BPV was: CEL possible O2 sensor 1.6 bar now 1.3 SOLVED?

SuffolkD at aol.com SuffolkD at aol.com
Tue Sep 7 00:19:55 EDT 2004

 Lister(s): 200 20V 3B

I took Roy's advice and Chris Millers' and persued air leaks.
The first was obvious.  The spliced line from the BPV to the back of the 
engine area was broken / slipped apart.  this was tucked under the front support 
brace where the hood latches down.

Replacing that with fuel line got me to at least 1.5 bar. (Chipped)
1.6 was had for long periods of time in fourth gear too.
The only other thing I tinkered with was the ISV,  only partial pumbing 
disassembly and carb cleaner into it to disolve any gunk affecting the seal/seat of 
the valve.

Having the car chipped led to a major rush compared to 1.3 bar.  even with 
the MFTS replaced the temp gauge reads low or intermittent.

Interesting sidebar for 20V'ers
The Bosch bypass valve 710N:  Leaks air past it around 7-8 psi when new.
Replacement I had put in 7,000 miles ago was clean inside and leaked at 8 PSI.
The old one I replaced last year (kept as spare) leaked at 4 PSI

Chester  provided the pressure tester and Art from Salisbury Motor cars in NY 
had a new BPV to lend for the test.  Phil watched too.

Thanks for the help.
-Scott by BOSTON
> >
> > I'm prepping for a track event and seem to be slipping backwards.
> >
> > We chased down some vacuum leaks and the car ran to 1.6 bar (93) 
> > octane.
> > Now the car has hesitation and when it does, it only pulls 1.2 / 3
> > bar.........where I started before chasing vacuum leaks.............
> >
> > Now the ChkEngLight has come on. and its on quite a bit now. (Today)
> > Vag-Com car tonight  DTC is :
> > 00537 - Lambda Oxy sensor regulation 08-00 control limit surpassed.
> > Now I just put this new $130 full cord & plug one (I wanted it) in 
> > last Aug.
> > ~7,000 miles ago.  (Car sat all winter)
> >
> > Using the measuring blocks on Vag-Com Field 8 is a value which the 
> > book Vol 1
> > pg 24-90-2 says: "MUST fluctuate around an average of 128.  Value is 
> > 160.
> >
> > So I'm leaning towards the O2 sensor bad............
> >
> Disclaimer: I have no personal experience with the 3b, but I do have 
> experience with other Motronic systems and it's variants.
> I think that you have to get away from the idea that a component fails 
> and the computer tells you which component it is. <<<SNIP>>>
 A closed loop o2 sensor system is something of an add on 
> feature to the basic airflow or load based stored  fuel map. Because a 
> standard narrow band o2 sensor is only accurate at indicating rich or 
> lean, most systems cycle between rich/lean a few times a second in 
> order to reach an average of 14.7. The fact that your reading is stuck 
> at one value that is well out of range says that the afr is way outside 
> the range for which the o2 sensor and ecu can compensate for when the 
> conditions are met for closed loop mode.
> Roy Wendell

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