Misfiring after wash - soaked engine bay?

Not normal, it should not run like that. Check the spark plug cover gasket

 

Spark plug wires old?

 

+1, there is a gasket as well as a foam block at the rear, where the plug wires come out. Ensure the gaskets and foam blocks are not missing, and all screws are tight.

BTW, once you get a miss and fouled plugs, it is hard to get rid of, short of replacing the bad plug(s). My advice would be to remove all the plugs, and replace the one or ones that look bad, or have rust. Then seal everything up good. I only had issues one time with my 355 and it was because the foam blocks were missing, so I got water in the two rear most plug holes on each bank. Replaced plugs, and installed foam blocks, no more issues, even if driving in the occasional rain shower (I do live in Seattle)

 

Remove ALL the connectors and blow them out with compressed air, then hit them with a shot of WD40.

Pay special attention to the connects on the coil packs, ignition control modules, MAFS, and crank sensors. But dry out EVERY connector with compress air regardless. Oh and be sure to dry out the damn cat TCUs (temperature control units).

 

^^^This.

 

Mine would misfire when engine got wet. Turned out to be bad cat ecu. They are notorious for being sensitive to water .

 

I power wash the engine bays of all my cars including the 355 and 348 and have NEVER had a problem, done it hundreds of times on all the cars. Guess I'm lucky.

 

Too much washing, not enough driving. I almost never wash a Ferrari with water. They get wiped down regularly with Quik Detailer or Speed Shine. There's no reason to get water in the engine bay unless you need it there.

 

Why do people spray water into the engine bay?

I just do not understand it.

Asking for trouble.

Plus every bolt, connector, bracket, nut and washer goes rusty.

I never wash my engine lid nor spray the wheels.
I wipe gently with a damp cloth to remove gently dirt.

My engine bay and suspension have zero rust.

I never drive in the rain btw.

 

This.....

Any water into the engine lid is a BAD idea.....

 

My approach as well. Since I bought my car 3 years ago it's been wet washed once. Quick detailer and micro fiber towels after each outing.

 

The car is built to drive in the wet as well as the dry. If washing it with water makes the engine run badly, you NEED to know before you are on the road and catch a sudden downpour. Otherwise, you're not driving enough. So, I wash the car with water always. Then, if the motor responds negatively, I find out WHY and can do something about it at home.

 

exactly

 

Asking for trouble

Just about all the motronic 2 and 3 pin sensor rubber boots would have deteriorated....take a look at the ones on the injectors.
Water in here spells long term damage to tin connectors, etc.

 

Driving a 355 in the wet is a big no no for me

 

After putting so much time into paint correction, I wash my car with water/2 buckets.

I do it cold and dry the car and engine compartment with an electric leaf blower.

 

Usually only clean engine bays by hand with paper shop towels and cleaner/conditioner sprays, regularly for upkeep.

If an engine bay needs a deeper wash, care should be taken to cover all electronic connectors, covers, or other sensitive areas with foil before applying degreasing cleaner and any water for spray rinsing directly in the bay.

 

If electrical connectors NEED to be covered/protected, then you are just kicking an existing problem down the road...til it fails. Identify and repair any faulty connections. Perhaps that's why so many cars have electrical problems...regular maintenance of connector boots and seals has not been identified until complete failure occurs. "Too Much Care" syndrome.

 

If boots or seals appear to be degraded then of course they should be repaired to prevent any connection faults as a result of that degradation. However, I view the connectors as being designed for a nominal level of water resistance, to the degree exposed in the ordinary, normal operating conditions of wet weather driving. A hose thoroughly dousing water throughout the nooks and crannies of an engine bay, as I view it, would be an extraordinary exposure, outside of normal, where an otherwise "good" electrical fitting or component may be at additional risk. I just prefer not to tempt fate in that instance, and take some degree of care and precaution as a result.

 

It only happens to mine when I take it to the automatic car washes!

If you are missing the little rubber block for the plug wires, you better be seated when you check the price of a replacement.