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Will spraying WD-40 on my distributor help?

Short story is my 1988 Civic Wagovan (4WD 5spd, 140K) suddenly started running terribly today when I went out to start it up.

Longer version is that I had the ignitor in the distibutor replaced last week, and it was starting and running fine since I picked it up from the mechanic. Today when I went to start the car though, it is suddenly running extremely roughly, coughing and dying, and the exhaust is shaking and coughing/spitting. The gas pedal is basically unresponsive. My first guess is that is may have something to do with the recent work that was done on the distributor. I called the Honda place that fixed it, and the mechanic recommened that I spray WD-40 on the outside of the distributor to try to get rid of any moisture that may have been interfering. I’m hesitant to do this but will certainly give it a shot if it sounds like it might help.

Does anyone have any experience with this and care to offer any thoughts on the matter?



The WD-40 trick will help diagnose a distributor cap or ignition wires that malfunction when they get damp, indicating the need for replacement. IS the problem you’re having related to damp weather or a trip to the car wash?

It is useful for testing, but if it works, it means you have a problem, it will not fix the problem, you would still need to address the problem, like old plug wires.

It has been raining today, though not hard and not for very long. This would basically be a temporary solution so that I could get the car back to my mechanic. Thanks,


It may shock some here, but water does not conduct electricity. Utilities use distilled water to clean insulators with 500,000 volts on them. Dirty water does conduct and that WD-40 will start collecting dirt. If it works, it won’t be a long term solution.

??? HUH???

OH is correct. It’s the stuff dissolved in water that conducts electricity, not the water itself.

But when was the last time distilled water fell from the sky as precipitation?

This may help:

This can be an issue with equipment like coffee brewers that use continuity-sensing level probes-- if people use distilled water with them, the probe doesn’t ground to the body when the water fills up and you have a mess!

i will have to make sure to drive through distilled water puddles only from now on.

that is interesting, i must have slept through chemistry class that day.

but where in the real world do we find distilled water as a criteria for determining whether water is shorting out a distributor?

Water conducts electricity - distilled or otherwise. It’s the Ions as the article explains - don’t you remember your grade school science class?

They use distilled water to clean high voltage insulaters because it doesn’t leave anything behind after it evaporates.

By the way the “WD” in WD-40 is an acryonym for “Water Displacement”. WD-40 was developed as a water displacement/rusr preventative treatment for the areospace industry - the 40 is because they got the formula perfected on the 40’th attempt.

I do NOT recommend doing this. WD-40 is flamable…and can ignite…I’ve seen it.

WD-40 also will leave a film residue and this residue will collect dirt and this the dirt will collect more moisture.

on a serious note:

what did you do to the car in the last 24 hours?

did you fill up with gas?

did you check under the hood?

maybe go through a car wash?

think about it, and retrace your activities. maybe there is a connection.

I drove the car home last night and it was totally fine. I did nothing out of the ordinary, did not get gas, pop the hood, etc. I have decided not to spray anything and am having the car towed back to the shop that worked on the distributor last week. It feels very much like a timing problem, I’ve got my fingers crossed that this will be fixed under warranty.

Silicone spray is a dielectric. And, it’s water repellent.

“Water conducts electricity - distilled or otherwise. It’s the Ions as the article explains - don’t you remember your grade school science class?”

Yes, but pure water has very little conductivity.

0.0000055 S/m Really pure
0.055 S/m Drinking water
5.0 S/m Sea water

i may be in the minority here but wd 40 will not harm the dist. cap or wires.
Windows sweat on a cold damp day and a distributor cap can also sweat. wd 40 can prevent sweating.

of course do not spray wd on a running engine and i agree that distilled water will pass little if any electricity.

Everybody has been concentrating on the idea of WD-40 and moisture. I rather doubt that moisture has much to do with it unless the part installed was faulty to begin with. I would suspect more on the line of one of the wires is loose. This will produce the same syptoms.


What WD-40 does is it leaves a thin film on what ever you spray. This film then collects dirt…which in turn will hold water. The BEST thing you can do to keep ignition wires last a long time is keep them clean. I wipe them down with a damp cloth a couple times a year. And I’ve kept the OEM wires on a couple of my cars until I sold them well past 250k miles.

I’ve also seen someone spray too much WD-40 on their cap and it got down inside the distributor and actually caught fire…melting the distributor cap and rotor…Luckily that was all the damage.

i agree that wd can leave a film but i’ve never seen one problem caused by it.
has no one ever seen a wet dist. cap (the inside, not the outside)?
i’ve seen a few that were not only damp but actually dripping water when removed.
the caps/wires were bone dry on the outside and saturated inside

due to high humidity many times spraying the cap down with wd was actually recommended SOP when performing a new car pre-del. inspec. or servicing a used one