Skip the auto shop - Our mechanics make house calls

Q: Unable to start after it rains or misfires until the engine heats up in high moisture conditions

asked by on

After a heavy rain the van will not start it will turn over but not fire. If there is a heavy dew in the morning or a fog situation it misfires until the engine heats up after that it runs fine. I thought the hood gasket may be worn out allowing water in the engine compartment so I replaced it and the problem persisted. I cleaned the Mass Flow Valve with the spray they make for that and that didn't do it either. Is there another sensor that I should be looking at?

My car has 115000 miles.
My car has an automatic transmission.

A: Hey there. This misfire no-start in wet or ...

Hey there. This misfire no-start in wet or damp weather is going to be caused by the ignition system of the engine. In order to isolate the cause you can remove the inside engine cover and then start the van.

Watch the ignition wires, coil, and coil wire for arching while using a spray bottle with water to spray a fine mist of water on the ignition system in small areas at a time to find the cause of the engine misfire and you will get a misfire or stall when the spray then causes a miss. You most likely will have an ignition coil and plug wires that are arching to ground. After the cause is found, then I would recommend replacing the distributor cap and rotor, plugs and plug wires and the the ignition coil. This should repair the problem for you and the engine will run better altogether with a fresh tune-up.

Was this answer helpful?
Recommended services
Get a Quote

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: A/C cooling fan only starts working at 93 degrees

There doesn't seem to be past information on the A/C not turning on until 93 degrees for a 2011 Mercedes Benz S550. I would try to see if the automatic temperature control is set to automatic and dial temperature to...

Q: After numerous no-starts on rainy days I've decided to replace the distributor cap, rotor, sparkplugs & wires.

Hi there. What made you determine that the parts you stated were the cause of the no start? If these parts fail, an engine drivability concern quickly follows. I do not feel confident that replacing these parts will alleviate the...

Q: Trailblazer 04 vibrates while in Drive or Reverse. There is a raw gas smell on the exhaust.

Hi there. Check the spark plugs on the engine and see if they are fouled out. A fouled out spark plug will cause the cylinder to not fire and let the fuel that is sprayed in go out the exhaust...

Related articles

P0052 OBD-II Trouble Code: HO2S Heater Control Circuit High (Bank 2 Sensor 1)
P0052 code definition HO2S Heater Control Circuit High (Bank 2 Sensor 1) What the P0052 code means This code is seen when the Engine Control Module (ECM) tries to control the...
Rules of the Road For Iowa Drivers
Driving on the roads requires knowledge of the rules, many of which are based on common sense and courtesy. However, even though you know the rules in...
How to Avoid Back Pain in a Car
If you have back problems, sitting in a car for an extended period of time can be excruciating. Even without back problems, you could experience discomfort and soreness from...