Hard starting or misfire after washing or heavy rain often comes from water getting into ignition parts and electrical connectors. Drying the area and applying a moisture-displacing spray to exposed contacts, with the engine off and cool, usually helps. Micron M.A.M.A Multi Application Maintenance Aid (4102) is a multi-purpose spray whose page says it displaces moisture to prevent damage and rusting and lists cleaning and protecting electrical contacts. If the vehicle still will not start, it needs a mechanic.
Why it happens
- Water ingress into ignition parts and connectors. Pressure washing, flooding and driving rain push water into connectors, coil packs, plug caps and terminals.
You will notice hard starting or misfire after a wash or rain, and over time corrosion on exposed connectors.
How to fix it
- Moisture on electrical contacts, connectors and metal parts: Micron M.A.M.A (4102). Its page lists moisture displacement on metal surfaces, cleaning and protecting electrical contacts, and rust and corrosion protection. It comes in pack sizes from 30 ml to 400 ml.
- Protecting rubber, plastic and metal parts from moisture afterwards: Micron 4500 M.A.M.A Silicon Spray, which its page describes as a water-repellent film, non-conductive, and lists engine bay protection.
The 4102 page has no step-by-step directions. Follow the instructions on the can and the TDS. General practice:
- Switch the engine off and let it cool.
- Open the bonnet and let air circulate; wipe off standing water with a dry cloth.
- Identify wet connectors, plug caps and terminals.
- Apply the spray to exposed contacts as the can and TDS direct.
- Let everything dry before trying to start.
- Try starting; if it does not start after a few attempts, stop and get it checked.
To prevent it next time, avoid pressure-washing directly at the engine bay electricals.
What to avoid
- Engine off and cool before spraying electricals. 4102: treat it as flammable until the SDS says otherwise. Keep it away from sparks, flames and hot surfaces, and use ventilation.
- Do not spray onto hot exhaust manifolds or turbochargers.
- Do not keep cranking a vehicle that will not start; you can flatten the battery and damage the starter.
- Do not open sealed ECUs or modules to dry them.
When to ask an expert
See a mechanic if:
- the vehicle still will not start after drying;
- water reached the air intake or the engine was driven through deep water, since water in the engine itself is serious;
- warning lights stay on after the electricals are dry.
Machines and generators
The same approach applies to workshop machines and generators that have been rained on or washed: isolate the power, let hot parts cool, dry off standing water, and displace moisture from exposed contacts before switching back on. If water has got inside motors or control panels, have an electrician check them before use.
FAQ
Can a moisture-displacing spray fix a car that won't start after washing?
If water on connectors and ignition parts is the cause, displacing it often helps. The 4102 page describes moisture displacement on metal surfaces and cleaning electrical contacts. It cannot fix a fault elsewhere.
Is it safe to spray on a hot engine?
No. Let the engine cool first, and keep the spray away from hot surfaces.
Will it protect connectors from future corrosion?
The 4102 page lists rust and corrosion protection and preventing further rust. For a longer-lasting water-repellent film on engine-bay parts, 4500 lists engine bay protection.
Does this apply to machines as well as cars?
Yes. The 4102 page lists industrial machinery and metal maintenance. The same rule applies: power off, let it cool, then spray.
See the product: Micron M.A.M.A 4102. Related: 4500 M.A.M.A Silicon Spray. More vehicle maintenance fixes: vehicle hub.