I have searched and read lots of miss fire threads but have not found this exact problem just yet. So here is another miss fire thread with hopefully key info the help sort it out.

Background. In 2012 I replaced all the plugs and Cops. Used Ford parts. Here is the thread https://www.ford-trucks.com/forums/1...l#post11824803

The truck purred like a kitten after that plug changed and I had forgot how smooth this engine is. Now to the problem.

I am having random miss fires under this one set of conditions.


- I am towing my 32 foot travel trailer, GCW (truck and camper) 17,100#
- This miss fire only happens when after the truck is hot. Towing approx 2 to 3 hours
- Problem only happens in eastern PA and pulling long hills. I have not been to other mountains to test this under the same pulling.
- Problem does not happen any where in Ohio or NY.
- I tow a flat bed trailer with tractor, 16,000 GCW here in OH and I cannot recreate the problem, even burying the pedal to the floor at any RPM.
- When I hit that mountain range and the problem starts acting up, I can feather the gas pedal and ease up to 3,600rpm and there are no miss fire most times.

- If it is in cruise control and I get a fast down shift, heading to 3,800 to 4,200 rpm I can often get a random miss fire. Same thing if I use my foot and it down shifts up from ~ 3,600 to 4,200.

- This only seems to show up at approx 3,800rpm and above. 3,600 and below, most never.
- It takes about 2 hours towing from an overnight cold start before this shows up.
- The miss fire codes go in and out on the check engine light. The issue moves around. Not always the same cylinder
- I ended up plugging my scanner in, leaving it live on the seat to watch the codes come in and out and the check engine light not come on.
- I am puling 50 to 55mph up hill when this starts acting up


Now I do when this starts acting up bad enough.

- If I get a cylinder specific code I pull into a rest stop, take a break, let the engine cool down, pull the COP and check the plug. The plug has always been good, clean burn. I spray contact cleaner in the COP connector, clean it up as good as I can at a rest stop. Put it together and head out again.

- Still in the same mountain area and now it comes back, just another cylinder in about 30 minutes time. I have also changed a new Cop for an old few spares I have in the truck. They run on the old ones. Many times I get no cylinder ID, just random miss fire so I do not know if the old ones are doing this or it's a new one.

- I did put some dielectric grease on the connections thinking this would help at the time of rebuild in 2012.

- This issue will not come back again until I repeat these same long pulling hills.

- This issue has repeated in the same place for 3 years in a row now. I did not use this route on the old COP's so I do not know if it is an issue with the new Cops

We are heading out in August this year again through the same area. I'm trying to find something to fix before then.

As a proactive approach, in the campground at night I cleaned all the connections as best I can. Have no compressor to blow them out, contact cleaner sprayed in and rag clean. This does not seems to shift the problem.

I have 20,000 miles since the plug Cop change and it will not do it here in Ohio, IN or NY. It needs the right higher heat pulling to show up.

Even at these temps and pulling, the issue very rarely does this under 3,600rpm. How 3,600 can work and 3,800 not, is mystery.

The only thing that I think maybe ding this, is the dielectric grease has some effect when the truck gets hot and for a split millisecond I loose connection at the COP.

Given these conditions, it this something other then a connection issue? Do the Ford Cops break down under higher heat?

If it was fuel related, I would think it would show up here in Ohio pulling my flat bed or the camper.

If it is vacuum related how does it know what RPM I'm at? Is there really a lot of difference between 3,600 and 3,800 or higher? It's that fine of a line of working and not working.

Any thoughts, much appreciated.

Thanks

John

 

I think the '3800rpm only pulling heavy trailers uphill' is indicative of a specific engine load.

Lots of factors involved in engine load
-rpm
-vacuum
-throttle position
-type of fuel
-temperature of intake air
-temperature of coolant
-travel surface: uphill or down
-vehicle speed (wind resistance, rolling resistance, trailer factors)
-and probably more that I'm not thinking of.

If you can get live data then you should watch air/fuel ratio, exhaust o2, exhaust temp, injector pulse width, fuel pressure, etc.

You have an "everything problem" and therefore you need to carefully watch everything.

Keep us posted- whatever you find will be helpful and interesting to the rest of us.

 

Have you cleaned the MAF? And, make sure the intake temp reads correctly.

Not sure what else to say - except MAYBE fuel pressure is playing with you. The long, hard pull points to something fuel or mix (MAF) related, especially with the random misfire, but then, it's also heat.

Do you FEEL the misfire? Or is it just throwing a code for it?

 

Hi Im50fast,

Thanks for your response. I will look into the live data. I need to build a data base of that data here in OH where the truck runs OK and then compare it to when the problem starts.

Yes, the issue does acts up in the 3800 and above range but there is more to it. It is not just the RPM, it takes a long pull, up hill, to create the heat in the engine compartment that seems to be a trigger. I can run the truck with the camper or my flat bed with similar weights and I cannot get it to fault out here in OH, IN or NY. I have 20,000 miles on the truck since the plug and COP change and it has not acted up until I create the long pull, up hill and after the engine compartment gets hot enough. And even in eastern PA, it takes this long pull up hill area to show up. Something is on the edge, and the heat I think pushes it over the edge. If I ever find this issue, I will report back.

Thanks

John

 

Hi Krewat,

Thanks for your note. I'll insert answers in your reply.

When the truck acts up enough to throw a code on a specific cylinder and I pull into the rest stop to fiddle with it, I really do not know if I'm doing anything changing the COP or cleaning up the connection. The truck is cooling down and that may be what is helping it. Granted when I start back out, the cylinder I had the issue with, goes away. At least for that one time. I have not yet created enough repeats on the same cylinder to realize a pattern. I'm going to have to start a log book on which cylinder throws the codes by time and date and what I did with it afterwards.

My window to trouble shoot the problem acting up, is about 2 to 3 days while I'm towing. Once I get out of that area, the problem goes away.

I'm trying to find a list of things I can rule out before the trip and then be prepped for on the trip. The hope is, next year I may head west where there are real mountains... I'm hoping to get the truck sorted out before then.

Thanks

John

 

Man, that's a frustrating problem. I'm in the middle of troubleshooting a misfire myself. New plug boots are in the mail and will get installed hopefully this week.

A couple comments:

- From reading part of the OBD-II book for my '99 V10, my understanding is that these engines check for misfires of all kinds by sensing the acceleration of the crank shaft via the crank position sensor as the engine goes past a particular spot each time a cylinder should fire (like 10 deg past top dead center). This allows the computer to know when the cylinder misfires for fuel, fire, or compression.

- It sounds like you've got a good scan tool, so this probably isn't required, but I recently got info back from Linear Logic explaining how to use a Scangauge II to read misfire counts. Info is here, in case it does you any good: https://www.ford-trucks.com/forums/1...e-monitor.html.

 

Hi CornFamer,

Thanks for the info on the sensing system. I will have to dig into that more.

A question I do not know, yet anyway, I had thought a misfire code was ignition related? That might be a bad thought. I'm not getting an injector code, at least yet. I get P0300 or P0301 up to PO310

Digging into that I get this. Which if this is accurate can be O2 or an injector. But again, this floats around like a global issue and is aggravated by heat.

http://www.obd-codes.com/p0301

I'm "gonna" learn something for sure on this.

Thanks for your reply. Hope your search mission comes out well.

John

 

Misfires are detected by monitoring the crankshaft as it spins. Any slow-down (or lack of acceleration) at the wrong time means that cylinder isn't firing.

It can be ignition, fuel, compression, anything could cause a misfire code.

 

Thanks Krewat, This helps at least know how the truck is creating the code.

Now knowing this, this is not simple... I will have to see what my scanner can read in live data and start backing into each area. Process of elimination.

I had thought for sure the dielectric grease on the connections or the new COPs I added may have had something to do with this. In this case, maybe and maybe that has nothing to do with it.

I'll let ya all know how the hunt goes. Anyone else with ideas, I'm very open minded to listen.

Thanks

John

 

 

Sam, Thanks. I have some cleaning to do.

 

Can you actually feel the misfire? Or are you just getting random misfire codes? I ask because the harmonic balancer on my V10 just came apart, and I think it had been running "loose" for a while. A separated damper/balancer could definitely confuse the computer...although I don't think it would happen only under certain conditions like you have described.

It would be nice if you could have the truck put on a diagnostic machine/scanner and see what the fuel trims are, etc. A lean condition can cause misfires.

Cleaning the MAF is cheap & easy.

 

On this topic----while Sam's video is great it applies mostly to those types spark plug terminals where a single coil is the high voltage source; COP's are quite a bit different in that their energy is developed much closer to the actual plug and delivered much more efficiently.

Dielectric grease if applied to an individual terminal mating pair of a typical automotive connector will be wiped away when the connection is made. That's by design of the mating terminals, the connector shell simply holding them close together and relieving any mechanic stress trying to pull them apart This isn't saying an over use of dielectric grease is good---the right amount in right location is always best.

In this case I'm of the opinion its not contributing to your issues.

 

Hi,

Thanks for the tip. I will keep that in mind. I'm collecting and all suggestions.

Yes, in some cases I can feel the miss fire. For the 1 instant random missfire's, I can only see it fly going in and out on my scanner sitting on the truck seat. When the truck actually get's enough of them to throw a check engine light, and it will throw a specific cylinder code, it will stumble enough I can feel it. The engine then starts to stumble.

I have not yet dug into the fuel system. I had a miss-conception that a miss fire was "only" ignition. Now I have learned it can be fuel and O2 as well or anything that did not create a complete combustion on that stroke.

And yes, cleaning the MAF is on the list.

 

Hi JWA,

Thanks for your thoughts. They are taken well. I have been wracking my head on how I may have disturbed something.

In this case I may have messed up with the dielectric grease. I did the actual control connection and the spark electrode connection. The high voltage connection it should, or thought it would, fire through it but the control connection, well I do not know.

For reasons not yet understood, this issue does not rear it's ugly head until I get the engine compartment hot enough and then I'm in a heavy pulling situation that seems to align "most" times when I'm at or above 3,800 rpm. Even on this same pull, if I let the speed drop and nurse the engine to not down shift, it greatly lessens the miss fires. For me, this is only in eastern PA on a certain long mountain pull to create the conditions. Around here in the flat lands of OH or even mountains of upstate NY, it just does not show up even if I get up into 4,200rpm.

Why I was challenging myself was the COP control connection. If under high heat, the grease flows enough when hot that it insulated the signal a few milliseconds to not get through, thus no firing of the plug. But yet 3,400 rpm being nursed verses a hard snap up to 3,800 does may trip it, made me question that can it be the grease?? 400 rpm for a limited time is not a lot of heat difference.

And yet, it never does it that I am aware of for 20,000 miles since the COP/plug change here in OH. I'm on the edge. Ignition may have nothing to do with it but it is a variable for sure.

I will eliminate this one variable as it has a potential at least. Contact cleaner and compressed air and keep at it while I have the time home and not in a truck stop out on the road. And I can do it before our August trip.

Thanks again, open to all sides of this perplexing issue.

John