[jcp123]

Originally Posted by California98Civic

An interesting thing then is that short term trims will read very lean, sometimes way over -10% and often under high steady load (climbing a 1.5 mile steep hill on my commute) I have seen short term trims of -26%. My long term trim might be deceptive because P&G has always produced modestly positive longterm trim, such as +0.78 or +1.56. So what happens on the freeway now that I have taller tires and am steady cruising at light throttle is the longterm trim gradually moves into negative territory. If I had a longer ride it might get -10% or higher eventually. That make sense? If true, my car has been possibly feeding unburned gas into the CAT for a VERY long time.

I resistance tested my ignition wires just now on a lunch break: the #4 with the unburned gas on the plug has oddly low resistance in the wire. I got a bunch of reading near zero on the 20k scale. See attached notes:



Number 4 wire is faulty, I gotta think.

[EDIT: AND I TOTALLY WILL CHECK THE OBD2 DATA OUTPUT FOR THE DOWNSTREAM SENSOR. THX.]

Hmm ok, strange the long terms aren't adjusting (they usually follow short terms fairly quickly) but with short term that far out, then yes I would definitely want to check out fuel and spark. If you have an INCANDESCENT test light (say NO to LED for this test), ground the claw and hold the other side out from the boot while cranking or running. It's a quick and dirty test but you want probably at least a 1/2" of spark (preferably 3/4") reaching out to your test light from the bottom of wherever the conductor is buried in that boot, and with the resistance of the incandescent bulb you both put extra resistance in the circuit and avoid damage to the ignition and/or any computer drivers.

Low resistance is strange, but remember that you're checking that wire unloaded, and unloaded circuits are strange. Put said incandescent test light in-line with your multimeter and see what the resistance does, compare to the other wires.