Hi everyone, I am new to the forum, and a contributor to this sites sponsor - 5 Star Tuning.

I know the misfire condition is covered a lot, but my situation is different, so please help me troubleshoot - in brief, I have random misfires and no CEL/MIL, can happen when idling or on a smooth road, but definitely happens sometimes immediately upon hitting a bump in the road.

I have a 2007 E-450 Class C RV with the 6.8 v10 with 45,000 miles.
It has the Bank's headers & exhaust with factory intake and tune all from this site's sponsor - 5 Star Tuning.

I have an Autel scanner that can do Mode 6 and Power Balance test.

After returning from a 6,000mi trip, I hooked up scanner and I had 160 total misfires distributed randomly across all cylinders.
I now use a dash-mounted OBD-II to monitor things like engine temp, trans temp, and "Misfire 1000 Event"
On numerous occasions while driving, the "Misfire 1000 Event" will display a misfire immediately upon hitting a bump on the Interstate at a bridge overpass - not every time, but happens enough to not be coincidental.

My LTFT is 0.39m and my STFT is -1.5 on both banks.

This weekend I replaced the factory installed plugs with Motorcraft SP479 gapped .054
Old plugs all looked consistent and normal.
All COP boots looked very clean and no abnormal signs. Reinstalled COP's with Permatex dielectric grease on tips of boots.
Also, this weekend I replaced the fuel filter with Motorcraft, and a new Fram air filter.
All the COPS are factory original Motorcraft with the exception of an O'Reilley brand on cyl 10 - about 20,000mi ago on a trip I had a CEL/MIL for misfire on cyl 10 and in a pinch I replaced it with a O'Reilley brand.

The battery is Interstate and brand new.
The ground cable from battery to body is clean and tight.
The ground cable at the starter is clean and tight.
The ground cables on the driver side fender by the junction block appears clean and tight.
There are no active or pending codes.
Never had rodent problems on anything around my house - I have looked all over everything meticulously and see no signs of rodent damage.

I am leaning toward bad sensor, poor connection, or bare/broken wire since the misfire has happened numerous times immediately upon hitting a bump on the Interstate.
The camshaft position sensor connection is fully connected and tight.
I have not yet checked the connection at the CKP / crank position sensor, but will do that tonight.

I have seen the "Misfire 1000 Event" appear while sitting still and idling or driving on a smooth road, but it has happened enough times immediately upon hitting a bump on the Interstate to not be coincidental.

After changing the spark plugs, fuel & air filter, I took it on a 35mi test drive - I had 8 misfires - 1 misfire on cyls 2, 3, 4, 5, 7, 9 and 2 misfires on cyl 10.
It is not misfiring enough to trigger a CEL/MIL.

Other than checking the CKP connection, what are the next logical steps for troubleshooting?
Is there something I should be monitoring with the Autel when I go on a test drive and reproduce the misfire when hitting a bump?

Any and all help is appreciated, and once resolved, the solution will be posted!

Thanks everyone!

 

All the COPs have wires going to the PCM where they are grounded, then ungrounded, at the appropriate times to fire the plugs.
Since there are misfires on almost all the cylinders the common points would be the 12v power supply line and the PCM ground.
I would pull the PCM mounting bolts, clean the surfaces and be sure you have a good ground for the PCM.

 

Is the mounting bolts the only ground source?

My PCM has three connectors. Can you tell me which connector has the positive lead and what color it is?

Thanks!

 

I'm looking at our 2002 Excursion Wiring Diagram which is going to be different than yours, but sometimes things don't change a lot.
The drawing shows for the COPs and Fuel Injectors the circuits are grounded inside the PCM.
In the drawings I haven't seen any wires exiting the PCM on a connector to ground so I'm assuming the grounds are thru the PCM case to the vehicle chassis.
Power for the PCM usually is supplied from the PCM Power Relay triggered by the Ignition Switch being in RUN or START.
COP power usually is supplied from the Ignition Switch and the Fuel Injectors from the PCM Power Relay.
It might be possible a bump could affect contacts in a relay.
A poor/loose connector could be jostled by a bump to cause an intermittent open line.

 

I'd suggest you acquire an EVTM for your year, its just an E-Series so this sort of manual would be quite useful to the DIY or anyone doing electrical work: 2007 EVTM

There are also a few more of differing conditions and prices available on eBay using this link: https://www.ebay.com/sch/i.html?_fro...=34219&_sop=10. If that doesn't work simply use the search term "2007 e-series wiring" under the "other car manuals" on eBay Motors.

Hope this helps.

 

Something like this is going to be hard to find, unless you stumble upon it. (pun intended)

With misfires across all cylinders, and the feeling of misfiring when you hit bump, I'm going to say it's either a ground or a +12 supply to the coils/injectors. Fuel pump voltage wouldn't cause an immediate misfire on a bump.

If it were me, I'd be hooking up a two-input oscilloscope to the +12 on a COP and the COP signal from the PCM, and driving around hitting bumps to see if anything happens. Without an oscilloscope, it's gonna be rough.

 

Is factory gap on the plugs .054?
i had misfire on 1 and 5 randomly and swapped coils, plugs and injectors now bank one to rich and mpg went from 8.1 to 9.8.
not complaining but I see gas needle moving south faster.

i think my injectors at 19# are feeding too much or gap on plugs are off. Any input on gap or factory injector spec? 19# correct?