'99 Corolla "Waste Spark" Ignition Coils - Cyl 2, Cyl 3, Random Cyl Mis-fire Detected

Joined
Sep 30, 2017
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Location
Vancouver, BC Canada
Per the detailed title, I both have the above 3 codes being registered and, somewhat strangely to my way of thinking, I am experiencing a low rpm miss that comes-in just beyond cold start. ... Meaning, all is good until coolant temp is closer to normal operating temp. Also, this misfire appears to be throttle position dependent. I can experience same, then if I back-off the throttle a 'wee bit, it can disappear. Going deep into the throttle causes backfires. Generally the miss only occurs at low- to moderate RPM's. Higher RPM's - NP.

It clearly is not a clogged fuel filter (fuel pump inlet sock) as higher RPM's are NP.

I am 'gonna switch positions of the coils, as cyls 2 & 3 are fed by one; cyls 1 & 4 by the other. If the prb migrates that likely is an indicator of a prb coil.

Plugs are good; spark plug leads are new.

Any idea re the prb, other than a bum coil?

Is it possible that the richer mixture on startup CAN be ignited with a weak spark, but normal temp "leanish" mixtures are a prb? But why only at lower rpm's?

Thank you to anyone who could advance a thought on this.

I attach a screenprint of my older Android phone with the Torque app. The O² sensor voltage flips with, I believe, adequate frequency...
 

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Joined
Mar 20, 2008
Messages
14,136
Location
USA
If it's between those two only, and the same coil fires both of them, and the other cylinders are fine, it's probably the coil. Swap 'em and see what happens :)
 
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