Just wondering if anyone has an idea of what could be causing this.
I have a 02 dodge ram quad cab 5.9 .After it rains the truck will start fine but will not idle. Just quits. If I keep my foot on the fuel it runs fine but as soon as I release my foot it dies. After the truck warms up for it while it seems to be okay. though I have to remove my foot from the pedal slowly before it will remain idling. Then its fine after that. Any ideas?

 

Two things are possible: You have a cracked distributor cap, or a loose connection with the IAC valve on the throttle body allowing moisture in to mess it up.


Check both. Welcome to DF.

 

How is the air filter? If it is really clogged, the extra humidity in the air after rain could be constricting your airflow. Think of it like a sponge, dry, you can blow right thru. But when it's wet, not so much. It would have to be pretty dirty for this to happen, but it's a thought. After your engine warms up, it would tend to alleviate the moisture.

 

I am going to lean towards a problem with the IAC or the Distributor Cap...

 

What about a cracked plenum or the plenum gasket

 

Plenum won't have an effect on the idle in the rain. It barely has an effect in general.

 

Plenum problems only cause one driveability issue that I've seen, pinging under WOT. Other than that they burn oil.

There's an easy way to figure out wet run conditions, get a spray bottle of water and wet down Every electrical connector one at a time until the problem starts. Start with the distributor and IAC as stated above. Check map sensor, and all sensors on the intake.

 

Most issues with moisture on Magnum engines are with the disty cap.


Just sayin'

 

Thanks for the info guys. Going to look at the truck today and see what the culprit is.

 

Years ago I had a little 4x4 with the same symptom. Turns out a rubber seal for the distributor cap was missing. I'd vote for cracked cap. Do they have gaskets around the cap base?