98' S70GLT SAS Delete mileage penalty?

macs70GLT · Post by **macs70GLT** » 06 Aug 2014, 08:36

I recently did the SAS delete, splicing the diode into the wire bundle under the module.

First tank of gas after that mileage was down to 18.5 mpg (I typically get ~ 21 to 22). The fuel gauge showed fuller on this one fillup - likely just a difference in pump at the station.

Have been using 89 octane gas.

I've now driven 986 miles, 50.4 gallons for overall 19.56 mpg.

Is this typical after SAS delete??

If so I'll remove the diode & live with the engine light for the extra savings.

Thanks for any inputs

Mike

Post by **erikv11** » 06 Aug 2014, 09:05

'Tis not typical, I have not heard of or experienced that after SAS delete.

What is the vintage of the oxygen sensors? Can you put an OBD scanner on there and see what the LTFT (long term fuel trim) is?

Out of curiosity, did you disable/remove the SAS parts, or just leave them all in place?

macs70GLT · Post by **macs70GLT** » 06 Aug 2014, 11:55

erikv11 wrote:'Tis not typical, I have not heard of or experienced that after SAS delete.

What is the vintage of the oxygen sensors? Can you put an OBD scanner on there and see what the LTFT (long term fuel trim) is?
Out of curiosity, did you disable/remove the SAS parts, or just leave them all in place?

I have replaced one of the Oxy Sensors, probably 40K miles ago (don't recall which but can check). The other Oxy Sensor might be original - if so 220K miles.
I have a Scan Gauge, will have to look up how to check Long Term Fuel.

I only added the diode, have not removed anything.

Post by **erikv11** » 06 Aug 2014, 12:06

If the 220k sensor is the front one that could (or maybe even would) be it, coincidence maybe.

Might as well unplug the air pump and cap off the vacuum line to the SAS valve, maybe there is a small vac leak.

macs70GLT · Post by **macs70GLT** » 06 Aug 2014, 13:04

Thanks

I'm heading out of town tomorrow so I'll unplug the pump & cap off the SAS valve before the trip & see how the mileage it.

I'll also post the Oxy Sensor LTFT.

Which SAS valve - Is it the SAS check valve (B&W up by radiator fan), or the SAS Air Injection Valve back by the Turbo?

Mike

Post by **erikv11** » 06 Aug 2014, 17:08

A vacuum line runs from the SAS injection valve back by the turbo, to the SAS solenoid valve up at the rad fan, then continues through a check valve to the vacuum tree. Disconnect the line at the tree, and cap off the nipple there. Then the whole vac line path can be removed, from both items.

The SAS solenoid valve up at the rad fan has to remain plugged in to its electrical connector, but the vacuum line can come off of it. The SAS valve can be removed, along with the pump. You can also unplug the pump for now.

macs70GLT · Post by **macs70GLT** » 11 Aug 2014, 13:12

The first leg of my trip ~ 100 mi, I left the car as it was. Going up Snogualmie pass. After camping up there I capped off the vacuum line at the tree and on the line for the return trip.

Mileage stayed about the same going up & returning, both about 23.4 mpg or so. I'm doing a few other tasks which may also affect mileage like replaced the pcv system over the weekend after that trip. In the past I usually get 26+ on the highway for trips, so mileage is still down.

Once I'm done with these other jobs I'm planning to disconnect the SAS delete diode (& reconnect vac lines) then I'll report back on any change in mileage.

btw, I wasn't able to check voltage on the O2 sensors with my Scan Guage II; if one is failing wouldn't it set a code?

Thanks

Mike