my truck has developed a strange issue. it runs fine most of the time but when it rains or snows or the road is real wet it misses, and even died once going down a hill at idle. throws the check engine light after the 3rd miss but by the time I get somewhere I can check it, the light is out and the reader says no codes are stored. it's not a frequent miss either, maybe 3 or 4 times between home and work, about a 20 mile drive. I'm completely lost on this one guys. any ideas??

 

Humm, to start, the missing and rain are all symptoms of the CPS. It's a $14 part (Only buy the FORD product) and swap it out.

Others might have additional comments or suggestions.

The CPS is located on the front of the block, lower passenger side. It's held in place with a 10mm bolt. The electrical connection is a simple two wire design. Easy to swap out. It's good to keep a spare in the glove box.

 

I would start looking around the main electrical connections around the motor (valve covers), PCM at the fire wall and the connection in the fender well to the IDM. Look for corrosion in these connectors. As mentioned the CPS or heck any exposed wiring could be causing the issue.


Any chance your drivers side windshield is leaking down on your GEM/PCM/Fuse Box? A rusted emergency brake hardware under your dash is a good indicator of your windshield leaking. Ask me how I know....

 

does is have cab(clearance) lights??

 

Tried changing the cam sensor a while back and no dice. Haven't noticed any water or corrosion and I've had the pcm out several times but I will check again. Have any pics or more info about the wiring in the fenderwell? That sounds like a likely culprit

 

And no it does not have cab lights

 

Are you using an aftermarket cps? If so, the wipers can cause interference. Read through this thread https://www.ford-trucks.com/forums/9...werstroke.html

 

I have a 2003 f450 7.3 that had a cab light leak and it leaked right down on the fuse box (not the pcm) and killed the truck...would start up when the water dried...

 

Moisture getting into the connections of the CPS will do this. Seal it better where it going into the engine and where the connection is.

 

Here is a pic of the location of the IDM. I would exhaust everything else before going here as it's not fun to pull out and re-install. You don't need to remove the fender ha ha just the splash guard. Surprised they couldn't find a better location for this.

What are you using to read codes? Shouldn't a code be stored if the CEL has come ON at any point?

 

I would first go for a good long test drive on a non-rainy day and determine if it is indeed the rain that causes this or the windshield wipers. Run the wipers during the test drive being sure to include all speeds and intermittent settings.

If you can duplicate the symptoms with the wipers running on a clear day, then you either have a CPS or ground issue.

Often times it's not the water but the interference of the wiper motor signal with the CPS signal that causes this problem.

 

It is an aftermarket cps, I hadn't even thought of it acting up. I'll check that out when it gets light again. I'll also get into the fender. Had no idea the was in there haha I've tried to duplicate the symptoms in dry weather but haven't been able to so far.

 

And I've been using a superchips programmer to read codes

 

And it ALWAYS has 2 codes. Intake air temp circuit low voltage and ebpv circuit voltage high. I don't expect those to be related but I'm still learning about these things haha thoughts?

 

Should go OEM with the sensors