06 5.4 help
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5th Wheeling
Joined: Sep 2017
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06 5.4 help
Ok still working on my mom's truck, I have found when hot and you just blip the throttle or just give it steady slight throttle it starts running very rough. Fuel trim goes +40 bank 1 -20 bank 2. Rev it up a few times engine smooths out but kinda rough. Fuel trim bank 1 -8 bank 2 +3. Smoked intake found no leaks. Vacuum at intake at idle 18invac. 20 invac under load. Any thoughts. Gonna bring fuel guage home tommarow and check fuel pressure. Any ideas on what else to check
Posting Guru
Joined: Jan 2015
Posts: 1,083
Likes: 33
From: San Antonio, Texas
@moneymike your symptoms are 'CLASSIC' timing symptoms resulting from Phasers that cannot HOLD cams at proper position on supplied Oil Pressure at the given RPM.. Translating them into specific mechanical (or rather hydraulic) causes is a little bit tedious. Generally speaking: The Phasers have a spring loaded locking pin internal that captures and locks the Phaser into base (zero retard) as the engine idles down from RPMs that produce enough oil pressure to assure Phaser can push cam to Zero Retard.
As long as engine idles and oil pressure is insufficient to UNLOCK the spring loaded locking pin - the phaser stays locked in full advance position --- even if Oil pressure is insufficient to do the job.
What you describe -- "give it slight acceleration", as RPM rises so does oil pressure. Once the Locking pin dis-engages (it is spring loaded), then the oil pressure MUST be sufficient to take over and hold Phaser at 'proper' position (whatever the PCM is requesting) - which is still ZERO degrees retard below about 800 to 1000 RPM "AND" below 25% engine load.
Your 'rough running' is classic symptom of the two banks cam timing NOT being balanced. A retarded cam does NOT aspirate as much air - so the cylinders on that bank are "WEAK". That condition is 'CONFIRMED' by your inbalanced Fuel Trims. Less air being drawn in makes fuel mixture WRONG for that bank and the PCM sees it at the O2 sensor and attempts to compensate. The oposite bank works harder trying to help the lazy side and drives its fuel trims the opposite direction. The CAMS are not synchronized equally with the crankshaft.
WHY. Probably a tensioner blown degrading oil pressure in one head - or possibly more serious oil pressure loss in one head or Phaser vanes.
Sorry for the bad news.
As long as engine idles and oil pressure is insufficient to UNLOCK the spring loaded locking pin - the phaser stays locked in full advance position --- even if Oil pressure is insufficient to do the job.
What you describe -- "give it slight acceleration", as RPM rises so does oil pressure. Once the Locking pin dis-engages (it is spring loaded), then the oil pressure MUST be sufficient to take over and hold Phaser at 'proper' position (whatever the PCM is requesting) - which is still ZERO degrees retard below about 800 to 1000 RPM "AND" below 25% engine load.
Your 'rough running' is classic symptom of the two banks cam timing NOT being balanced. A retarded cam does NOT aspirate as much air - so the cylinders on that bank are "WEAK". That condition is 'CONFIRMED' by your inbalanced Fuel Trims. Less air being drawn in makes fuel mixture WRONG for that bank and the PCM sees it at the O2 sensor and attempts to compensate. The oposite bank works harder trying to help the lazy side and drives its fuel trims the opposite direction. The CAMS are not synchronized equally with the crankshaft.
WHY. Probably a tensioner blown degrading oil pressure in one head - or possibly more serious oil pressure loss in one head or Phaser vanes.
Sorry for the bad news.
5th Wheeling
Joined: Sep 2020
Posts: 44
Likes: 0
VCT Solenoid
@moneymike your symptoms are 'CLASSIC' timing symptoms resulting from Phasers that cannot HOLD cams at proper position on supplied Oil Pressure at the given RPM.. Translating them into specific mechanical (or rather hydraulic) causes is a little bit tedious. Generally speaking: The Phasers have a spring loaded locking pin internal that captures and locks the Phaser into base (zero retard) as the engine idles down from RPMs that produce enough oil pressure to assure Phaser can push cam to Zero Retard.
As long as engine idles and oil pressure is insufficient to UNLOCK the spring loaded locking pin - the phaser stays locked in full advance position --- even if Oil pressure is insufficient to do the job.
What you describe -- "give it slight acceleration", as RPM rises so does oil pressure. Once the Locking pin dis-engages (it is spring loaded), then the oil pressure MUST be sufficient to take over and hold Phaser at 'proper' position (whatever the PCM is requesting) - which is still ZERO degrees retard below about 800 to 1000 RPM "AND" below 25% engine load.
Your 'rough running' is classic symptom of the two banks cam timing NOT being balanced. A retarded cam does NOT aspirate as much air - so the cylinders on that bank are "WEAK". That condition is 'CONFIRMED' by your inbalanced Fuel Trims. Less air being drawn in makes fuel mixture WRONG for that bank and the PCM sees it at the O2 sensor and attempts to compensate. The oposite bank works harder trying to help the lazy side and drives its fuel trims the opposite direction. The CAMS are not synchronized equally with the crankshaft.
WHY. Probably a tensioner blown degrading oil pressure in one head - or possibly more serious oil pressure loss in one head or Phaser vanes.
Sorry for the bad news.
As long as engine idles and oil pressure is insufficient to UNLOCK the spring loaded locking pin - the phaser stays locked in full advance position --- even if Oil pressure is insufficient to do the job.
What you describe -- "give it slight acceleration", as RPM rises so does oil pressure. Once the Locking pin dis-engages (it is spring loaded), then the oil pressure MUST be sufficient to take over and hold Phaser at 'proper' position (whatever the PCM is requesting) - which is still ZERO degrees retard below about 800 to 1000 RPM "AND" below 25% engine load.
Your 'rough running' is classic symptom of the two banks cam timing NOT being balanced. A retarded cam does NOT aspirate as much air - so the cylinders on that bank are "WEAK". That condition is 'CONFIRMED' by your inbalanced Fuel Trims. Less air being drawn in makes fuel mixture WRONG for that bank and the PCM sees it at the O2 sensor and attempts to compensate. The oposite bank works harder trying to help the lazy side and drives its fuel trims the opposite direction. The CAMS are not synchronized equally with the crankshaft.
WHY. Probably a tensioner blown degrading oil pressure in one head - or possibly more serious oil pressure loss in one head or Phaser vanes.
Sorry for the bad news.
Posting Guru
Joined: Jan 2015
Posts: 1,083
Likes: 33
From: San Antonio, Texas
You're right. That's what is hard about diagnosing our phaser system. About anything in the system can cause similar symptoms. It would be possible for the screen on a VCT solenoid to break or clog or something to limit oil flow/pressure from getting to the Phaser effectively.
Yes, the little locking piin (about the size of a pencil) about 1/2 inch long has a spring under it. The spring pushes it up and locks the two halves of the Phaser together. Oil pressure ---- Above a certain pressure ????? --- pushes it down and allows the vanes in the actuator chambers to move the back half (connected to the CAM) with respect to the front half (connected to the gear).
Both banks are controlled INDEPENDENTLY by the PCM in a 'positive feedback', closed loop fashion. Controlling position with VCT solenoid and reading actual position by CPS sensors. (Actually amazing it works as well as it does).
Yes, the little locking piin (about the size of a pencil) about 1/2 inch long has a spring under it. The spring pushes it up and locks the two halves of the Phaser together. Oil pressure ---- Above a certain pressure ????? --- pushes it down and allows the vanes in the actuator chambers to move the back half (connected to the CAM) with respect to the front half (connected to the gear).
Both banks are controlled INDEPENDENTLY by the PCM in a 'positive feedback', closed loop fashion. Controlling position with VCT solenoid and reading actual position by CPS sensors. (Actually amazing it works as well as it does).
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