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200tq boost...FIXED! (I think)
I finally got around to looking at all the plumbing under the hood of
my '91 200q. I pulled off and checked the intercooler-to-intake hose,
the wastegate frequency valve, and the turbo-bypass valve. Everything
seemed in order, but I did replace a couple of small hose clamps whose
screw heads were sort of mangled. No leaks found. Hmm...
Went looking at the vacuum hoses. All seemed tight and no splits.
Then I noticed that when I pulled on one end of the vacuum hose going
down to the turbo bypass valve, the other end didn't move(!). Oh, oh.
It turns out that this hose runs behind the heat shield between the
wastegate and the intake plumbing, and the heat had incinerated about
2 inches of this hose. I spliced in some new vacuum hose using using
some small copper tubing as splices and took the car out for a spin.
Wow! I can hit 1.8 bar with no effort now. It's amazing to think
that I've been driving around for a year with this hose leaking like a
sieve. This also seems to have fixed an intermittent idle problem I
was having. So, all in all, a good return on a couple of hours work.
I'm thinking of replacing the section of hose which runs along that
heat shield with stainless steel vacuum tubing, if I can find some
scrap here at work.
But now I notice another problem...when I approach maximum boost levels
quickly, the car seems to "cut out" or stutter. I thought it might be
due to the 89 octane fuel, so I filled up with 93 octane. The
problem is still there. Am I hitting the boost limiter and cutting
off the fuel pump? Do I still have a leak (under pressure) to deal
with? Is my wastegate frequency valve doing funny things trying to
modulate the wastegate?
Help me out here guys!