I've got a 1999 E-250 with 88K miles on it. About a month ago the service engine light came on and I went to Autozone where they pulled the code. It said that #3 cyl. was misfiring. So I followed my rule of changing the cheap stuff first I went for Autolight plugs and wires. It ran fine after this but the SEL has come on again and set the same code.

Now my question. Is the coil pack made up of 6 separate coils, And if so would 1 weak coil set this code? This would seem to be the most obvious place to look since it is only one cyl.

Any advice would be greatly appreciated.

 

the coil pack on the 4.2 is all one piece.and it might be causing the code to set

 

I've seen older race cars with crank triggered ignition that used a coil for each cylinder. I was told that at higher RPM it gave the coil more time to become saturated and deliver a consistant spark at all speeds. So when I ask if there is more than one coil. I mean more than one in the same case. Six coils in one box?

 

The 4.2 uses a single coil assembly for all 6 cylinders.

A persistent single cylinder misfire can also be caused by either valve or injector problems besides a secondary ignition system problem.

"Reading" the #3 plug may provide additional clues.

The 5.4 (all years) and the 4.6 (from around 99-on) all use the single coil per cyclinder system, called COP (Coil On Plug).

Steve

 

Soul-tez,
Welcome to FTE! Glad to have you here and I hope we can help you.
Since bothtimes the CEL code indicated cylinder 3, I'd be suspicious of something causing the problem to re-occur.
First thing that comes to mind is a slight leak of coolant into the intake for that cylinder, causing a buildup on the plug and then misfires.
I'd pull the plug and inspect it. Compare it to a plug (or plugs) from different cylinders.
Worth investigating it to rule it out (or confirm it so you can get it fixed).

There have been a few coil pack problems mentioned here over the years, but it does not appear to be a common problem. That said, it does seem to be a legitimate candidate for suspicion in your case.

As mentioned, it could be an injector as well.

Let us know what you find.

 

OK first and easiest thing to try is apply vacuum to the EGR valve while it is idleing. If everything is normal the engine should buck and jerk and may stall. But If the problem is what I think it is the engine will misfire. What happened if it misfires is all the EGR ports in the lower intake except #3 is clogged with carbon and all the EGR gases are goint to #3 cyl causing a lean misfire. To fix it all you have to do is remove the upper intake and clean out the ports with a pick and blow out the soot with compressed air.

 

WOW Thanks for the advice. I'll do some snooping around and let you know what I've come up with.

Mike

 

OK so I did the EGR test (very good thinking by the way) and it did exactly as you said. The engine complained then stalled each time. I did a compression test and checked the resistance of the plug wires.These were fine. So this led me to the ford dealer to buy one or all six injectors. $115.00 each! And they recomend changing all six. So the guys behind the counter talked me into cleaning the injectors. Now I'm skeptical of a quick fix but there was three of them against my better judgement and it was only $97.00. It seems to have worked. The miss is gone and power is back up to where I remember it. I can't help but worry that it's running on a really high percentage of gumout and when this is gone I'll be right where I started.

Thanks for the help. I hope I can return the favor.

Mike