Ashamed to say I can't quite "feel" which it is. No codes. I've had this for so long once in a while I feel like trying again. It sometimes happens just at normal level cruise speed. Most often I feel it when I just about start an incline but don't give it more pedal.
69k miles. pan was dropped and tq drained with new filter around 65k thinking that was it. Fuel filter is not original. new fuel pump. removed and cleaned out AIC. Battery and alternator are new. Haven't done anything else I can think of. This happened a few years ago and it was a bad cop. With no codes it's hard to find a problem.
Ideas?

 

A Coil problem ?

Taking off normally, - under NORMAL acceleration, at around 45mph, just after the shift into OVERdrive, -how does it run at this particular load. Right after the shift, very important. It could be 50 mph depending on the tune.

It's at this EXACT engine load a coil will act up. So if you have a low grade misfire or any coil problem what so ever, it's at this point in shift/load where it will be at it's worst.

That is how you can cut to the chase, if it's a coil.

 

Thanks.
Last time it was a coil as I mentioned. even told me which cylinder. I'll test your theory but if it is a cop, why no code?

 

Yea consider yourself lucky to get a code (DTC). Usually you end up with no more than a low grade misfire and you won't get one. The misfire monitor needs to count that miss a certain amount of times before it records the correct cylinder.

BUT, if you get a blinking CEL then it turns off, -it has recorded it the cylinder. You DON'T need a CEL to have a DTC on the KAM. That means a scan COULD come up with it.

Yea, your lucky to get a solid CEL. The only time that happens with a coil is when you have a dead hole.

DTC - Diagnostic Trouble Code
KAM - Keep Alive Memory
CEL - Check Engine Light

 

jbrew is correct, it's a coil with low output and is not a hard fault to cause a code.
The reason gets a bit long to explain.
You either have to chase it from cylinder to cylinder with a known good coil or get a dealer stress test done on all of them to pick out which one it is.
Good luck.

 

I'd just replace them all. If you find the one thats missfiring, soon you'll be tracking down another then another until youve replaced them all. Go on e-bay theres the vistian or what ever coils that are motorcraft replacements they say. Get the closest thing to the stock coils you can without killing your finances..

 

I had this happen to me a year or so ago. After messing around trying to get a code thrown I took it to a local shop and had them do real time diagnostics. I let them drive it around with a computer hooked to it that showed what the engine was actuallly doing. It wasnt cheap but it worked. Later that day i had it up and running like new. Oh and i never had A CEL.

 

Yea, that's part of the explanation Bluegrass is referring to I expect. It's call Mode 6 for cylinder history. Or a coil stress test. The Rotunda kit I believe.

That's all high end diagnostic equipment and will usually run you an hours worth of labor @ the D-ship. Plus the part if applicable.

 

For what you are going to pay at the dealership for a stress test and ONE coil, you can buy a full set of Visteons on Ebay.

http://www.ebay.com/itm/New-Visteon-...2fa4a1&vxp=mtr

 

I think we have a winner. Leaving my house, I have a known spot where it happens. Just hit 45, just hit OD and just the start of an incline. And there's the stumble. The downshift made it go away. Then I purposely tried to recreate that scenario. Sometimes yes, sometimes no. And once as slow as 35mph just starting an incline, but def in OD.
I think I'll try the one coil I last replaced first. It was a cheap aftermarket but lasted years. Maybe I'll get lucky.

Thanks Jbrew and all.
Will report back.

 

Wanted to report back. I picked up one new coil and moved it around. I got lucky. found the culprit on the 6th try. Hey, could have been worse, could have been the last one right? lol
thanks to all once again.

 

Just a little more on why it acts the way it does.
During OD and light throttle, the EGR opens and leans the A/F ratio above 20 to 1 which is very lean.
These conditions require the most coil voltage the coils can deliver (or their reserve voltage).
If one coil has shorted turns, it's max voltage is reduced bringing about a missfire.
When you cause a change in engine RPM or a down shift occurs, the A/F goes richer requiring less coil voltage so the problem goes away until the next time the same driving conditions exist.
On top of all this, the coil can be heat sensitive.
As well, the coil issue can prevoke other secondary responses such as interfering noise back into the PCM that can actually shut down processing until the issue goes away.
This shows up as though you switched the igniton off and back on completely killing everything for an instant and causing a violent jerking until the PCM picks up processing again.
In rare instances if the coil shorts such that a very low resistance is present to many times, it can actually burn the PCM coil switch causing the need for a PCM replacment and the cost associated with it.
Good luck.

 

This is an interesting and timely thread, I just finished my 1998 4.6 to 5.4 swap and it runs great...... Except under the exact conditions mentioned above. Under level ground no load situation I think I feel a slight hiccup. I also was trying to decide if it was a transmission glitch or a slight miss. It is so slight I sometimes wonder if I am imagining it. I am running the original 4.6 coil packs not cop. Stick you're foot in it, and it pulls strong and it idles like a rock. Do the coil packs break down and act like the cops? Also I haven't gotten the computer tuned to the 5.4 yet.
Mike

 

It could very well be but on a swap like yours you will have to chase it from that point of view.
I would think your EGR, on a swap, is now out of calibration for the amount of exhaust gas allowed to flow back into the intake when EGR is opened.
If the A/F goes leaner than the coils can handle you could get into the same conditions.
First replace the coils or replace with after market coils known to output higher voltage.
If either clears the problem even on a temporary basis your onto the cause.
Worn plugs will also have an effect as they contribute to the ease of firing the mixture.
Plug tip and ground strap errosion requires more voltage to begin the gap breakdown process to produce the flame kernal that starts combustion..
You might even try to restrict the feedback flow some amount to see if it has an effect then decide on the action to take but be awhere that doing this too much could cause an EGR test failure code of 401 a low flow failure, then you know it is restricted to much..
Report on what happens.
Good luck.

 

Thanks for the reply, a little history. The engine is a 2004 2v 5.4 unmolested new factory crate motor for an Expedition. It has all emissions and sensors that came with the engine plus the 2 additional heat sensors from the 4.6, I put in new plugs since I removed the originals to squirt a little oil in the cylinders since it has sat for years. I used a 2000 5.4 fuel rail and injectors because it had the newer style injector and the fuel rail had no return. I'll probably try replacing the coil packs since everything else is new and I need to get a tune. The truck runs like a beast and I'm very happy.
Mike