Whenever we have rain, my truck seems to have difficulty starting. It will start, but when it drops down to idle speed, it dies; i.e., it won't idle. If I restart and hold down on the accelerator, it will stay running, but if I let off the gas, it dies. If I do this and hold the accelerator down, it will eventually idle (after about 20 seconds). Any ideas?

 

Maybe you could give us some details about your truck, such as year and engine size? If we tried to help you without those details, we'd just be spinning our wheels.

 

Sorry; It's a 98 XLT extended cab 4.6 V8. This problem just started happening at 64k miles.

 

You don't state what year your truck is, but if its an older model, you can bet that it will be somewhere in the ignition system. Look for cracks in the distributor cap that would permit humidity and moisture inside. Another common problem is old spark plug wires that end to leak voltage in high humidity conditions... ie, rain.

 

'98 4.6L with 64k miles. I'm with BeastRider and will guess it's the ignition system. Probably the plug wires need changing. How to check it? Get a spray bottle filled with water. Make it go as fine as it will go and with the engine running, start spritzing the plug wires. If the engine dies, you've found your problem.

Sometimes, you can even see the arcs between the wires at night.

 

My 99 5.4 also had problems keeping an idle when it was cold outside or had rained. It turned out to be the Idle Air Controller. The dealer replaced this part and I have not had a problem since. It even smoothed out my rough idle. There are many threads about this, so do a search on IAC or Idle Air Controller and see what you can find.

 

MarkS:
Did the dealer tell you, or would you happen to remember what position the IAC was stuck in (assuming that it was)? Just curious...