Still chasing down the intermittent stumbling on the L05 V8 in my 93 FWB. Changed out the spark plugs because that was easy/cheap. Everything is fine afterwards, so I took it to the car wash today, and immediately afterwards it stumbles like it's misfiring and there is a lot of popping from the exhaust. Now I definitely know it has to do with being wet - it only happens when it's damp out or when I give it a car wash.

What are the chances that the distributor needs replacing? I can't visually see any cracks in the cap, but I also heard many cracks are hard to see anyway. Should I start with the cap? Whole distributor? I'm completely lacking in instinct here - other cars I work on have those modern distributor-less ignitions.

It's not throwing any codes either.

Thanks for the help all.

A cap, rotor, wires, and plugs will fix it. In the meantime, pop the cap off, and spray everything inside and outside the distributor with WD40. That will cure the wet stumbling issue for awhile...

Oops, meant to say I changed out the plug WIRES already. Thanks for the WD40 trick - I'll definitely do the cap and rotor then, and look towards the plugs soon.

My LT1 is doing something similar, if I drive through some heavy snow I get some missing, then eventually it goes away. Crap, -8F expected tonight, no going in to "fix".... And not real fun on an LT1 either....

NODIH, try changing the vaccuum harness on the opti. It's the same on your 94 D body as the pic below...

http://shbox.com/1/opti_vacuum_harness.jpg

I'll stick my gauge/pump on and see if it still has integrity, thanks! I check periodically but that is a very good idea.

We had similar issues on both our L05 Roadmaster and Fleetwood...and in both cases it was the distributer. As can be seen, and as I read was common, where it's at (under the cowl area) can be susceptible to extra moisture and that affects the distributer more when it's already starting to fail.

Replaced the cap & rotor on both (cheap & easy compared to my LT1...hah...), and all issues were fixed and remain fixed.

I should add that I had a similar experience with my 92 L05 Roadmaster wagon. Two years ago, we went away for Christmas, and the weather was very mild and damp. When we got back, my wagon was very hard to start. Once started, it was misfiring terribly. Cap, rotor, wires, plugs, and all was good. Mileage immediately improved, as well.

Just fixed this EXACT problem on my L05 caprice. Someone mentioned that they once had their distributor crack in their truck which allowed moisture to seep into there. When cold, all the moisture would condense at the bottom of the distributor and when hot the condensation would vaporize all over the contacts at the top of the cap all over the contacts. I used this information and checked mine... no cracks but somehow moisture had visibly got in there... contacts were destroyed and covered with that white crust... replaced cap and sealed up with some goop and voila!

If it is not the cap (which is what I would try first) Your connections between your wires and plugs may be dry and decrepit... may be arching to a nice wet surface on the engine. I recommend taking off all of the wires and applying dielectric grease to all of these contact points to make sure there is no possibility for arching.

Don't worry... I had the SAME problem!

+1 on the dilectric grease. I bought a tube of that stuff over 10 years ago, and it stays in my toolbox and sees regular use. I don't think it will ever run out! Invaluable on battery terminals, too!

checked, 4inches of vacuum on it, I pumped some on the vent side, it went up to 10ish and then dropped off, sounds like it froze up on there, ice maybe? Or ice knocked a line off. Will have to work on it ASAP....

It built up like I expected, just didn't get up to 15+ (minus?) inches....

I'll stick my gauge/pump on and see if it still has integrity, thanks! I check periodically but that is a very good idea.

Looked at the FSM and the cap is EASY - two screws. Went out and bought it for $16 and I'll swap it out when the weather gets better here again.

Rotor looks a bit more involved? Would you have to remove the distributor and re-adjust the timing? I'm sure it'll make more sense once I pull the cap off and take a look at it.

Plug wires I bought looks like they already had some sort of grease on it - I assume it's dilectric. Took a spray bottle at night and watered down the plug wires really good the other night and I don't see any arcing so that's good cause these are brand new wires!

Looked at the FSM and the cap is EASY - two screws. Went out and bought it for $16 and I'll swap it out when the weather gets better here again.

Rotor looks a bit more involved? Would you have to remove the distributor and re-adjust the timing? I'm sure it'll make more sense once I pull the cap off and take a look at it.

Plug wires I bought looks like they already had some sort of grease on it - I assume it's dilectric. Took a spray bottle at night and watered down the plug wires really good the other night and I don't see any arcing so that's good cause these are brand new wires!

Rotor pulls right off, it is just pressed on by hand into a keyed slot. DO NOT remove the distributor to adjust timing! It is set at 0 degrees from the factory and the computer does the rest, this is not a carbureted engine! If your wires and plugs are good that leaves cap and rotor... if not those there are other options but it is probably those!

Rotor pulls right off, it is just pressed on by hand into a keyed slot. DO NOT remove the distributor to adjust timing! It is set at 0 degrees from the factory and the computer does the rest, this is not a carbureted engine! If your wires and plugs are good that leaves cap and rotor... if not those there are other options but it is probably those!

Wow, that rotor was so gunked up... snapped a couple pieces off of it (oops), then sprayed it down with WD40, and took some vice grips to it and it off it came. With all the gunk on it I'm not surprised no spark got transmitted when the dirt in there got wet. But yes, it's just pressed on by hand into a keyed slot - thanks for the info! For some reason I was misled by the wealth of information in the FSM to think it was more complicated. So far so good - car seems to run pretty well now, I'll post up if it rains and misfires again :lol:

There is always the garden hose if you live down south, instant rainstorm.... Here, you don't even think about using a hose this time of the year.... 6-12 inches of snow expected in the next 24 hours with 1/2" of ice first...

Don't get too nutty in there with water though, simulate rain dampness of the rain, not direct spray of it all.... Then you can see where the intrusion is. I have seen hairline cracks be a real bugger....