AFR dipping rich at startup!

[Whitemanfro]

S13 setup:

Stock redtop with stock 62 ECU
Stainless steel downpipe
Innovate LM-1 wideband
using skinny M12 o2 sensor

Symptoms:

When the ignition is applied and wideband warms up
Air/fuel ratio starts out just right, then slowly creeps down to ~12.0, hesitates there for a minute, creeps back up to over 15.5, then finally stabilizes around 15.3 (at idle)
this happens when o2 sensor is plugged in, and worse when it is not

Possible causes?

I tried both my skinny and fat sensors, no difference
Does my exhaust need to be grounded better?
-I am getting resistance on my multimeter from the downpipe to the chassis


I am lost on this one!

Thank you

[di-devol]

You need to stick with the skinny o2 for the redtop sr.
I dunno about the resistance you're getting.

If it's when the engine is cold, that's the startup enrichment table, supposed to be rich when first started.

If this is when the engine is warm, could be something else.

[Whitemanfro]

Thanks for the reply

Im running the skinny o2

Only happens when engine is warm, brand new coolant temp sensor also

[steve shadows]

Have you checked for injector leaks? Have you checked your fuel pressure? Have you checked the condition of you IACV? Is the IACV connected? What about full vacuum leak testing? What sort of condition is your engine harness in? All of these things add up!

[Croustibat]

If you have a BOV, block / remove it, they nearly all leak when throttle is closed (when the vacuum is maximum)

[Whitemanfro]

Tomei FPR is installed, running OEM fuel pressure
replaced all injector orings and pintle caps, as well as tested all injectors 2 months ago

IACV has been cleaned, although Ive never taken it out.
I was able to adjust idle to 800 with ease using it though.

I have a new O2 3-pin connector coming in the mail, I will be rewiring the whole shabang in the coming days. I hope this combined with a good ground will smooth out my krinkles