missfire in rain?

[low330]

I was driving home today on my 12 mile commute from work and it just rained by me and well 2nd through 4th (that I've noticed) between 2-3k rpm I get this real bad missfire. This only happens in the rain too and just started happening maybe 6months ago and still can't seem to figure out the problem. I've done sparkplugs less then a month ago (yes gapped correctly), wires cap and rotor was replaced like 2 years ago (but maybe driven for a total of 9months.... Long story with storage and other cars and whatnot). The ignition coil was replaced with an msd coil along with the wires cap and rotors because a guy I no was selling it cheap. I should also Prolly say I never ran an o2 sensor in the 4 years I owned it and just reciently installed a Denso o2 b.c.... well Idk why lol and it seemed to not like it that's when I can kinda narrow down when the problem started. Since then I took the o2 back out and ran fine.... Until it rains. Any thoughts? And sorry lol its an 86 eta

[coldweatherblue]

check C191 connector beneath the intake manifold. It is a screw on connector (7 pin) that connects the injector and coolant temp sensors to the DME. It gets waterlogged and corroded and often fails in wet weather.

edit, disregard. just read you have an '86 so you don't have c191.

[crazyman]

Could be getting moisture in your cps sensors. When I bought my first ETA I took it to a car wash and it did the same exact thing. Never went through one again, when I discovered that's happened.

[Kozworth]

See, what I was thinking was more or less the wires/ig coil. If you have a crack in eithor, moisture goes in there and of course electricity follows the path of least resistance. The spark will follow out through the water, and not to the engine, causing the miss.

What I would do is fill a spray bottle with water. When its dark, pop the hood and idle the car (or you could get a friend to rev to 2k or try to zip tie the throttle open). Spray around all the wires, cap, and ignition coil. If there is a crack, you should see a small arc. Replace as necessary.

[crazyman]

The only problem is that you could short out the ignition system. If there old enough to run the slight possibility of being cracked like that, you might as well replace them. The other thing is the engine in neutral will rev different then while it's under load. I.e. throttle position an timing ect.

[Kozworth]

Well, not sure about the shorting issue. Ive known many mechanics that have used this method to make the car "stumble" to confirm a complaint. Whats the difference between a spray bottle shorting out the ignition system, as compared to rain? Pretty much nothing. That would be like telling the OP to not drive the car in the rain because it will short out the ignition system.

And for reving, the Throttle is actually the same via neutral or under load. Its a potientonometer (spelling sorry) that changes resistance according to throttle opening. Timing might be different according to cts, iat, etc. But just an idea to try out, whatever you can do to reoccur the symptom inorder to diag it better.

[Cephas]

Could be getting moisture in your cps sensors. When I bought my first ETA I took it to a car wash and it did the same exact thing. Never went through one again, when I discovered that's happened.

Ha, yes! This happened to me as well. Good times with the old eta bellhousing sensors.