, DME, etc).

Also, make sure you can make truly UNLIMITED boost. I clamped the line between the CV and WG and thought I was getting unltd boost, where in reality I can't get past 1.85 bar on the stock gauge (I would stop accelerating when I'd hit 1.8 or so; it's OK to run it up to 2).

I've done everything I can think of; perhaps you are in a similar boat.

 

OK, now I'm getting boost again consistently, without having to restart the car.

However, it's NOT unlimited boost. Just like ausgeflippt951, I'm getting a reading close to the 2 mark on the stock gauge, but not all the way up to 2 like before.

The timing belt is being retensioned today, but I have a feeling that won't make any difference other than giving me peace of mind.

What should I look for now?