2001 Having trouble in the rain

i have a 2001 2WD double cab that I love. For the past year it’s been misfiring when ever it rains and I live in Hawaii where it rains a lot. I’ve taken it in to my mechanic and at first they suspected 2 of my fuel injectors but replacing them didn’t help. Then they found transmission fluid leaking into the onboard computer and recommended changing that. When. I spoke to a local auto electric shop the guy said that it didn’t sound like a computer problem cuz it’s only when it rains. So now I got this truck that runs perfectly in good weather but as soon it rains it barely runs. Any ideas? Went out and got a 2017 Tundra but I’d really like to get my 01 back on the road.

 

You need to do a water test. Start with it running and use a house and start wetting down likely looking wires, starting from the bottom up until the symptoms occur. They should give you an idea where to look. Most likely its a wire with broken insulation that is partially shorting out when wet. They can be hard to find but a water test should narrow it down. Do it systematically and take your time, you may have to let the truck dry and repeat it as you narrow down the area.

Without knowing anything else though I would look into the oxygen sensors. A failed primary sensor (the ones before the cat) can cause the truck to go into limp home mode which it sounds like yours may be doing.

If this happens every time it rains this should be pretty easy to find with a hose test.

 

Thanks for the help. Just clarify, pop the hood and spray water in one area at a time to try and localize the area and then repeat to close in in the culprit?

 

Sounds right. You may even try a spray bottle of some kind to close in on it if you think your close.

It may be something lower to ground. The upper area under the hood usually does not get very wet.

 

My old 90 F150 would shut off when I had a bunch of water hit it. Turned out to be the plug wires. I’m sure your mechanic checked that. Just offering my .02

 

Same with an older ford I had. Spark plug wires.

 

Thanks everyone. I’ll let you know how it goes!

 

Yes. Although since water runs down you want to start at the bottom and work your way up. If you start spraying water form the top you will have no idea if the issue is at the top of the engine or the bottom or what. The idea is to find the area where the problem is and then let it dry and then come back that that area and wet down specific spots until you find it.

For instance, if you find it only happens when the left side of the engine bay gets wet then let it dry and then come back and start wetting down sections of just the left side.

 

When the misfiring occurs, does the check engine light come on or not? Do you have any codes? I'd at least get a code reader and check to make sure, as it would help with ID'ing the issue. It would be helpful to know which cylinder(s) are misfiring.

If the CEL does not illuminate or a stored misfire code on a particular cylinder, I'd then wait for a hard downpour and then try to pull into a garage or cover and open the hood and check the engine bay for where the water is getting into. That will most likely point you to the right direction.

Does the misfiring happen after driving (water getting into all sorts of different areas) or just after sitting in the rain?

My first thought would be water somehow getting on the coil packs, but that's a long way for water to travel. I'd check the components around the outer perimeter of the engine bay (DS fuse box etc).