CPAS/rough idle question

[WarGawd]

I was reading another thread a moment ago, didn't want to hijack it with this question. But in that thread roadie posted:

...Dirty throttle bodies and crappy CPAS solenoids are the typical causes of low/erratic idle. I think you have cleaned the throttle body recently, and I don't know the state of your CPAS.

From info I have picked up recently my understanding has become that the cam phaser is not supposed to be operable below 1200rpm...above that the PCM will dial in some amount of exhaust cam retard actuated via engine oil pressure & CPAS, with the CPS closing the feedback loop back to the PCM. What's the connection between bad CPAS and rough idle? Bad CPAS keeps oil pressure applied and exhaust cam stays retarded at idle speeds?

Just curious - I had one or two stall outs in the time after I cleaned my TB, thought it was just relearning, but one of those was more recent and should be well past the time needed for any relearning. May give me something to chew on.....

Thx

 

[Voymom]

This is so far the best "short" answer I have came up with(Googled). I don't know if this answers your question or not.

The Camshaft position actuator solenoid controls the exhaust camshaft retard position. From 0 to 25 degrees. It is driven by a pulsed electrical signal from the ECM... much like that of a fuel injector.
It is located on the front-passenger's side of the motor... on the head. Removal requires the partial removal of the steering pump.
It is prone to failure mainly due to debris in the motor oil that flows into it. An oil change and/or removal of the solenoid actuator to clean of the screens of it can sometimes resolve a related DTC.

I keep reading different things though....so I never know which answer is the right one. I did ask what relevance the CPAS had with my issue, but from what Roadie said and what I have read...seems a bit contridictory(sp). If my CPAS is the issue, that's fine, no biggy. But I have read several times that the CPAS relies on oil pressure to function properly....I had my low oil pressure light trigger during stalls, but no low oil pressure. So if my low oil pressure is due to whatever issue I have going on, how does the CPAS come into play, unless it has to do with keeping the oil pressure up in the vehicle.

I hate google sometimes...I get 50 different answers and never know which one is the correct one.

 

[WarGawd]

Thx Voymom, there's some decent info there about the operation of the CPAS which is essentially part of the same set of info I had learned and was referring to above...but I don't see anything that actually addresses the means by which the CPAS can cause bad/rough idle. That's the part I was hoping roadie would expand on given his answer in your thread

Cheers

 

[Voymom]

Thx Voymom, there's some decent info there about the operation of the CPAS which is essentially part of the same set of info I had learned and was referring to above...but I don't see anything that actually addresses the means by which the CPAS can cause bad/rough idle. That's the part I was hoping roadie would expand on given his answer in your thread

Cheers

That's what I have been looking for too...I don't doubt roadies knowledge and He is absolutely right that my symptoms can be caused by a faulty CPAS(called my trusted local mechanic), but how it causes the symptoms would also be nice to know. Again...google gives me way to many indirect answers, or at least I cannot decipher which answer is correct. Hopefully the roadie can chime in soon and give us both an answer to this question.

I have been trying to cope with this issue, but the stalling in the middle of the road is my breaking point. It leaves me a bit paranoid putting my children in the truck, as I'm terrified it will stall while I'm going through an intersection putting me and the kids at risk for a really bad situation. I'm kicking myself in the ass now for not replacing the CPAS in the beginning.

 

[The_Roadie]

I actually don't know the precise mechanism that the CPAS can be the root cause, I just remember all the posts I've read. About all it can do is disobey a positioning command, so I'd guess internal stickiness resulting in incorrect valve overlap.

 

[Wooluf1952]

I actually don't know the precise mechanism that the CPAS can be the root cause, I just remember all the posts I've read. About all it can do is disobey a positioning command, so I'd guess internal stickiness resulting in incorrect valve overlap.

That would be my guess, too.
That would also explain why using Restore would cause a problem. Or cleaning the CPAS screens and doing an oil change could fix it.

 

[Voymom]

That would also explain why using Restore would cause a problem.

Poor Mat will never live that down

That was a HARD lesson to learn. I think the CPAS is fried in my truck, after the restore and even with cleaning the CPAS my issues never went away. Hoping that replacing the CPAS will fix the issue.

 

[McGMT]

I actually don't know the precise mechanism that the CPAS can be the root cause, I just remember all the posts I've read. About all it can do is disobey a positioning command, so I'd guess internal stickiness resulting in incorrect valve overlap.

Seems to me that it would be even worse after the redesign. The older ones should just stick at the normal position but by my understanding the newer style could get stuck either way causing more evident issues.

 

[The_Roadie]

Poor Mat will never live that down

Replace the CPAS, and then present him with the old one at the wedding reception. His first gift from you will be a constant reminder of what a screwup he is, and how forgiving you are. You can milk that one a long way.