O2 sensor and low boost

Mayszak, David A mayszada at bp.com
Wed Jun 26 16:54:03 EDT 2002

Thanks all for the advice.  From your responses, it dosen't sound like the
O2 sensor may be the culprit.  I haven't checked the codes yet, but plan to
next week.  I've taken off the "MM" hose and checked it.  There appears to
be some surface cracking in the crevases, but nothing that looks like it
goes completely through the hose.  The hose I did replace ran from the turbo
bypass valve to the back of the manifold.  I re-routed it along the
passenger side fender and firewall.  I should think the added length
wouldn't be a factor.

I'll try to pressurize the system and continue to look for leaks.
Thanks again

-----Original Message-----
From: Phil Rose [mailto:pjrose at frontiernet.net]
Sent: Wednesday, June 26, 2002 11:12 AM
To: Mayszak, David A
Cc: '200q20v at audifans.com'
Subject: Re: O2 sensor and low boost

At 10:41 AM -0500 6/26/02, Mayszak, David A wrote:
>I'm an "old" newbie in that I've been reading the postings for about a
>but this is my first posting.  I've had my 200 20v for about 10 months now.
>It has always run well, started quickly and idled very consitantly and
>stalled.  However, I've never been able to get it to boost higher than 1.2
>bar.  The Multi function temp sensor was faulty and has been replaced, but
>did not improve the boost.  The wastegate bypass valve is new along with
>frequency valve.  I've also relaced the hose which runs from the WGFV along
>the manifold to the back of the engine

You mean the hose (along the manifold) to the turbo bypass valve? Are
you sure it's well clamped at both ends?

>  and have checked the "Michellin man"

Many other possible sources of leak(s): hose clamps
galore--especially check the several small clamps near/to the ISV.
Also, the connection (pipe) to the intercooler is awkward to check,
but there's a big o-ring that sometimes fails.

>   The plugs are fine and correct. I'm now suspecting the O2 sensor.  My
>questions are; can a faulty O2 sensor result in retarded boost?? What, if
>any other symptoms may a faulty O2 sensor cause?? If the sensor is bad and
>disconnected, would I see a difference in the car's performance??  and the
>present O2 sensor has three leads to it, is this a generic sensor or an OEM

I'm doubtful that O2 sensor is causing low boost. A bad sensor often
causes a slight surging that is felt while you are at constant,
moderate throttle.

The (proper) generic heated sensor would have three leads, but with
crimped or soldered connections somewhere along the wiring harness.
Otherwise it's probably OEM.

Have you checked for any ECU codes????


Phil Rose
Rochester, NY
mailto:pjrose at frontiernet.net

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