I have a 1987 240DL wagon. I can do 80+ mph on the highway for about 100 miles or so when suddenly the car will have a very hard time accelerating (usually uphill). When I press down on the gas pedal, the engine will stall and backfire. It will only stop stalling when I let off the gas. So, the car travels slower and slower until everyone on the road is passing by me. At that point, I usually pull over on the side of the highway and turn off the car. After waiting a few minutes, the car accelerates again, but slowly. If I wait longer, the car will drive like normal for half an hour or so. Then the problem occurs out of the blue again. This is extremely annoying. My four hour trip home yesterday took almost 6 hours with all of the stopping and waiting.

Has anyone had this problem before? What should I look for? I recently replaced both fuel pumps and had the timing adjusted.

I appreciate any and all insight into this weird situation. Thanks!

Have you replaced the fuel filter ?

sounds more like spark problem

these happen [eg at coil, spark plug leads or dist cap] when heated up

I would spend $20 for starters on a new set of leads

how hot is it getting? Does it ping? Why adjust the timing-it requires almost no adjustment once set-I'd recheck the setting VERY carefully. if pointless ignition, then I'd go straight to ign timing as a source of trouble, as it prob didn't need touching at all. Follow manual PRECIESELY to get it right. NB. even this early motor may have had the self-adjusting ignition timing and anti-knock sensor. it needs some clear thinking to set it properly. Amateurs would get it wrong. If timing ok, then check that have you enough correct oil, correct tappet clearances, correct and sufficient coolant? errors here will overheat your engine as described. loose belts, bad radiator, leaking or blocked cooling system/airflows/low grade fuel/blown head gasket/bad thermostat..........NB correct coolant concentration and frequent changes of same critical & ESSENTIAL to motor survival. Remove oil filler cap and examine in rocker chamber for oil sludges sticking to the metal parts and the head. If the gluggy porridge-like filth is present, your motor has probably been terminally overheated, very few motors long survive the occasions where the temps produce such oil sludges.

BEWARE of plastic bags-they wreck radiators etc. A motor doesn't have to seize to be ruined, excess heat expands the piston/rings against the cylinders and makes them scrub-wearing them down . You stop the motor and it cools down, the piston shrinks-smaller than it was before because of the wear, and the engine oil consumption skyrockets and the compression falls. you lose power and waste fuel and oil. The excess heat can draw out the hardness from the bores, and render the whole block useless. I've ignored the great likelyhood of warpage of heads and blocks, and the great cost of repairing them properly.

Thanks to all who read and replied.

The fuel filter was replaced when the fuel pumps were replaced. I replaced the spark plugs, wires, dist. cap, but not the rotor because Advanced Auto had the wrong one. All the fluids check out fine. Correct levels and all.

The engine doesn't overheat. The temperature gauge remains constantly just under the half-way point. The problem with the lack of power only seems to occur on long distance highway driving. Around town, the 240 is sluggish but it doesn't backfire or surge like it does after an hour or so of 70 mph highway speeds.

It seems odd that the car returns to normal when I pull over to let it rest. The surging disappears and whenever I floor the gas pedal, it drops to the next lowest gear without problems. When it does surge and backfire, it seems as though it isn't getting enough fuel or spark. I somehow suspect some ignition component. Perhaps the ignition coil? Like I said previously, nothing is suspect until the Volvo's made it 70-100 miles away from home. Then, I take 15 minute breaks every half hour.

I love this Volvo wagon. I want it to be dependable on long trips. Any more ideas or suggestions? I tried to have a local shop look at it but the problems couldn't be replicated. They didn't want to send someone out for an hour just to drive the thing down the highway.

Thanks, again, for the ideas

What's the weather where you are? Have you tried it on a cold night? I still think it's heat related, or perhaps something in the fuel system which builds up. Its a pity you can't easily heat things to see what happens. Does it start sooner if the tank is low? That would indicate something to do with the fuel temperature, as it gradually warms up whilst you drive. I would fit a fuel pressure gauge and see if the pressure drops abt the time you have troubles. Your pressure regulator may be shot, & that model isn't expensive, BUT check the presure first! I believe 36psi is correct, post again when you have a figure, as it's got to be close to that to work properly.

I read a post somewhere with similar symptoms and it was small cracks in the solder inside the fuel pump relay

I would check the cat converter and O2 sensor.

It is blazing hot here in southeast coastal GA- 96-100F. On a cool night, going down the highway, it does indeed take longer for the car to exhibit the surging/backfiring problem. I do notice that if the wagon sits overnight or for an extended period of time, it takes much longer for the surging to happen.

Next week on Monday, I will be using the Volvo for meals on wheels- 25 houses to visit, 70 miles stop and go, and heat heat heat. So, I will get to see whether or not the problem only occurs at extended periods of higher speeds. I am trying to replicate the problem, but I have no need to drive 100 miles right now.

As suggested, i will:

-Check my fuel pressure when the surging problems come up again.
-look into the fuel pump's relay- the shop didn't replace this item when it replaced the fuel pumps and filter
-is there a check for the fuel pressure regulator? I purchased one on eBay only to have it not fit (it seems to fit the 88-on 240s but the seller led me to believe it would fit my 87 as well)

The problems persist whether or not the fuel tank is full or empty.

I will, of course, keep everyone updated on the developments. It has been driving fine around town. It's a bit slow on acceleration but I haven't other Volvo 240s to base this on.

Here's another thought- my exhaust pipe was severed until this morning when I had the exhaust shop weld a new pipe in it's place. Not only is the Volvo much more quiet, it seems to have a little bit more power. Could the lack of back pressure have any direct/indirect effect upon the engine's performance?

Again, I really appreciate the thoughts and replies.

Is your Catalytic converter blocked? Rich running destroys them-they melt and often block-exhaust shop should have noticed it. Lean running might also overheat them-(from leaky exhaust)-they are, apparently, sensitive to exhaust temp. fit the regulator, it's only 3 bolts on a cold motor-ign/battery off-there will be some fuel spray when it's undone, so expect fire risk. Give it time to dry and then ign on w/o startup circulate the air out, or expect it to crank a lot and run badly until it's clear. Do check the O rings on the fuel ports, make sure that they are clean, good fits and undamaged b4 fitting. Q? Does engine suddenly lose power, or gradually weaken? My 88 wagon is quite a rice-pudding machine, only the turbo's had any real performance, and <mounts tall equine> stop-start driving will murder your fuel 'economy'-partic if she's automatic. I still suspect your fuel temp has a lot to do with it, but as yet I'm unable to say why. Regulators are fairly simple devices, and can slowly degrade and become very heat sensitive. At our vehicles ages/milages, expect quite a few parts to fail, especially electronic and mechanical bits. Major Brake & clutch hydraulic failure occurs at least every 14-15yrs. Expect it!

you did replace BOTH fuel filters didn't you? one in the tank with the motor,the other near the Left rear wheel(?) front of. if it seems heavy, that's probably whats wrong, its blocking up, leaning out your motor. A problem I had abt 30 yrs ago with an old Hi-Ace, now sounds very similar to what you have. I'd drive abt 30min, and suddenly drop back to 35mph max. I was carrying the new filter from months earlier, because I hadn't found it yet to replace it. the pump replacing mechanic-is he familiar with Volvos, or is he just cheap? He should have at least advised you to replace both filters-if not, I'd be reluctant to go back. I'd then doubt he knows his job, & I'd be much averse to training him at my expense on my car. Any good mechanic should be able to work out these cars, but the usual garden variety aren't good enough. They tend to be specialist vehicles, which always cost more to service, thus DIY is to be encouraged.