Getting 8.5 mpg need help

[swathdiver]

Swap downstream O2 sensors then make a deal with GotExhaust for a new Y-pipe and cats.

 

[BlueCollarTahoe]

gonna swap out the downstream sensor on b2 since b1 was already swapped. save up for that ypipe and cat. i got to fix this emissions code before september. i got a bad feeling its coming from the fuel pump assembly.

 

[BlueCollarTahoe]

So just so I'm clear the b2 downstream is what looks off on the graph right? Ordered the new one this morning

 

[BlueCollarTahoe]

hopefully will be changing out tomrrow. wish me luck. i just put 21 dollars of 87 oct gas/7 gallons at exxon and the EST miles was 35 miles till empty.

 

[swathdiver]

I didn't figure the sensor was bad, I figure the cat is bad. You are wanting to be very thorough so that is why I suggest swapping sensors, if you get the same reading on that side, you know its the cat. If the reading moves to the other side, its the sensor.

GMT900s have different PNs for upper and lower sensors. GMT800 have all four of the same PN# correct?

 

[JollyRoger01]

If the cat is working properly the rear O2s should be half of the max min of what the upstream sensors are doing. Typically in the 400mV range. Uppers will constantly switch. If the rears mimic the uppers on a graph, the cats have failed. Hotter the cat temp the tighter the graph will be.

 

[JollyRoger01]

I had a death in the family so I've been away. Sorry for the late reply.

 

[BlueCollarTahoe]

If the cat is working properly the rear O2s should be half of the max min of what the upstream sensors are doing. Typically in the 400mV range. Uppers will constantly switch. If the rears mimic the uppers on a graph, the cats have failed. Hotter the cat temp the tighter the graph will be.

I had a death in the family so I've been away. Sorry for the late reply.

Sorry for your lost.

I posted the graphs of the 02 sensors at 2k rpm. I was driving yesterday highway speeds and the upstream were jumping downstreams were steady. I hacent changed the downstream sensor on b2. Now today...ran a smoke test for thr evapcode 0455 large leak...folloeing the smoke we foubd a cloud coming from the fuel pump.

 

[HiHoeSilver]

Sorry for your lost.

I posted the graphs of the 02 sensors at 2k rpm. I was driving yesterday highway speeds and the upstream were jumping downstreams were steady. I hacent changed the downstream sensor on b2. Now today...ran a smoke test for thr evapcode 0455 large leak...folloeing the smoke we foubd a cloud coming from the fuel pump.

Could you see where on the pump with a mirror up there?

 

[BlueCollarTahoe]

Could you see where on the pump with a mirror up there?