Awhile ago, my car was misfiring, and I thought that I had cured
it by putting dielectric grease on the plug wires? Well, it's
baaaack. After letting my car sit in the wet snow for a day, I
drove it today, and it was missing at around 2,500rpm under load.
Also, the idle seemed a little shakey. Playing with the plug wires
seemed to cure the miss, but, oddly enough, squirting water on
the ignition system when the car was running didn't cause it
to stall out. The wires were replaced in Dec. 2002 by the previous
owner, and they are the kind with the huge metal ends. Could
the wires or plugs still be at fault? The plugs are around
12,000mi. old, but I cleaned them recently, and they looked all ok.
.
TIA -b.

A misfire under load is not always connected to the ignition system... it could also be a vaccum leak.

To start, I would check all the rubber hoses around the intake, throttle body, and bellows.

Then, I would start checking the gaskets -the spray method works here too.

Finially, I might suspect the coolant temperature sensor, not the temp. guage one, & the knock sensor.

The misfire under load in my car, which took eons to track down, was related to the flapper door inside the airbox... which I subsequently removed... problem solved.

Some thoughts, Jon

I remember this from awhile ago, but not details.
How is the cap and rotor?
How about the coil?
If you sprayed the wires and no change , it could be the cap or coil (cracks in them).
Make sure the plug gap is correct (not a solution, but it helps)
--
744-16v-4+OD 185kmi., 745-16v-4+OD 359kmi., 242Turbo-4+OD 170kmi?, 245DLT automatic 287kmi.

I actually soaked everything in the ignition system - wires,
plugs, coil, distributor - with no problems. The cap looks fine,
and so does the coil. Maybe the problem is under one of the plug
shields, and current is shorting to the metal shield and thence
to the block or exhaust manifold? The plug gaps are dead-on,
reset a week ago.

-b.

If it isn't leaky insulation, it could be broken conductors. After 5 years with eight Volvos I haven't yet had a problem with ignition wires so I can't tell you what they should measure. Used to be a thumb rule of roughly 5K ohms per foot on carbon radio suppression wires. Don't know which engine or year you have, but I did once have a B23F with a burned out resistor in the rotor.
--
Art Benstein near Baltimore

I just replaced a rotor on an 83 with a B23F because the engine had no power under load. I has using an ohm meter to check plug wires (all read around 5,000 ohms) and decided to check the rotor button and cap while I was at it. I cannot remember what the rotor read put it was way up there. The new one read 1 ohm and the power was back. jp