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240 dl backfiring, running badly[ALL/1988] posted by mike leech on
Thursday, 22 January 1998, at 7:32 p.m.
An 86' 240DL I am working on has been driving me crazy. The car has a new
computer, distributor,cap, rotor, plugs, mass airflow sensor in it. It
continues to backfire, miss and hesitate, cold and hot. I put it on a
diagnostic machine when at the end of my wits, and got all kinds of great
information that I cannot relate to anything that isn't new. The exhaust
reeks of fuel at all times, and although it only misses slightly at idle, when the throttle is accelerated it begins to shudder, and attempt to stall. I
vacuum to the fuel by pass under the intake, no change. i disconnected the massairflow sensor, the car shut off. I can hear the fuel pump, so i believe
that it is OK, and i cleaned the flame suppressor, no change. I have checked every sensor, vacuum and electrical that i can find, and none of them show any change at all, however the cylinder effiency on the computer went back into the green with the new computer installed, and the old computer was burned on
one corner. I have tried 3 computers, all the same as the factory one, and they all have the same effect. The exhaust HC and Co2 are still out of range, and so are many of the specs the computer spit out. I, and several other people are stumped. If you would like to see the diagnostic information from the machine, e-mail me, and i will send it to you. Any help would be greatly appreciated.
Thanks, Mike Leech Sofast442@aol.com
Re: 240 dl backfiring, running badly[ALL/1988] posted by `irv klein on
Thursday, 22 January 1998, at 11:56 p.m.
This seems to be a recurring problem on the thread. These are relatively simple cars to diagnose and I have always found that when I cant come up with a simple answer it could be the dreaded "harnessitis" discussed in previous posts. Before replacing parts wholesale I would check the connection to the distributer as well as the wiring going from the distributer to the ignition module. Rip off the sheath encasing the wires, check them out individually. Particularly take note where the wires go under the crankcase pulley. Many times the combination of dripping oil, water, salt from wintry roads tends to break the protective sheath at this low point. Those elements combined with the general decomposition of the electrical insulation and you can get intermittent shorts in the wires leading to distributer. Very hard to diagnose but I would carefully chck each wire and insulate with good electrical tape "individually" - dont bundle them. Volvo's solution to the problem is to replace the Hall switch in the distributer as well as the ignition module and the complete harness. I guess that would work if ya have a couple grand ya dont need.
Re: 240 dl backfiring, running badly[ALL/1988] posted by Johan J. on
Friday, 23 January 1998, at 7:16 a.m.
It appears most of the electrical stuff is o.k.
I would concentrate on the fuel intake system. Maybe a faulty pump, or
relay. Check fuel pressure. It could also be water in the fuel.
I would also check compression on each cylinder. You could have a blown
head gasket.
Good luck ! You'll need it !