Just when I think all is fine...

My '88 240 starts up fine, idles wonderfully, and usually will take off from initial start-up just fine, but after it warms up, will start to hesitate (sometimes jerking and bucking) while applying the accelerator pedal. If I try to rev it up at that state, it will bog down and seem to surge, sometimes with a backfire. The more I push on the gas pedal, the slower the engine gets. The only way it will clear up is to shut the engine off, then start it back up. If I rev the engine then, and it revs without bogging down, then I'm good to get back on the road...at least until it starts losing power again. And when it does start up and rev fine, white smoke temporarily comes from the tailpipe when engine resumes idle. This morning alone I stopped 8 times on the way to work to get it to run right.

Both fuel pumps have been replaced within the last year. Fuel pump relay also (is it supposed to be warm-to-hot to the touch?). The fuel filter is also less than six months old (got another one anyway), and I took the intake and throttle body off and cleaned it out really good just a few months ago, and soaked the injectors in carb cleaner before putting it all back together. I also replaced the fire trap/oil box with a new one.

It also seems to run just fine in cold weather. We just had a warm front move through and just as I predicted to my girlfriend, my Volvo started running like crap again.

Any ideas?

 

Ok, never mind. Got a whole new issue now.
After changing the oil and replacing the gasket and o-rings to the water pump, due to a leak, I started the car to check for oil pressure and to properly fill up the coolant levels. It suddenly died and would not start back up. It smells like there is fuel, and the fuel pumps run with the ignition on, so I don't think that not having fuel is the problem. I checked for spark at the plug and there isn't any. I checked for spark at the distributor from the coil wire, and there is none.

1) The ignition control unit has power at terminal 10 and ground at terminal 2.
2) The coil is receiving power at terminal 15.
3) The resistance between terminal 1 and 15 on coil is 1.4 ohms and between terminal 1 and tower is 11300.
4) I tested the ignition control unit switching function and it produced a strong spark at spark plug.
5) The test for power to Hall sender indicated there was power to it.

Is there good indication that the Hall sender is faulty? I've looked online and found the sender (they call it Impulse Sensor) on swedishautoparts.com but without metal trigger wheel.
I wonder if this has been the source of my erratic power loss all along? The one on my distributor has a broken housing.

 

Ok, so I gave into my misgivings about my own diagnosis and took it to a shop where he not-so-promptly gave me his own diagnosis...which was exactly what I thought. The hall sensor was shot. He replaced the distributor (Bosch) and the coil. $586 later, including labor, I had my car back.

But...I still have the problem of losing power under a load, say up a hill, or anytime I push the accelerator beyond what I consider to be half-way.

 

loosing power or Engine lacks power

Areas to look at/check

1) plugs...how old? tune up done?
2) O2 sensor...if old or crusty inside will give you problems
3) check for battery/alternator voltage just to rule this out and keep narrowing it down for you and us as we don't have the car in front of us.

4) Trans fluid color & amount....dark...cherry red?

cleaning the MAF sensor will help tremendously.....MAF cleaner and let it dry before re connecting.
Haynes diagnosis for engine lacks power:
11) emission control system not functioning properly(cat converter clogged & old o2 sensor)
12) Low or uneven cylinder compression pressures....(worn rings or time for a head gasket job) you say you are looking at white smoke?...head gasket needed if you continue to see this

 

1) plugs...how old? tune up done?

Right before I had to have the Hall sender replaced I changed everything from plugs to the rotor button.

2) O2 sensor...if old or crusty inside will give you problems

I can take it out and check?

3) check for battery/alternator voltage just to rule this out and keep narrowing it down for you and us as we don't have the car in front of us.

Alt. is giving 13+/- while running.

4) Trans fluid color & amount....dark...cherry red?

5-speed, manual. One other thing, I don't even have to be driving for this to happen. I can be sitting in the driveway and rev the engine beyond half-throttle and it "bogs" down.

11) emission control system not functioning properly(cat converter clogged & old o2 sensor)

You know, I'd thought clogged catalytic converter too, so I took it off to see. Someone had previously cleaned it out. It is a hollow chamber.

12) Low or uneven cylinder compression pressures....(worn rings or time for a head gasket job) you say you are looking at white smoke?...head gasket needed if you continue to see this

I'll break out the compression tester and see what I get. That didn't even cross my mind.

Thanks for the tips!

 

great...
1) tune up.....check
2) cat....check
3) battery.....check
4) compression testing....pending....
O2 sensor if all white and crusty will not help with your idle or fuel/air mixture...I believe. Mine had this white baked on powder blocking the little slots were the air can be analyzed by the sensor...changed it and idled a lot nicer...no fuel smell out of exhaust..you can unscrew and screw
do unscrew it after running the car as these things are almost melted in the exhaust.

5) TRANS FLUID....YOU DO NEED TRANS FLUID ON A MANUAL...ABOUT 1 QUART OF ATF...easy job to do...just jack up from driver side....two screw plugs...top & bottom....TOP TO fill and bottom to empty....
Get yourself a fluid pump or the hard way like I did....just screwed on a spray bottle top to the ATF quart and squirted the entire bottle(top squared screw plug) and two hours later I was done....Harbor freight fluid pump will save your fingers.