Problem using LM1- need advice

[mmasse]

Last weekend I installed a friend's LM1 meter on my car.

I did a run for testing, and everything was going great, it looked like my engine was running very close to the ideal 14.7 value, but at one point the LM1 started to provide strange data: AFR above 21.

My friend mentioned that the possible cause is that the LM1 sensor became too hot, because it was attached too close to the headers.

I have a '76 911 with a '97 993 Vario OBD1 engine and I am running a flowmaster muffler with stock 993 HEs. The oxygen sensor bank is in deed very close to the header's outlet . I have a connector for O2 sensor on each side, but since my engine is an OBD1 I only use one. So, I connected the LM1 sensor to the other muffler inlet.

My questions are:

Is this a potential cause for the bad readings of the LM1?

If that's the case, wouldn't that also affect the 02 sensor and send bad info to the ECU?


Thanks

Mario

[cnavarro]

Was the lean reading off throttle? Over-run for emissions/fuel economy maybe?

[mmasse]

No, actually after that moment readings were above 20 almost all the time, regardlesss of RPM

[cnavarro]

Were you using the exhaust sniffer venturi clamp or was this off a permanently installed sensor? Any exhaust leaks or intake leaks? That would be where I would look first.

[mmasse]

I was on a O2 sensor bank on the inlet of the muffler.

The problem is that it started after a while after it was installed, since during some time the readings were fine, including some hard driving

[cnavarro]

Have you tried to recalibrate it?