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Rough idle on the 6.0

Old Feb 15, 2024 | 10:32 AM
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Originally Posted by CathedralCub
They'll lean out if there is way too much fuel pressure. Not sure if that'* what is happening here, but it'* a possibility.
If that'* the case it should code.If that is a correct reading it '* taking away 60%.
I do not believe the IPW numbers are correct.

Last edited by carfixer007; Feb 15, 2024 at 10:34 AM.
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Old Feb 15, 2024 | 10:49 AM
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even on bigger port injected engines the highest i see at IDLE is 3.5, this 6.0 idles pretty low at like 580rpm so not sure, that beign said ipw does fluctuate when driving, idle is around 1.4-1.8ms, driving is like 3-5ms under gentle accel. MAF is reading 5.98g-6.1g at idle, map sensor is around 4.9psi at idle. The only thing other that is off to me is that under accel it likes to jump the ign timing to like 35-40 and around 50 when going 40mph
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Old Feb 15, 2024 | 04:29 PM
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*UPDATE*

It is now down to 1.2ms at idle, it is like 50 degrees out and when fully warm, this is the data when sitting at idle, coolant temps and oil temps at operating temperature respectively.

RPM: 570
MAF: 5.2-5.4g
Throttle actual angle: 3%
MAP: 4.4psi
IPW (bank 1 and 2): 1.2ms

LTFT bank 1: +- 0
LTFT bank 2: +2





WHEN COLD, THE FIRST ACCEL like i said it was stumbling:

the vvt camshaft commanded position is 35
the actual position is 5-10

not sure if that helps with diag but this has me pretty stumped^
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Old Feb 15, 2024 | 06:26 PM
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Originally Posted by TopLock
*UPDATE*

It is now down to 1.2ms at idle, it is like 50 degrees out and when fully warm, this is the data when sitting at idle, coolant temps and oil temps at operating temperature respectively.

RPM: 570
MAF: 5.2-5.4g
Throttle actual angle: 3%
MAP: 4.4psi
IPW (bank 1 and 2): 1.2ms

LTFT bank 1: +- 0
LTFT bank 2: +2





WHEN COLD, THE FIRST ACCEL like i said it was stumbling:

the vvt camshaft commanded position is 35
the actual position is 5-10
not sure if that helps with diag but this has me pretty stumped^
Those trims show near perfect fuel control. Your numbers puzzle me.
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Old Feb 15, 2024 | 06:45 PM
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same... I am very confused. Also I looked back at my data and the vvt thing is perfectly fine, command was at 10 and so was output. So maybe this thing is like some chevy v8'* and it just runs a tad rough at idle? But ya ltft is perfect bank 1 and just a bit of fuel added on bank 2... not sure why my pw is at 1.2 tho. These are 42lb/hr injectors which are larger than usual so maybe they are flowing more fuel and can stay lower? I know some guys run as low as 0.4ms on 48lb injectors
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Old Feb 15, 2024 | 11:10 PM
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Factory stock is 42.9lb/hr so those should be fine.

I can't remember if we've gone over this: What is the air filter like? Clean/dirty/K&N/etc. ?
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Old Feb 16, 2024 | 12:16 AM
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Sorry I meant to say 42/hr not 48.

Air filter is 5k miles old, looks brand new with almost no particles in it. I have yet to test fuel pressure but if trims are near perfect idk why its still idling slightly rough OR having this little hiccup on the first accel, its very light but its a definitive cut if ur lightly accelerating the first time it cuts 2 or 3x every time at the same point. The other thing I have noticed is if the engine was warm, I shut it off and go about my business, and come back and start it still warm but coolant temps have dropped, the first actual accel where I am getting up to 2000rpm, the 1-2 shift the revs surge right before the shift. Not a whole lot just a tiny noticeable surge only under that exact condition. I let my motor warm up from cold for like 2-3 minutes, idk if maybe an injector is leaking and causing that or maybe it is fuel pressure. I just really like sitting with an engine at idle that has no roughness to it
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Old Feb 16, 2024 | 07:06 PM
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if my fuel pressure is low or high wouldnt the trims reflect it?
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Old Feb 16, 2024 | 09:43 PM
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Originally Posted by TopLock
if my fuel pressure is low or high wouldnt the trims reflect it?
The PCM has a map of 'tolerance' which allows for some change and still keep fuel control. If the pressure of another parameter like say the MAF gets to far out of whack it can't control the fuel it will set the appropriate code.
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Old Feb 17, 2024 | 12:03 AM
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so do you think its good then? I work on german vehicles and this just stuck out to me, idk i have heard these big ohv chevy v8'* just run a bit rough, possibly internal secondary balance/ running lean on purpose (higher map afr) to meet emissions?
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