Intermittant miss fire

[IC2]

Oh my, a Ford V10 in a country that has never seen one can be a challenge.

As others have said, there is a very good chance that a COP is at fault but attached to those coils are 'rubber' boots and a spring like conductor that should also be changed at the same time, While the spark plugs may also be a consideration, they will seldom cause a problem as they may outlast coils and about 100.000 miles with little problem. A word of warning with these with a 3 valve later engine - make sure that the installer has the right tools including a broken plug extraction tool and follows Ford's Technical Service Bulletin TSB 08-7-6 and if he breaks a plug, uses the Lisle tool LIS65600. Make sure the mechanic is very careful. uses enough solvent to soften any carbon buildup and pull those plugs an 1/8 or less of a turn each time he applies solvent. The plugs will squeak and squeal. Also, once the plugs are out, the engine must be cranked over, blowing that solvent out of the cylinders as hydraulic lock will destroy an engine. The plugs go back in using a nickel based antisieze, making sure it's only on the threads. Oh and yes, I've been there with a now long gone Ford V10.

Next - and if the engine is a 2 valve, you still need to use caution as these, depending on the cylinder head part number used, may tend to tear plug threads if not carefully removed, also using solvent and a partial turn at a time.

Another item to consider is the throttle position sensor. I've replaced these on almost every Ford I've owned since 1986 - including pickups and autos, This shows up as an intermittent miss, 1500-2000 rpm. You F53 probably has a 'drive by wire' throttle operation but there still will be a feed back control device.

Sorry about the cautionary information. The V10 is a great engine, but does need some TLC when it comes time to work on the plugs

Good luck

[TeJay]

IC2,

His engine is a 3-valve. The 3-valve engine came out either late 2005 or early 2006. There should b no question as to the number of valves.

The plug issue isn't that big of a deal. There were more problems with the early 2 valve engine than the 3-valve. In fact I believe what ever was the original issue was change when the 3 valve came out.

The torque on those plugs is in the 23 lb range. So error on the side of caution with the torque. The head is still aluminum so make sure they don't over torque them if and when you get plugs.

Some have said that it may not be the plugs because they are supposed to last into the 100,000 mile range. That may be true but one should still never ASSUME anything. My bet is still on a defective coil and that's where I'd start.

If you get some plugs then go ahead and change them. It's won't hurt anything.

When trying to access a defective coil remember that the engine has to be under load. You can't just disconnect the 12 volt wires going to a coil and rev the engine without it being in gear and under load. When the engine is under load the voltage requirement goes up and that's exactly why the coil fails under load and not at an idle or reeving it up without the load.

When you rev the engine not under load (in gear) the coil voltage output does not change much at all. When the coil is under load the conditions inside the combustion chamber get much harsher (higher compression) and therefore more difficult to jump the spark plug gap. The voltage increases to compensate for the higher reesistance to current flow and the coil insulation intermittently fails.

[ELVIS TOUR]

Once again thank you so much for your excellent replies. It helps so much to not feel alone with this problem.
Food for thought, ours is a2007 so should be the 3 valve. It sounds scary doing the plugs without all the proper gear.
Presumably the COP tester OTC6589 should highlight a faulty coil regardless of engine load? The info about the engine loading and pulling the connectors is very interesting as it explains why we can't detect a difference in the running.
Thanks for the special tool and service manual numbers it gives us more info to look up and prepare with.
The new coils we have now came with new boots and springs attached so they should be good to go.
We had thought we could go through the task of changing each coil in sequence and then start the engine each time and log any differences but have decided to wait for the tester.
One last thing, we think we probably are a drive by wire throttle so where would I find the Control device, I have looked at some V10 schematic diagrams but can't see it but they are pretty unclear. With a bit of luck it has a big arrow on it and a sign. Are there any part numbers for it?
Once again can't thank you all enough for all your assistance.
Hilary

[IC2]

Originally Posted by ELVIS TOUR

Once again thank you so much for your excellent replies. It helps so much to not feel alone with this problem.
Food for thought, ours is a2007 so should be the 3 valve. It sounds scary doing the plugs without all the proper gear.
Presumably the COP tester OTC6589 should highlight a faulty coil regardless of engine load? The info about the engine loading and pulling the connectors is very interesting as it explains why we can't detect a difference in the running.
Thanks for the special tool and service manual numbers it gives us more info to look up and prepare with.
The new coils we have now came with new boots and springs attached so they should be good to go.
We had thought we could go through the task of changing each coil in sequence and then start the engine each time and log any differences but have decided to wait for the tester.
One last thing, we think we probably are a drive by wire throttle so where would I find the Control device, I have looked at some V10 schematic diagrams but can't see it but they are pretty unclear. With a bit of luck it has a big arrow on it and a sign. Are there any part numbers for it?
Once again can't thank you all enough for all your assistance.
Hilary

Assuming tyhat this is a 2007, this is what a TPS looks like. It could be mounted in the air inlet tube or, most likely, on the throttle body . A real good place for identifying parts is Rock Auto RockAuto

Changing spark plugs on a 3 valve V10 can be a scary project if you have never done it before plus can be quite expensive. Unless you break a plug, no special tools are needed except a common to the USA thin wall 9/16" deep 3/8" drive socket

[ELVIS TOUR]

Brilliant, Thanks again to everyone. Will see if I can find that in the morning just so I know where it is. Just in case.
Hils

[c92vette]

Here's a couple of pics as an example to the misfire issue very similar to what I had. The problem may not be as obvious as it is in these photos but given the spark plug in the picture showed such a large amount of corrosion around the shell or area where the socket goes for installation or removal it was real easy to identify the source of the issue. Look carefully at the picture of the plug and note the fine black line running across the white insulator ribs from the terminal towards the shell. That's a carbon trace due to the plug being cracked along that line. Notice the black soot fan spray right above the shell on the insulator. This is where the electric pulse from the coil was arcing to ground causing the misfire under load.




The coil boot in this picture was cleaned thoroughly and reinstalled to a new spark plug and has been going steadily for 20,000 kilometers.



I wouldn't be surprised if this proved to be the problem and I wouldn't be surprised if it was something else. Spark plus are around $7 USD each and coils average $45 USD here in the states. Basic economics at this point suggest replacing all of the plugs, about the cost of the 2 new coils in hand, would be the better path to proceed with. Since you have the coil tester and plan on removing the coils anyway, which you have to do in order to change the plugs, I would spring for a new set of plugs and replace them as well.

[Skip3370]

To reset the engine management light, disconnect the Positive cable on the chassis battery, wait 20 seconds, reconnect. This should clear any faults.

[TeJay]

Carbon tracks are exactly what happens. For what ever the reason the plug gap becomes to great a resistance to jump and/or the current finds an easier path to ground. The end result is a misfire and carbon tracking is the visible result. Uesd to see it very often years ago.

That is also the precise reason the industry has worked very hard to reduce the number of parts that were required to carry and contain that high voltage energy.

We no longer have plug wires, coils wires, distributor caps or rotors. Nothing to break down except the insulation around and within the coils required to contain the secondary voltage and the weak links in the spark plugs.

If an aircraft spark plug is accidentally dropped it is not supposed to be used. They are not cheap either. The insulator can or might be cracked and it can't be seen until carbon tracks expose its location. No need to go into the details why??

[ELVIS TOUR]

Thank you all for the replies they are incredibly useful. When we go quiet with our posting it is only because we are trying to assimilate the information.

We have sent for an OBD reader which should arrive with the coil tester.

We tried changing a second coil but again this has proved inconclusive and was only on a say so that it was the most likely one to have failed.

We do not have sufficient tools with us, and the French mechanics appear reluctant or maybe do not have tools themselves to tackle the spark plugs.

We have also heard that the same symptoms can be caused by a vacuum leak. It would be interesting to hear your faults on this.

Once again thank you all for your valuable assistance and support.

Hilary

[TeJay]

Vacuum leaks will cause other symptoms. First of all lets look at where they might occur.

A cracked or loose vacuum hose can be a source. A warped intake manifold gasket or other gaskets associated with the intake can result in vacuum leaks.

I very often could locate vacuum leaks simply by spraying carburetor cleaner in and around the intake as the engine was running. If it sucked the spray in past a gasket leak of some sort the engine RPM's would change.

Symptoms! Usually a leaning of the intake fuel mixture will result and then an oxygen sensor lean code will appear. A lean air mixture will run hotter. That may result in a misfire but there will also have to be codes as well.

Another thing that happens is the idle speed will increase. Anytime the mixture leans it will cause an increase in engine RPM's. Yes sometimes a misfire will result but you also have to have some of the other symptoms already mentioned
associated with it.

I'm shocked that you can't find a technician who understands what is going on. My radio controlled model airplane engine (60 years ago) would always increase in RPM's as it was running out of fuel (leaning air/fuel mixture).

They have to have some of this technology in France or maybe not. Besides some of what I've explained happened back when we still had carburetors so it's not necessarily new technology.

I know some of what is happening with the computer controls that are trying to correct for a lean mixture but since I retired 11 years ago there's still much of the new technology that I don't know.

Best of luck and thanks for keeping us appraised as to your progress. It's got to be terribly frustrating.

[ELVIS TOUR]

Yes it is frustrating , however we are learning a lot and do not feel so alone being part of this very friendly forum.

Hopefully the OBD tester will arrive in the next few days, as we have now opted for a fast track delivery from England. It will arrive before the coil tester but hopefully will give us a heads up on the problem. We could not opt for a faster delivery on the coil tester.

It is very useful information on the vacuum leak. We will hold off on that until the OBD arrives and we can pick some codes up.

The Spanish campsite is being very understanding about our non arrival for the moment so the pressure is off there.

France, we have found, is always frustrating. Spain is very can do. We changed 5 tyres (after one blew out) in Spain last year and fixed a Smart Car with no dramas and much joviality.

C'est la vie.

Hilary

[THenne1713]

I have read that the PCV hose on the V10 is prone to cracking and giving lean/ air leaks; PCV located in top of a valve cover, but I would also check all rubber hoses on top of engine where the heat gets to them.

[spyderRV]

I had a split hose on the vacuum reservoir which is in the passenger wheel well. I had a lean long term fuel trim.

[ELVIS TOUR]

Thanks to everyone. We did use all the info - checking various bits and pieces while waiting for equipment. We finally got the OBD scanner today, after a six day wait. The scanner showed 9 hard codes and ten pending codes. As we had removed all ten coil connections in an effort to locate the misfire, it was logical that the error which was shown only on the pending list was the offending pot. We have changed the coil on pot ten and although this didn't seem to change much at idle, during a ten mile drive we it didn't appear to miss.

Tomorrow we are putting our money where our mouth is and heading south towards Spain. We have about 600 miles to go. While we are on the road we will not be able to post (next two - three days), but will let you all know if we make it unscathed and misfire free, or if we have to return to safe haven.

Thanks again so much!!!!

Hilary