3 coils, secondary test reads 13.3 on all 3 coils.Both O2 sensors changed 6 months ago, mileage is now 112000mi. Aoto zone diagnostic said misfire on plugs 2,4,6 ...replacedplug wires and switched 3rd coil with middle coil...test readout changed to random misfire. What do I test next and how to do it? getting worse.,,engine ok till heats up and now often idles rough
intermittent stuttering,power loss uphill, primary coil test reads1.2ohms on all on 1997 Toyota Avalon
by mexicaned in Denver, CO on August 05, 2013
2 answers 1 comment
ANSWER by lightsaber on August 05, 2013
Primary resistance from Haynes manual should be cold .70-9.4 ohms hot 0.85 - 1.10 ohms Secondary resistance Aisan coils cold 10.8-14.9k-ohms hot 13.1-17.5 k-ohms Diamond coils cold 6.8 to 11.7 k-ohms hot 8.6-13.7 h-ohms A new toyota coil I tested had 1.0 ohms for the primary, and 13.3 k-ohms for the secondary. The best way to check for a bad one is to purchase a new coil and swap it into the three positions and check for improvment in running. Coils will fail anytime after 90,000 miles. Amazon.com has ok prices on coils. If a coil was bad, you would have one front(2,4,6) and one rear (1,3,5)cyl misfire as it is a waste spark system, but you do not appear to have that symptom. You should be looking for a bank 2 (radiator side) specific issue which could be the rubber boots on the bottom of the coils, but I would not rule out plugged up catalytic converter, fuel system issue, coils, or oxygen sensor. Who can say without testing? Use a small dab of dielectric grease on spark plug terminal before installing plug boots, and check wiring harness. Did you install the plug wires correctly? Has the timing belt been replaced?
COMMENT by mexicaned on August 06, 2013
many thanks for your advice, I did replace the plug wires and boots and 6 months aga both O2 sensors.
ANSWER by pushrod on August 05, 2013
IF, and only IF, IT HAS AN OBVIOUS MISFIRE AT IDLE, then test the plug wires and coils the old fashion way. Pull one wire off, if miss gets worse put that one back on and go to the next one and do the same thing. If none of the wires are bad, check coils the same way. The coils seem to be within specs. but it still could be one or more coils defective. Most likely only one. Possible plug boot on coil leaking spark! OHM test plug wires also.