Very intermittent misfire/cam code issue - p0390/p0394

[jack28baker]

Really confusing issue I am having here. Any help is appreciated. After doing pac1234x springs, ops/cs, and new/upgraded timing components, my car has a odd and very intermittent issue where once every couple redlights/stops, it will misfire bad and it goes away right when i get back into rpms. 2 codes for my bank2 sensor 2 cam sensor (drivers side exhaust cam) and during the misfire events, it is usually cylinder 8 and sometimes 5. It will only misfire when coming to a stop, it will not start if i just sit at idle. I re timed entire engine today thinking it was a tooth off and am now a little clueless. Also replaced the cam sensor and that did nothing as well. Getting higher in rpms seems to get rid of the misfires instantly, say It is misfiring at 1k rpm, i will downshift and it will immediately stop. Some drives it will drive great, no issues at all. The drive after it might misfire at the first stop i get to. Everything I changed when doing the valve spring/opg job was all gaskets, opg/cs, pac1234x springs, boss 302 primary tensioners, secondary tensioners, phasers and cam filter, guides, primary/secondary chains, and went from amsoil 5w50 to mobil 1 5w30. I am having trouble thinking it is a mechanical issue due to how random and intermittent it occurs.

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[Timbuck]

Ok. There is a few things I’d look at. Due to its happening at low RPM it could be a stuck solenoid. This can occur if a bit of silicone or crap has got into it and it cannot return to it commanded position as it get back to idle. You could try and swap a solenoids around to see if the problem moves with theat exaust solenoid. Also can you do a data log and see what the cams are doing. It will give you a bass line to work from.
Also. Wires. The wires that go to the solenoids are fragile right where they bend over. Just make sure it all good there.

 

[Timbuck]

Oh. And also make sure it contacting properly as one of mine was bent slightly when I did my engine , and the centre pin wasn’t perfect 90deg

Edit. Video might help.

 

[jack28baker]

Ok. There is a few things I’d look at. Due to its happening at low RPM it could be a stuck solenoid. This can occur if a bit of silicone or crap has got into it and it cannot return to it commanded position as it get back to idle. You could try and swap a solenoids around to see if the problem moves with theat exaust solenoid. Also can you do a data log and see what the cams are doing. It will give you a bass line to work from.
Also. Wires. The wires that go to the solenoids are fragile right where they bend over. Just make sure it all good there.

I replaced both drivers side solenoids a few days ago hoping it would fix it, nothing changed pretty much. I will check the wiring though now.

 

[jack28baker]

*Update* did data-logs and the issue of course didn’t want to occur when i was logging, but looking at both exhaust cam positions, i can say that i can completely rule out timing being off. 30 minutes of driving and average exhaust timing was only .12 off bank 1 from 2.

 

[Timbuck]

Haha Murphy’s law. Never happens when you want it to.

Maybe playing with the wiring did something ??

 

[jack28baker]

Haha Murphy’s law. Never happens when you want it to.

Maybe playing with the wiring did something ??

Definitely a possibility, I’m not not sure 100% where to check and how. Wiring is definitely not my specialty lol

 

[jack28baker]

Was able to log it. When misfires start, all cams appear to drop to 0.07 degrees. Not sure if thats what it defaults to if it looses signal or something.

 

[Timbuck]

To my knowledge, the reading should be very similar within a few degrees. The difference between bank 1 and 2 exhaust is something to look at. Cams will go to zero at idol , start up etc and raise with rpm.

I’ll do a data log on mine today to compare.

@engineermike is the man when is come to this shit.

 

[engineermike]

Ford uses some methodology called FMEM. Basically, they try to think through all the possible failure scenarios and build fail-safe functionality into the logic. When it senses a cam position problem, FMEM sends all cams to "home" or "park" position, which is 0, 0. That's why they do what they do when the MIL comes on. I've found various faults that will cause this, everything from erratic position to too much variation between cams. I don't know how good your tune is, but many tunes aren't that dialed in well at MP0/14 timing 0,0 which may cause misfires.

That said...the P0390 and 394 appear to be position sensor faults, one indicating intermittent and the other being hard fault. It can check for things like phasing out of range, speed of cam exceeds range, or no signal detected and that constitutes and error is counted and accumulates. Accumulate enough and it triggers a code and goes into FMEM.

I might be able to tell more if you log desired exhaust cam position, actual exhaust cam position, and phaser duty cycle. I'd log these and maybe a couple of other parameters at a high data rate to give the best chance of seeing what's going on.

 

[jack28baker]

Ford uses some methodology called FMEM. Basically, they try to think through all the possible failure scenarios and build fail-safe functionality into the logic. When it senses a cam position problem, FMEM sends all cams to "home" or "park" position, which is 0, 0. That's why they do what they do when the MIL comes on. I've found various faults that will cause this, everything from erratic position to too much variation between cams. I don't know how good your tune is, but many tunes aren't that dialed in well at MP0/14 timing 0,0 which may cause misfires.

That said...the P0390 and 394 appear to be position sensor faults, one indicating intermittent and the other being hard fault. It can check for things like phasing out of range, speed of cam exceeds range, or no signal detected and that constitutes and error is counted and accumulates. Accumulate enough and it triggers a code and goes into FMEM.

I might be able to tell more if you log desired exhaust cam position, actual exhaust cam position, and phaser duty cycle. I'd log these and maybe a couple of other parameters at a high data rate to give the best chance of seeing what's going on.

Makes perfect sense, i though they were being put in some sort of fail safe the way all of them reacted in unison. I use sct livelink to datalog and a desired exhaust cam pid doesn’t show up for some reason, but now i am thinking that the phaser for the cam with the codes may be bad/defective, Causing the fail safe. Just a theory for now.

 

[engineermike]

To differentiate, there is a phaser and a phaser solenoid. It's fairly unlikely that the phaser itself could cause these particular error codes unless the cam jumped a tooth (out of range code). This doesn't appear to be a "it's not following commanded" type of code. The good news is that it appears to be pointing more at the phaser solenoid, which is actually pretty easy to replace on these and low cost.

 

[jack28baker]

To differentiate, there is a phaser and a phaser solenoid. It's fairly unlikely that the phaser itself could cause these particular error codes unless the cam jumped a tooth (out of range code). This doesn't appear to be a "it's not following commanded" type of code. The good news is that it appears to be pointing more at the phaser solenoid, which is actually pretty easy to replace on these and low cost.

Already replaced both solenoids on drivers side after issue came up, didn’t change anything

 

[jack28baker]

To differentiate, there is a phaser and a phaser solenoid. It's fairly unlikely that the phaser itself could cause these particular error codes unless the cam jumped a tooth (out of range code). This doesn't appear to be a "it's not following commanded" type of code. The good news is that it appears to be pointing more at the phaser solenoid, which is actually pretty easy to replace on these and low cost.

It is entirely possible that i pulled a wire too hard though, it isn’t easy to take off the Christmas tree pins on the valve cover and i could have damaged something, just odd that it only happens at idle after rolling stop 90% of the time it misfires.

 

[engineermike]

I thought about this a minute and this is actually an error of the cam position sensor, not the phaser. It’s saying the cam positions sensor isn’t getting valid data, either rpm or position out of range or no or intermittent signal.

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