Luis de Prat

Just replaced the Cycling Valve, Throttle Position Sensor and Idle Stabilizer Valve on my completely stock 951.

The previous scenario was an on-again / off-again boost situation which would change by shutting the car off and back on again, apparently resetting something.

This is no longer the case, as the boost comes on consistently, regardless of whether I shut the engine off or not. However, I'm not maxing out at the 2 mark on the stock gauge like I used to. When the car is on boost, the needle sticks at a couple of marks below the 2 while the engine continues to climb to redline.

What could be causing this? TIA

special tool

Would you estimate your boost to be about 11 psi?
If so, this is correct - you have fixed your car!

Luis de Prat

Hmm. So you don't think I may have a leak somewhere? Why would the (it's junk, I know) stock gauge read 2 before and not anymore? Thanks again!

special tool

I don't know, you didn't answer my question.

Luis de Prat

Admittedly, I should check the pressure with an aftermarket gauge but I don't have one.

The reading I'm getting is 1.85 bar on the stock gauge, which is way too high to be accurate (26 psi) but the same gauge used to read 2 bar before I had this on-and-off boost problem, so I now suspect I have a leak somewhere. BOV, perhaps?

Chris White

you are really seeing .85 of boost (or 1.85 absolute)
All is well - enjoy it!

special tool

That is almost EXACTLY spec for your car.
Perfect!

Luis de Prat

Thanks to both of you. It things are finally normal, then it seems like forever since I started chasing this on-and-off boost problem.

Still, why would the reading be differently now from when the car was running normal before and hitting the 2 mark? Could this be caused by the failing Cycling Valve before I replaced it?

special tool

Yes, if you had a cracked line to the wastegate, broken cycle valve nipple, etc.

Luis de Prat

Got it. My curiosity is now satisfied.

ausgeflippt951

you're a lucky sumbitch. I can't even get 2 bar when I clamp the WG-CV vac hose. Unclamped I've been cruising at 1.25...when I get back from Thailand i plan on replacing all vac lines and whatnot...sigh.

had this problem w/ the car since i bought it...

Luis de Prat

Hey, my CV was bad. Did the TPS while I was at it, but the culprit seems to have been the CV nonetheless.

special tool

Yours has probably a fault code stored.

ausgeflippt951

really? is there a way to fix it? The car is stock and i've done the following to diagnose the problem w/ extremely minimal results:

-replaced CV
-reinstalled intake plumbing and checked all air/vac lines
-shimmed WG +5mm (this allowed my car to now pull 1.23 bar vs the previous 1.19 i was getting beforehand)
-made the cheapy LR blink code tester and came up w/ zero codes (er, rather, it didn't blink at all, and yes, the LED does work)


So what do I do?

facboy

check the klr connection in the footwell. i could only get about 1.85psi of boost and it was caused by the klr connection being 'too loose' - which is crazy to be honest, it was done up pretty tight with a straight-drive socket (admittedly fairly small), but apparently that doesn't cut it. i used a ratchet on it and got another half-turn or so out of it, and that fixed the problem. i was very surprised .