Injector Harness/failed FICM w/good voltage- what was your symptoms??

[cRaZy8]

Ive exhausted all my possible thoughts about this scenario.

Truck runs well 99% of the time. When it doesnt, it has the SLIGHTEST misfire. Its very hard to hear/feel it. Ive had three different friends (all of which are gearheads) listen to the truck, from inside the cab while driving, and from outside the cab. None of them hear the miss. Either I am going crazy, or its so slight when it happens, no one but myself can hear it (because I drive it everyday?).

Cold starts are good, but not great. FICM stays above 47.5V, but if its below 20*, and the truck isnt plugged in, it romps for 2-3 seconds.

I mostly get the miss when the truck is warm, 20-30 min of continuous driving. It almost feels like a slight shudder.

It has tons of power, even when I feel the slight miss, if I roll into the throttle, it is either so slight I can no longer feel it, or it goes away.

Only other symptom, when the truck is warm, on the highway, in top gear, on part throttle acceleration, it will surge/buck/miss. Fuel pressure is steady at 62-65psi.

I just ordered a harness, fingers crossed this fixes it ( I HATE throwing parts at something to fix it, much rather troubleshoot and FIND the problem).
I have a strong feeling if a new harness doesnt fix the issue.

My only other thought is the FICM has some other issues going on. I doubt that the only time an FICM fails is when the power supply starts to crap out. Maybe when it gets warm, something is breaking a connection?

FICM never drops below 47.5V (FICM was replaced about 2 yrs ago).
8 new injectors 3 weeks ago.
New frame mounted fuel pump with new injectors.
New engine side fuel filter.
Fresh T5 oil.
New turbo this past spring, when Ford replaced the headgaskets (failed BO).
No EGR systems.
Never pukes coolant.
Never loses coolant.
I run RevX every other oil change, and Power Service Cetane boost every fill up.
I push it into high boost almost everyday, for at least a 2-300yd sprint.

One of the reasons I recently thought why I have a damaged harness; this engine has been torn down to the bare block for head gaskets twice, once in cab, once cab off. And when I did the injectors 3 weeks ago, I obviously had my hands all over the harness. I am thinking the harness could have a chafed/broken wire. I see a lot of wiring harness issues at work with Yamaha outboards. Mostly due to improper routing/securing by previous techs/DIY'ers. Thats why I dont want to rule this out on my behalf.


Somebody, anybody, ideas? Input?

I love this truck, but its drives me nuts sometimes. See sig for my mods.

Thanks guys.

[ronnie32567]

my truck is doing the same thing except the miss is bad buck,jumping while cruising at neutral throttle. My wires,ficm and 3 injectors went out at 160,000 engine had a miss but absolutly no power in high gear at cruising rpm 1600-1800 or so if rpm was held at 2000 or above was ok but you could not keep rpm that high with out speeding on most roads. read my post on 6.0 engine miss i just opened today

[ronnie32567]

like you I love my truck 195,000 mi but it is something wrong all the time, think I'll try a cummins they run forever. good luck with your truck

[cRaZy8]

Thanks man. Mine still has plenty of power, and your issue seems a little more severe.


Any techs see this issue before? Anybody??

[bismic]

FICMS fail frequently without having low voltages. The only real way we have to troubleshoot is to swap out w/ a known good one. However, I have heard that you can heat the FICM case for a few minutes / a hair dryer (not a heat gun because that has too much heat capability) and if that helps, you know you have FICM issues. Haven't tried that though.

I have a good FICM and still sent it off to FICMrepair.com. Ed upgrades some components for greater reliability. That was well worth the money to me.

[Dave At BD Power]

New injectors from Ford or remans? I am not a lubrication expert but have had mixed reviews on Rev X.

With what I read, I think your harness are worth changing at this point, have you tried moving the harness to attempt to create a hesitation or even cause a stall?

Dave
BC Diesel

[cRaZy8]

These were remans from Performance Machine Mfg.

I have tried to just wiggle on the harness where it plugs into the injectors, but that doesnt seem to affect anything.

But after looking at the updated harness for the injectors (new style has hard plastic covers directly underneath the FICM harness plugs), I have the old style.
I ordered a new harness yesterday from Tousley. Should have it by tuesday.

I am hoping the new harness fixes it. And I am really holding off on buying a new FICM until BPD has their new unit on the market.

From what I read about harness failures, a chafed waire that has shorted to ground on the block will shut the engine down. Similar to shorting an ignition coil in a gas engine. I would have to imagine that not all four (I think their are four?) wires that go to each injector are not carrying supply voltage. One of them has to be for reference, right? The FICM is taking information back from them, not just supplying info and power, correct? A partially broken wire on a reference voltage feed can play hell with a computer.

We had an issue a couple years ago with Yamaha outboards- the water pressure sensors would fail internally, forcing cooling water pressure through the wire harness (SALT water!). This would make engines do some of the craziest things I have ever seen. Bucking stalling, smoking, backfiring, lopey idle. And it was always the worst when the 5V reference wires became contaminated.

Am I way out in left field with my thoughts?

[Dave At BD Power]

Not at all you are on the right track for what I would be doing... you have done your homework!

keep me posted on the harnesses

Dave

bcdiesel.ca

[bismic]

The ficm has 4 injector driver circuits in it. Those 4 drivers drive 8 injectors.

Driver 1 controls : 1,7
Driver 2 controls : 3,5
Driver 3 controls : 2,8
Driver 4 controls : 4,6

If the drivers are dead the ficm may still show 48volts and still be bad, and this is one of several other failure mechaniusms like that.

Try heating the FICM as suggested and see what it does.

I hope the injectors are not bad. This is one area where the Ford remans are well worth the money. No other company goes over ALL of the parts like Ford does (no matter what they tell you). Lots of unfortunate lessons learned on aftermarket injectors!

[sinner6.0L]

It could still be a wiring concern. The 4 wires going to the injector are in control of two 48v 20 amp soleniods on each side of the spool valve. There is an open and a close solenoid. The spool has no return spring so after a coil pulls it open and de-energizes the spool will remain where it is until the other coil pulls it closed.

The first thing I always look at are the plugs on the bottom of the ficm, especially after a repair that removes it. You're already putting a new harness in, you may find a plug that has no locking tabs on it.

If the harness doesn't fix it you are going to have to isolate the cylinder. Unfortunately I haven't heard one good story about aftermarket fuel injectors. Ford remans for the most part are pretty good.