[Diy_efi] Post 4-Wire O2 Sensor Swap Observations...

[David Cooley]

Popping on decel is from lean, not rich...
And if you had an exhaust leak before the O2, it may read lean, but mileage
would go down the toilet as it would be richening the mixture up to
compensate.


> -----Original Message-----
> From: diy_efi-bounces at diy-efi.org 
> [mailto:diy_efi-bounces at diy-efi.org] On Behalf Of Mike Frels
> Sent: Thursday, April 21, 2005 10:37 PM
> To: diy_efi at diy-efi.org
> Subject: RE: [Diy_efi] Post 4-Wire O2 Sensor Swap Observations...
> 
> The O2 sensor swap was in *preparation* for the headers. They 
> are still up in the attic waiting for a couple of days 
> opening in my schedule to justify the vehicle downtime for 
> the install.
> 
> As far as the lean condition I am convinced I still have an 
> leak somewhere allowing oxygen into the exhaust before the 
> sensor. The sensor says lean but the hard starts with the 
> smell of raw gasoline afterwards, the missing while idling, 
> and the slight popping on deceleration tell me I am much 
> fatter. Fuel that is...
> 
> Mike
> 
> -----Original Message-----
> From: David Cooley <n5xmt at bellsouth.net>
> Sent: Apr 21, 2005 4:22 PM
> To: 'Mike Frels' <mfrels at ix.netcom.com>, diy_efi at diy-efi.org
> Subject: RE: [Diy_efi] Post 4-Wire O2 Sensor Swap Observations...
> 
> Don't see anything contradictory or wrong... You increased 
> the efficiency of the engine with headers, so now are 
> slightly leaner than before, being lean increases MPG...  If 
> you bump up base Fuel pressure 2-3 PSI, it will bring the 
> BLM's down, but mileage will probably stay up.
> 
> 
> > -----Original Message-----
> > From: diy_efi-bounces at diy-efi.org
> > [mailto:diy_efi-bounces at diy-efi.org] On Behalf Of Mike Frels
> > Sent: Thursday, April 21, 2005 8:54 AM
> > To: diy_efi at diy-efi.org; gmecm at diy-efi.org; 
> third-gen at lists.f-body.org
> > Subject: [Diy_efi] Post 4-Wire O2 Sensor Swap Observations...
> > 
> > About a month ago as part of preparation for my header install I 
> > swapped out my single wire O2 sensor for a four wire AFS97 from a 
> > fourth gen F-body. I wired the heater in via a relay to hot at all 
> > times in the back of the fuse block and grounded via the 
> A.I.R. Port 
> > Solenoid ground line. The sensor I gounded to the back of 
> the diver's 
> > side head. Since the the swap I noticed two what I consider 
> > contradictory results. My BLMs went up between 5 and 10 to 
> what were 
> > already lean ranges. My idle was around 145 before and now 
> it's up to 
> > 150. Same approximate changes in all my easy driving ranges. The 
> > second nice but puzzling change has been my gas mileage. Previously 
> > with my not yet properly tuned Vortec headed 350 I was 
> getting 15-17 
> > mpg for all driving types. Now I get 17-18 mpg stop and go short 
> > distance driving and low 20s highway. Why does this not 
> make sense to 
> > me?
> > 
> > FWI one of the main reasons for wanting to get the headers 
> on before 
> > getting the tuning right is tuning ability. In the passenger side 
> > collector I have added a bung which will allow me to use a 
> wide band 
> > O2 sensor so I can see whats really going on.
> > 
> > Mike
> > '86 MAP TPI Z28
> 
> 
> 
> _______________________________________________
> Diy_efi mailing list
> Diy_efi at diy-efi.org
> http://lists.diy-efi.org/mailman/listinfo/diy_efi
>