Weak spark

Haven't checked current, but all three coil signals show 14V. The coil is an aftermarket (Driveworks from Advance Auto). I may take it back and see if they'll replace it. Plug wires are 5 year-old Autolites, so I'll replace them. Plugs are only a year old ( 8K mi) and look good.

Thanks for your response.

Haven't found much yet. I put the old coil back on and returned the one I bought to Advance. It idles a bit better, but still misfires at load. So far no return of the P0135 code. Still get a bright pulse on the #2/#6 primary terminal, but voltage is still 14V at all primary terminals and spark is weak at the secondaries. When I get time to work on it some more, I'll replace the plug wires and coil again. I'm beginning to suspect PCM problems. I don't think this car has a CCRM, but there is a cluster of three relays (with a fourth empty slot) in a case next to the battery, which could perform the same functions, so I may try moving those around.

Any more ideas?

Ken,

Won't have time to get the plug wires on for a few days (death in family). Not clear why old plug wires would cause a brighter test lamp or a weaker spark to a grounded test lead, but they're due for replacement anyhow. Will let you know what happens.

Steve W,

I'll test the original coil as you suggested and then get a new one to see what kind of spark it produces Like I said, it will be a few days.

Okay. Got back to it yesterday with a new set of plug wires. Immediately idled better, even with the original, cracked coil pack. Still got a misfire under load, but no codes. Replaced the coil pack with a higher-grade aftermarket. Seems to run well, though haven't had the chance to drive it a lot.

It has occurred to me that a weak plug wire might cause the computer to compensate with a stronger primary signal; hence the brighter test light, which had me ready to blame the PCM. Thanks for talking me out of it. It just never entered my mind that there could be two related and simultaneous problems.

Maybe I'll next figure out what's up with that occasional complete power loss on this car during hot weather. Everything dies (usually idling at a red light) and the outside temp on the panel reverts to compass direction, meaning, I guess, that the PCM has lost power. Always starts right up again and goes on. Probably AC and cooling fans triggering a systemic power loss of some sort.

Thank you both for your help and words of sympathy. Is a contribution in order?

I don't think it's so much the heat as the fact that both the AC and cooling fans fire up at the same time. You may be right about the old cracked coil being the culprit. We'll see when the summer heat hits. Not a priority right now. It's an annoying problem, but not one that I'm going to waste a lot of time on.

Thanks to you guys for your help. Anything I can do for you?