hi,

i had a persistent damp weather bad idle issue in my rex/regina 94 940. codes were thrown which i addressed but the damp/rainy day idle issue continued, over several years. i had excellent responses in the past from fellow bb's, but the advice didn't work for me on this issue.

i replaced with new/used items: o2 sensor, coil pack, knock sensor, rewired knock sensor with sheathed wiring, replaced spark plug wires, distributor and rotor, cps, vacuum hoses. but still persisted. (i kept most of the replaced stuff, and kept the old wiring intact for the knock sensor rewiring, just in case).

my 94 940 distributor is located by the alternator, engaged with the immediate cam shaft, not in the rear of the head (93 and earlier 940s).

symptoms were the car would start, but after a minute or two from a dead stop to driving, the car would die, and once started, would idle rough. i would need to let it warm up for about 5 minutes or longer before it would smooth out.

i even tried looking at the distr cap for moisture.

after several years of this problem, i read about using wire dry by crc. i cleaned the little residue on my cap and rotor and sprayed the rotor and cap, along with the coil pack and spark plug wires.

i don't have a bad idle issue any more, after a number of days of rainy/wet/damp days, even after letting the car sit for a few days.

assessment:
certainly the damp weather caused the idle issue. on dry/sunny/warm/hot days, i never had a problem.

i don't think spraying the s/p wires and coil pack improved anything.

these symptoms for others may not be resolved by this crc spray, it worked for me.

i didn't try wd40 or other sprays on the distributor because i thought it leaves an oily residue which i didn't want on my cap or rotor. the crc spray evaporates but apparently leaves enough of a waterproof film to prevent moisture buildup, but not enough to interfere with the cap and rotor function.

it's been over a month now with a number of wet, damp, snowy days, and i read from that post that the person plans on spraying his cap and rotor in about 6 months as a pm measure. i will wait until i have this issue again just to see how long this crc spray lasts.

i plan on doing the same to my 2 240s as a preventive measure.

again, rwd volvos come through again with just a simple fix. volvos were built smarter than the people driving them, mostly, and i include myself in that description.

hope this will help others with similar symptoms.

byron golden
86 245
92 245
94 940

Do you have all the wire clips and looms that you should have? one or more might be missing, I have seen several 740s with missing clips, they get brittle after some time. A look at the parts diagram can let you know what might be missing. a couple of extra looms never hurts.

Did your wire kit include a coil wire? I found that the coil wire on one of our 740s had a crack where it was clipped to the firewall.

If you have a wet, rough idle, try looking under the hood at night.

Lastly, pull the plugs after a minute of rough idle, one or more might be cold or wet.

hi james,

all good points and thanks for your reply. i didn't think about looking at the wiring looms, but i did replace a number of the female bullet connectors with the decomposing bullet insulation.

and i didn't pull the spark plugs to look for moisture, but that was a thought i had. i guessed that something electrical was damp.

about your other points, all yes. checking for sparks at night, s/p wires with the coil wire.

it's been about 2 months now since i applied the wiredry, and we've had a lot of damp and rainy days, including yesterday here near houston.

so far so good.

byron

MAYBE AIR LEAKS SOMEWHERE LIKE THE THROTTLE SHAFT??

i should say that the a/c bellows leaks are closed leaks meaning when i accelerate, the vent goes to the floor. it is not an outside leak affecting the intake vacuum.

hi peter,
i checked for air leaks, split vacuum hoses in the engine bay some time before applying the wire dry spray; no leaks heard inside the car.

i have some leaks in my a/c vent bellows, but the check valve stops losing vacuum going to the engine intake.

other than that, i never heard of a throttle shaft for or in a 940. can you elaborate?

good points.

byron

A throttle shaft leak is typical in high mileage cars. Whether it is related to your symptoms or not is difficult to ascertain without a smoke test along with some corrective action. It is caused by wear at the throttle body where the throttle plate's shaft is held.
--
Art Benstein near Baltimore


"Keep in mind that random processes can fluctuate in such a way as to mimic a signal when no signal exists." --Ransom Stephens

hi art,
got it, thanks. never heard of a leak occurring through the shaft, but yes, could occur.

byron