running lean

SON240sx Automotive
1

hey guys what’s up

I finished my s14 blacktop -> s13 swap about a month ago and wasn’t very impressed - something wasn’t right.

I finally got an AFR gauge and it’s telling me I’m running pretty damn lean (~0.05V most of the time). knowing those gauges are crap for the most part I went for a few boots with my voltmeter hooked up and I was still getting the same voltage.

I pulled the plugs out to take a look and they’re pretty much spotless. the porcelain has a bit of carbon on it but it’s still fairly clean. I installed a walbro 255 and have a 300zx fuel filter. other than those mods the fuel system is stock.

the gauge/voltmeter is running lean during idle/ regular driving / WOT. I’m venting to atmosphere and once in a while when that happens it’ll spike rich for a second (expected) but it doesn’t happen all the time.

any clues what’s the heck is going on? clogged injectors? lose wires / bad ground on the walbro?

2

Is the AFR gauge hooked to a wideband O2 sensor, or just your stock one?

If it is just the stock one, chances are its got tons of KM on it, and isn’t
working as well as it should. The first step there would be to replace your
O2 sensor (only about $60).

You can’t really get a good reading from a narrowband O2, you need a
wideband to draw any conclusions from it. I had my AutoMeter A/F gauge
hooked up to my stock O2 sensor, and it would always read lean, although
the car was actually running slightly rich of stoich.

If you can take the car to a dyno that has a wideband, and just do a run.
Then you can see if its actually rich/lean, and by how much. As a bonus
you’ll also get a power readout, and see if the motor is running as well
as it should be.

My nose is better than a narrowband O2 when it comes to telling your A/F

:stuck_out_tongue:

3

yeah it’s stock O2 sensor that’s another problem heh,

there’s no black smoke during vent / WOT (currently have no cat either) which leads me to think it’s actually running a bit lean.

this is the first time I’ve had this happen so I’m not really sure what lean exhaust gas smells/looks like :frowning:

btw, you goto laurier bro?

4

If its lean the motor will run alot hotter, and the exhaust won’t smell as
much like gas as if you were running rich.

Its very rare that people run lean when doing SR swaps. Running rich is
alot more common. Just because you don’t get black smoke doesn’t mean
its lean. Do stock cars have black smoke comming out of them? No. Do
stock cars run lean? No.

If you don’t hear any knocking you’re fine. If you’re really concerned then
hook up a wideband.

And yeah, I go to WLU :smiley: