Stumble on the highway

[cam.man67]

Hoping y'all could help me out here. The car runs fine at idle, around town, etc. but randomly will start missing once warmed up good on the highway.

My first guess is ignition related since this just started after my wife took it through a car wash. I'm assuming something got wet, but haven't found anything to corroborate that. The distributor is dry inside (even sprayed it with wd40). Coil and ballast are both a year old and test fine, plugs are relatively new and look fine on inspection. Plug wires are also fresh.

So, should I rule out ignition and look into fuel-related?

 

[NudeHemidude]

Try replacing the fuel filter.
It may be dirty enough to start being restrictive at highway speed.
I once had a car that ran fine under 3000 rpm but started missing over that.
I changed the fuel pump and all kinds of things before a $5 filter solved the problem.

 

[kiss]

A random miss like that could honestly be anything. I was battling one for 2 months and it turned out to be my PCV valve. Don't ask me how, I have no idea. I would definitely change your fuel filter and check all electrical connections.

 

[slantsixdan]

Use the clues at hand. It started right after a car wash—that suggests a water-related fault. Probably ignition-related as you suspect. Does this car have electronic ignition, or breaker points? Sometimes water can hide in liquid form until things get warm enough to turn it into steam, then it makes problems. I've even seen water get via the bowl vent into the carburetor at a car wash and make random running problems, but that was a do-it-yourself car wash used to pressure-wash the underhood area; I doubt if such a thing could easily happen at the drive-thru type of automatic car wash.

At first, don't get sidetracked by the many potential causes of poor running that couldn't be caused by going through a car wash. It's possible the problem is just coincidental with the car wash, but it's more likely water got somewhere it shouldn't and hasn't escaped. Either end of spark plug wires, distributor condenser if it's a points type, etc.