Luis de Prat

What to check? Just had the clutch replaced (all stock, new turbo S parts), flywheel resurfaced, new fork, etc. but the boost just isn't there.

Revs just climb and climb, and the car drives strongly with the new clutch, but there's no "turbo kick."

Can't hear the wastegate growling, either. Car has about 67K miles, no mods.

tommye

Welcome to the club.....
Seriously, what does the boost gauge tell you ?


Tommy

pikey7

Has someone dslodged a vacuum line? (Mike goes for the easy suggestion and withdraws gracefully.....)

Thom

Try the gasket between the X-over pipe and the C-shaped tube linking to the wastegate.
Did you make sure the exhaust gaskets that were pulled off were all replaced ?

David Floyd

Check the hose to wastegate

Luis de Prat

My thoughts, precisely!

I take it I'll need to get under the car to do this?

Also, last time I had a "no boost" problem, I think I corrected it by replacing the BOV with a 993 part, but then again maybe I wasn't holding the pedal down long enough for the boost to kick in, since I only had the car a short time.

Now the (stock) boost gauge only reads about 2 or 3 notches past the middle (1) mark and not all the way to the end (2) mark like it does when boost is working.

FWIW, the stock clutch came out well worn, but intact, with ALL the springs in place, large and small.

tommye

Hang on a second, if you have a problem with the WG-control hose, clogged, broken or simply disconnected, you will get TOO MUCH boost. It is actually the boost pressure reaching the WG via the Cycling Valve that LIMITS boost.....

Did your car behave this way already when you picked it up from the clutch replacement ? If yes, one has to assume that they forgot or messed something up.

2 or 3 notches, that is 1.4 to 1.6 bar (right?). This is not the "limp-home" 1.2 bar mode which excludes many things....
My best guess would be an exhaust leak which simply just limits max. boost. You have to remove the exhaust to get to the clutch.........
Is there any difference in exhaust noise ???

Best of luck !
Tommy

PS. Good to hear about a 14-year old Turbo clutch with intact springs !

special tool

Luis - THIS is the classic cycle-valve failure. Check it out, man.

Luis de Prat

Thanks for all the suggestions. There was already a non-boost situation when I took the car to have the clutch replaced, although the clutch was definitely slipping and no longer does.

Tommy, the idle is extremely smooth and stable. So is acceleration in the car, and the clutch obviously feels grippy and crisp as it should after all the parts I've replaced

What beats me is how the engine revs just climb and climb all the way to redline and the boost never kicks in like it used to. Before, I would floor the accelerator and at around 4K revs the boost would kick in and the revs would halt momentarily while the car shot forward. Doesn't do this anymore.

Please "edumacate" me on the cycling valve. I assume I'll have to remove the intake manifold to reach it, etc.? This car has "only" 67K miles.

special tool

It is the electric solenoid which controls boost. It is a small plastic cylinder with a brown top and tan sides. It has 3 air ports on the side, and a 2-prong electrical connector on top. It is between and below intake runners 3 and 4. U esto uxo de puta no vale para nada.

Weissach Vampire

Try to disconnect the connector to the Throttle Position Switch, Spray something like CRC 5-56 in there an put it back. If you have oxide in this connector Motronic detects something is wrong and will limit boost to around 0.2 bar.

Had the same problem with my car when I bought it, I found the problem with help from the blink code, quite handy....

Good luck.

special tool

actually - yeah Luis - check the cycle valve. I just saw that you did the clutch. The mechanic removed the wastegate line, and probably cracked the plastic nipple. They are WAY too easy to break.

If your idle is smooth and stable below 1000 RPM, you do not have any fault code problems.

Weissach Vampire

Try my tip anyway, my car ran just fine except lack of turbopunch, I even bought the car in this condition thinking everything was ok (had no prior experience of 944 Turbos so I didn´t know what to expect in terms of power, realised later..).

special tool

Yes, I agree - does not hurt to try.

tommye

Weissach Vampire,
he has 0.4 - 0.6 bars (right Luis?) - this would normally exclude Throttle Position Sensor. If TPS is bad, boost should be 0.2 ("limp-home" mode) plus associated blink-code.

Special tool,
If the WG-line or nipple is broken, boost should increase, not decrease.
However, I agree that the CV itself could be bad.

So, if the problem was there before the clutch swap......the standard check would be to tightly clamp (completely block) the WG-line and see if boost goes up to normal - just like many people here have done. Be careful not to overboost though - let go of the accelerator as soon as boost reaches 0.8 (1.8 on meter).
The WG-line is attached to the rearmost connector of the CV and goes down behind engine to the WG. A bit tight to get to but feasible.

If boost goes up - problem is in the boost control circuit ry (KLR, CV, small vacuum lines etc.)
If boost stays low - boost is limited by the turbo itself, bad WG, leaky exhaust, leaky intake connections etc.

Tommy