tommye

Took the 951 cab out yesterday for the first time since ages, spring is here and there is finally enough friction between tires and pavement to be able to build boost!!!

In order to fix the occasional overboost cut-out problem, I’ve done the following in the meantime:

Pressure-tested the intake system (filter+AFM box out, 1 bar of air in through adapter, listen for leaks) and noticed slight leaks in the idle regulator and in the throttle housing.

Checked for leaks in the WG control-line – ok, no leaks.

Removed manifold and replaced the following with new:
Several vacuum lines, most of the clamps (Many of the vacuum/pressure lines were loose fitting), idle regulator, CV, intake gaskets, injector seals, small fuel line on fuelrail, distributor cap and rotor.

Installed new seals in the TB using Bruce:s kit.

Removed and thoroughly cleaned out the intercooler – there was a fair amount of oil in there. Rinsed it several times with gasoline.

Cleaned the injectors with compressed air and carb cleaner using a battery to switch open the injector.

Checked resistance in AFM, TPS and temp sensors. All ok.

Before completing installation, I decided to pressure test the intake again, and guess what – the brand new original CV is leaking - clearly audible and it can easily be felt with the hand

Since almost everything was done, I quickly installed the rest and made a quick test drive. Everything seems normal until I open it up - I only get 1.6 bar max. boost.
So, as you can guess I was quite disappointed.

So my questions (before removing the manifold again) are:

A leaky CV, wouldn’t that INCREASE boost instead since some of the pressure is bled off and not reaching the WG?

Another possibility would be that my old CV is faulty and gives too high boost (also explaining the overboost cut-out:s). The fact that I have 1.6 bar now (instead of 1.8 before) would then be explained by something completely different.

Has anyone succeded in replacing CV with manifold installed ?

I’m thinking of reinstalling the old CV just to see what happens. It’s probably ok, I just replaced since I was in there.

A always, any help is greatly appreciated !!

Tommy

hally

maybe you may have a stronger boost signal going to the KLR now (which controls the cycling valve)
just a guess. 0.6 bar boost if accurate is a bit low for stock. Maybe your wastegate spring is weak and could use some shims.

hosrom_951

1) Did you delete the venturi, replaced ALL or just replaced "some" vacuum hoses?

2) Are you sure you installed the Idle Actuator (ISV) with the correct orientation (there is an arrow on the ISV that should point to the "short" hose on the intake).

BTW, did you replace the intake manifold gaskets?

tommye

Hally,
I had 1.8 bar and occasional overboost cutouts right before the "fix" so the WG is ok. Car is bone stock. My SOP dyno can also tell the difference between 1.6 and 1.8.
Stronger boost signal to the KLR...hmmmm.....


Hosrom,
No venturi on the -91 !
Hoses are in very good condition, thoroughly inspected and pressure checked.
Idle stabilizer is correctly installed. Gaskets replaced.

I'm just thinking about what to do next. It annoys me to have to take the manifold off again.

Cheers,
Tommy

Sami951

1.6 is what I was getting with one of those tiny plastic hoses that go to CBV, fuel pressure regulator and whatnot disconnected. It was a b*tch to find... I'd double-check them all if I were you.

The stabilizer "leak" shouldn't really affect anything, as it's plumbed between the intake manifold and the ic-to-throttle body tube ... so on boost, there really isn't much pressure difference anyway.

tommye

Sami,
It is not the idle stabilizer that leaks - I replaced that with a new one. It is the Cycling Valve (which I also replaced by a new one, perkele)......

Tommy

J Chen

What about your turbo ? Try to spin with
your fingers to see if it spins freely.
Also do a visual check to see if the blades
are o.k.

jimbo1111

You can change the cycling valve with the intake on. I have. Not easy though. Since it's leaking I would suspect that it's the problem. Not enough air to the waste gate to hold it closed.

fast951

Jimbo, The cycling valve routes air to the stock WG to open it NOT to keep it close!

Tommye, do you have any exhaust leaks (headers, X-over pipe)? How clean is your air filter? Inspect the turbo...

tommye

Turbo spins and looks just fine. No audible exhaust leaks. And...it was doing 1.8 just before replacing all those parts.
As John points out, less air towards the WG would mean more boost...
Tommy

fast951

Are you checking boost on the stock gauge? Might want to use an aftermarket one.

J Chen

What about your bud dyno ? Does the accel
feel as strong as before ? Fast could be right
about this.

jimbo1111

Sorry. I would still suspect the cv because of the leaking your getting.

fast951

Please explain!

jimbo1111

If he can feel the air with his hand could you imagine when on boost how much he is loosing. If the plunger is bad in the cv it could also route air into the negative side of the intake. There are 3 connections on the cv. banjo bolt, wastegate and intake boot. Common sense. It has to be replaced anyway. It may just solve his problem. The horse goes before the cart. Next thing I'm going to hear is that he needs a new 3.0 liter motor.