78 Volvo 242GT Gagging/Staggers Problem

volvo
240

#1

I’m motoring along at speed & suddenly the car jerks once or several times with such violence that it pops out of gear leaving the engine racing. Everyone in the car is jerked hard back and forth; if this model had a cup holder the coffee would blast straight up. It feels like the windshield is going to flop out and the motor mounts throw up their hands and the whole shebang just drop onto the pavement. Then it carries on as if nothing happened. And (a figurative) POW JERK JERK JERK…repeat
I call it “stagger” or “gagging”; it happens more in hot weather, more when the engine is hauling up a hill. Not so much in cold weather.
Based on that I’m guessing it’s not electrical but fuel line related. (This car has a functioning vacuum pump which sings in hot weather.)
So, does this model have 2 (TWO) fuel pumps? One under the rear seat and one ??? But why would it happen so much more often and with such violence in hotter weather? And how do I or Mr Hansen fix it?
Help! Any ideas?
I’ve driven this car all over the West for 30 years. This problem started only a couple of years ago.


#2

Actually, a violent bucking is more likely electrical than fuel.

It could be something like a cracked ignition coil, which can cause intermittent loss of spark when it gets hot. Which may be why you notice this problem in hot weather and when the engine is hottest, ie working hard uphill.

I would first check all major electrical connections (battery cables and grounds). If no obvious problems there, I’d try replacing the coil. And if that doesn’t fix it, check other ignition components (distributor, etc).