Misfire in Rain

[Mike]

My Rev 2 Turbo isn't happy in the wet at the mo. If caught in a downpour whilst driving or left ourside in the rain overnight it seems to misfire until it dries out. I suspected the coil pack so changed that and the spark plugs at the same time but the issue remains.

I'm sure I've heard people talk about this before but I cant remember what the usual culprits are. The alternator is new by the way.

Thanks

[aussieGT]

Have you had a look in the spark plug wells? Mine had a misfire in or after rain, one of the caps on the plug 'tower' (rubber flat thingy that sits on the cover) wasn't sealing right and let the spark plug well fill with water.

That was until the engine got hot enough to cause the water to boil and evaporate away.

[2barGee]

My Rev 2 Turbo isn't happy in the wet at the mo. If caught in a downpour whilst driving or left ourside in the rain overnight it seems to misfire until it dries out. I suspected the coil pack so changed that and the spark plugs at the same time but the issue remains.

I'm sure I've heard people talk about this before but I cant remember what the usual culprits are. The alternator is new by the way.

Thanks

I had this issue and it was water getting into the dizzy cap

[Dame]

How old are your HT leads? Are they genuine Toyota?

I've had missfire problems twice in the rain, particularly when coming on boost (when the engine is under strain). In both cases it was replacing the HT leads that solved the problem for me, but obviously they're the most expensive option, so I'd start with the cheaper stuff first i.e. check plug holes / plugs, dizzy cap, rotor arm. If you do replace the HT leads, I would probably go for OEM - most expensive but very reliable!

[Mike]

Leads are genuine Toyota, a few years old but very few miles on them and the car is garaged so very little wear and tear or exposure to the elements. No sign of water in the plug wells, and the plug are brand spanking NGK BKR7Es so should be ok. Coil is new, I'm starting to think, dizzy or king lead. I bet Toyota doesn't sell the King lead separately......

[Willenium]

Do you have a cone air filter on it? I used to find that any rain getting onto that can cause a bad misfire until it dries out. I've also had problems with one of the HT leads breaking down and causing the spark to jump from the dizzy cap to the nearest conductor (whether that is you or an engine part).

As some of the guys above have found though, a friend of mine had a bad misfire and I discovered cylinder 1 plug was standing in water. Dried it out with some paper towel and it was fine.

[jimGTS]

coil pack too can get wet.

(some crack!)

[abovetherim]

When you fitted new coil did you clean up the bracket for it and the fixing points of the ignitor and the bulk head it bolts to. It earths through the bracket.

Also king lead cold be an option. I had one break internally. Yes Mr T does sell them separately.

Look for hairline cracks in the dizzy cap and pull of the rotor arm and inspect that.

Finally pull each spark plug and inspect the porcelain part as well as the tips. The porcelain can crack

[Mike]

Having driven from Bath to London this morning in conditions Noah would be familiar with I can confirm that the car now runs fine in the rain I've changed the distributor, rotor arm and King lead, so it was one of them although I can't say exactly which one.