Hey, all. Having a running issue with our '92 Volvo 240 and I'm newly moved without a good mechanic, so hoping some finer minds here can help me diagnose the problem. Took it to a recommended place here in Richmond, VA, but, despite what they claim, they don't seem to know 240s very well and couldn't figure it out.

Basically, after most (but not all) heavy rains or snows, if the car sits for a while, it has trouble starting and in a couple cases, won't start at all until it's dried out. To get it to start in these situations, I have to floor the gas and then run it high for a few seconds to keep it going. Then it'll drive decently, but near-stall at stop signs. Running it high on a highway for a couple minutes cures it of all that ails it.

Distributor cap seems good and on well to me, for what it's worth.

Some additional clues:
1. Car runs fine when it's begun raining, it needs to sit for a while seemingly in the dampness to develop the problem
2. Running the car high after it does start cures it, as said, even if it rains more and sits for the short term (it's fine for the rest of the day, usually)
3. Engine always turns—no problem there—just doesn't always start in these conditions
4. When I do floor it to get it to start, it seems to generate some noticeably whiter exhaust
5. It also runs a little unevenly for a while after a difficult start until it gets the water or dampness out of its system

Thanks in advance, y'all.

 

You probably have moisture induced arcing in the distributor/rotor/wires/coil - arcing to the wrong place. If you don't know what arcing looks like in a cap - you might be missing it.

You could try using a spray bottle of water - and spray the high voltage components with the engine running in a darkened environment to see if any arcing is visible -

 

white exhast, feels moist ?
frothy white residue on underside of oil fill cap ?
noticing the sweet smell of antifreeze
temp guage high or lower than normal
water bottle emptying but no apparrent leak
white froth on dipstick ?
-symptoms of blown head gasket.

- it might also contaminate the O2 sensor - possibly.

 

it would be worth it to remove the distributor cap and inspect the inside contacts as well as the condition of the rotor... it's the only way to know for sure.

mine would stall at lights but still running - then i found this!

https://volvoforums.com/g/picture/7897572

 

Agree on the mist/dark garage diagnostic trick. Otherwise, if you don't know when the cap/rotor/wires were last replace, just do a "stage 0" tune up: Plugs, wires, cap, rotor. Check Volvo sites like IPD or FCP for a kit - should run you about $90 for parts.

Note most wires have a date code on them - if they are over 5 years just replace them. I've also found corrosion inside the rubber boots on the wires going to the distributor/coil wire.