i have a 99 f350 7.3 psd. I was driving to town and it developed a slight miss at idle. Started out slight just at idle and now it will drop about 200 rpm when it misses and is at idle and on up to red line. it has very slow throttle response one time i rev it up and the next throttle response is like it should be. I do not have an SES light. Any help is greatly appreciated Thanks Justin

 

Last night I put a new cps in it (grey) but it was all I could get at the time. Started the truck Up and it ran worse then before. Put the old cps back in it It's grey also and truck ran perfect. Idk of its the sensors causing this or if there is a short in the wiring harness to the.cps. last time it messed up like this it.was raining like crazy I changed the cps and haven't had a problem till now. It stormed bad yesterday but the truck was inside during the storm. I hit a few big spots of water yesterday morning but truck didn't start acting up till last night

 

any ideas? I was driving home tonight had the chip in 140 and was getting on it pretty good and truck just lost all power turned my chip down to 80 econ mode and couldnt maintain 60 mph in 6th gear down shifted to 5th and it held 55 mph flat to the floor and boost was 10 psi egts were around 600. ses light would faintly come on but never would come on full brightness and stay on, just flashed. truck idled fine, shut it off and restarted it and it didnt just fire off it kinda slowley picked up. shut it off again and restarted and it fired right up and ran fine went and drove it and it ran fine till i got on it then went back to no power.

 

I am not an expert, and I don't want you to start throwing parts at the problem based on my response. My response is mainly to let you know that the FTE Brotherhood is not ignoring your post...

Did you put any dielectric grease around your CPS when you re-installed? If not, there could be moisture in there causing the problems. Also, check your IPR and IDM to make sure there is no moisture in either. The problem with "running rough when raining" could be a host of problems. If any of your wiring was rubbed-through, it could cause problems.

Check your ICP sensor, make sure it's connected well, make sure there is no water in it...and if there is a lot of oil in it, well, it's time for a new one. It's on the top of the engine on the driver's side, so I wouldn't *think* it would get getting much water or moisture in it, but it's a simple check by unplugging and looking (don't lose the little o-ring on the connector when you removing the wiring harness).

Hey...based on your 3rd post...do you have a fuel pressure gauge? It almost sounds like might have a fuel pressure problem. Could be debris in the line, or a broken pickup foot in the tank, clogged screen, etc. If you're tank is low on fuel (below 1/4), it's a small possibility.

This is all just a quick comment...don't take my word for it as gospel. I'm sure someone will chime-in with better diagnosis.

 

Today i ohm tested the wires for the cps they ohmed out at 0.3. tommarow il check the idm connector providing my truck will run to make it to work. This week im ordering a new ipr and icp sensors also ordering black cps. No i do not have a fuel pressure gauge but i work at john deere so il be able to test it tommarow after work. Fuel tank is full it never gets below half a tank.

 

Went to go to lunch today started my truck up and it was idling rough and missing, shut it off started it back up did the same thing. Shut if off let it sit for a min and fired it back up and its running fine.

 

Have you ever pulled your valve covers? Your under valve cover harness (UVCH) may have pulled out partially underneath. It's a very common problem, especially if you've never gone under the VCs. That's what the "50 cent" mod is for, to shim the snap that locks that connector in place. If you have the original wiring harnesses and gaskets, it would not be surprising if they are loose. They may even need to be replaced. You can ohm the pins from the outside connection without having to remove the VCs.

Also, what about your GPR? Is it original too? This could also be the problem.

Of course, these issues would be re-occurring whether it was wet or dry, so my initial response was due to your comments about the rain.

I don't know about buying all those parts. Don't throw parts at a problem until you know it's needed. Not that it would be bad to have them on hand for the future (if you have the money to buy in advance). I can't believe no one else has responded yet. It'd be nice for someone near you with AutoEnginuity to come do a quick diagnosis. Let's keep our fingers crossed.

 

Well all the parts.will be used on my other truck if they aint the problem on my dually and it does not do it all the time. If its messing up i can shut it off and start it back up and it will run fine.

 

How's your oil level? Is it time for a change? What about the fuel filter? Changing the CPS may or may not give us a clue. It could just be one of those freak coincidences. Where did both the CPS come from? Ford or aftermarket? If you start the truck and let it idle, and then VERY CAREFULLY wiggle the cps harness while it's running, does the idle change or the truck start to or stop missing?

 

right now it has the cps in it that was in it when i got it. i do not know if it is original or not the other one i got is aftermarket. oil level is full mabe 1000 miles on an oil change, fuel filter is new changed it this past weekend. i have not wiggled the cps harness to see what it does while its running. Yesterday afternoon and today the truck has ran excelent without any problems. im leaning more towards its a sensor or a wiring harness. This weekend if i get the time im going to get a garden hose and soak everything under the hood while the truck is running and see if my problem comes back. if it does then im getting moisture somewhere. cuz the problem came back after the storms we had last week. but i also think there is a sensor going bad or acting up to.

 

Did you figure it out? I hope so.

By the way, I didn't mention it in the first post, but just saw on another thread a similar problem...which is water running down the windshield getting into the GEM. I sure hope that's not your problem, but always a possibility. You don't happen to be getting water into the floor of your truck when it's raining (like on your Emergency brake pedal, or that area) do you?

 

Hmmm.... Storms have low pressure. If you have a MAP or EBPS on the ragged edge, the low BARO reading might be enough difference to trip the truck - just thinking aloud. Look at the last link in my sig and see if there's any help there.