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CAM shaft actuator

Tiny
KEITH DOLPHIN
  • MEMBER
  • 2008 GMC ACADIA
  • 3.6L
  • V6
  • AWD
  • AUTOMATIC
  • 117,000 MILES
My vehicle started running bad sometimes. Let it sit and start it later and it would run good for awhile but start to run like it is running out of gas and rough then stall and not start. Started running bad quicker every time until it only stays running for a few minute's before stalling and will not start. The dealer said it was stretched timing chains. I took the engine out and took it apart enough to see the cam shafts and the actuators. Dual over head cam. I took the plugs out and noticed the driver side plugs were fairly white. I took out the other side and they looked like that side had been running rich or not firing at all (slightly black). I used a socket to turn the engine over. The four actuators and cams would turn, but at a point the driver side intake cam shaft and cam sensor ring would stop turning. The other three cams would keep turning. It would then get to a point were the one that was not turning would start turning fast as if to catch up to were it should have been if it would not have stopped. Is this a problem or are the other three actuators a problem or are they all good and the timing chains need replacing? They seem to work with oil pressure is what I got from one of your articles. Any light you could shed on this would be great.
Keith D
Sprint Guy
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Friday, January 31st, 2014 AT 6:41 PM

20 Replies

Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
Did you scan for codes and check fuel pressure first as well as fuses that supply power to coils and injectors? It could be the actuators. Check to see if everything is in line timing wise it still could be an actuator.
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Saturday, February 1st, 2014 AT 6:42 AM
Tiny
KEITH DOLPHIN
  • MEMBER
  • 5 POSTS
I did scan for codes. Multiple misfires. The dealer also check the codes and said timing chain is stretched. Am I suppose to doubt the dealer ships mechanic about what is wrong? I have an OBD2 scanner and the codes that came up besides the misfires were all related to timing chain trouble. So you do not know how the actuator is suppose to work when the engine is cranked over by hand? Another shop looked at it after I gave up and they checked a lot of things and said I need to take it to the dealer even though they do not like dealerships. I need to find someone who knows about how actuators work. I will post and let you know what happened after I find out.
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Saturday, February 1st, 2014 AT 6:52 PM
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
Cam actuators are electrically operated from the PCM the PCM tells the actuator whether to advance or retard depending on rpm and TPS as well as other sensors. It retards at idle then advances as rpm's go up in order to get more power form the engine. Misfires can be caused by any sensor as well as injector/plug/wiring/coil problems as well as any other engine problem like low compression etc. Dealer mechanics can be wrong as well as anyone else as they are not infallible. If you have the auto parts scanner it cannot do what a pro style one can. At no time should an actuator be activated due to a blade inside will mess up and the actuator will have to be replaced. Your problem could very well be the chain stretch as well as at lest the one actuator. Enclosed is the actual actuator description and operation.
Camshaft Position (CMP) Actuator System
The camshaft position (CMP) actuator system is an electro-hydraulic operated device used for a variety of engine performance and operational enhancements. These enhancements include lower emission output through exhaust gas dilution of the intake charge in the combustion chamber, a broader engine torque range, and improved fuel economy. The CMP actuator system accomplishes this by changing the angle or timing of the camshaft relative to the crankshaft position. The CMP actuator simply allows earlier or later intake and exhaust valve opening during the four stroke engine cycle. The CMP actuator cannot vary the duration of valve opening, or the valve lift.
During engine off, engine idling conditions, and engine shutdown, the camshaft actuator is held in the park position. Internal to the CMP actuator assembly is a return spring and a locking pin. During non-phasing modes of the camshaft, the return spring rotates the camshaft back to the park position, and the locking pin retains the CMP actuator sprocket to the camshaft. The park position for the CMP actuator and camshaft is 8.5 degrees before top dead center (BTDC), which is equal to 17 crankshaft degrees BTDC. The engine control module (ECM) can only command the CMP actuator to retard the valve timing from the park position, or advance the valve timing back to the park position. The total range of valve timing authority is approximately 20 degrees of camshaft rotation, which is equal to 40 degrees of crankshaft rotation
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Sunday, February 2nd, 2014 AT 9:36 AM
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
I forgot this part.
The camshaft position (CMP) actuator system is controlled by the engine control module (ECM). The ECM sends a pulse width modulated twelve volt signal to a CMP actuator solenoid to control the amount of pressurized engine oil, into the CMP actuator. To regulate the pressurized engine oil into the CMP actuator, the solenoid uses electromagnetic force on the solenoid pintle to pulse the oil control spool valve. The pressurized engine oil is sent to unseat the locking pin, and to the vane and rotor assembly of the CMP actuator, to either retard or advance the valve timing. The ECM will control the amount of "on" time applied to the solenoid.
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Sunday, February 2nd, 2014 AT 9:38 AM
Tiny
KEITH DOLPHIN
  • MEMBER
  • 5 POSTS
There we go. Another site has helped me with understanding how these actuators work like your latest response. Thanks. The last codes I got before I took it to the dealer were : 16, 17, 21, 154.

From what I understand, the actuator is not suppose to be stalling and the speeding up while rotating the engine by hand. I am going to change the actuator and the chains and hope for the best. Like I said before, I will post back what happened. If you have anything to state about the codes I just posted, I would like to hear it.
Thanks again for your time helping me.
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Sunday, February 2nd, 2014 AT 7:38 PM
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
It should be locked into the pin so it will not do what you are saying it is I really thing you only need the one actuator.
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Monday, February 3rd, 2014 AT 7:59 AM
Tiny
SHAWNSMITH0889
  • MEMBER
  • 9 POSTS
Is there a way to test the CMP actuator to tell if it is bad or not?
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Wednesday, January 20th, 2016 AT 8:58 AM
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
No, because it is controlled by the solenoid and engine oil pressure.
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Wednesday, January 20th, 2016 AT 12:12 PM
Tiny
SHAWNSMITH0889
  • MEMBER
  • 9 POSTS
So basically since they are kind of cheap I should just change them and hope that fixes it? My timing chains were already changed a little over a year ago so I do not think they would go bad again, I would not think anyway.
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Wednesday, January 20th, 2016 AT 12:17 PM
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
There is a spool valve inside so you cannot really turn them by hand to test them.
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Wednesday, January 20th, 2016 AT 12:57 PM
Tiny
KEITH DOLPHIN
  • MEMBER
  • 5 POSTS
Well, as it turns out, the dealer mechanics were wrong. The reason the vehicle would start and run until warm and shut off was that one of the catalytic converters was just about plugged solid. Managed to wreck that engine and a used one before finding that out.
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Wednesday, January 20th, 2016 AT 6:28 PM
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
If a catalytic converter was bad it should have thrown a 420 or 430 code.
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Thursday, January 21st, 2016 AT 5:48 AM
Tiny
KEITH DOLPHIN
  • MEMBER
  • 5 POSTS
That is the strange thing. It did not have those codes. It had lots of other ones though. I now have new catalytic converters and a new motor and I got a 420 code. I have a tech2 scanner. The rad side of the motor output o2 sensor not reading like it should. The other side is working fine. Swapped around the output sensors and still had a bad reading from the radiator side and good on the other. I think I have ruled out the o2 sensor. I bought a new cat for the radiator side just to make sure. Still getting 420 code and bad readings at output sensor. Used a digital heat gun and checked the temps at front and back of both catalytic converters. They are the same. I think it may be the wire that goes to the sensor but do not know how to test it. Dealer says that it is my aftermarket catalytic converters. They will not guarantee that their catalytic converters will solve the problem. They want $2,500.00 for two catalytic converters and two sensors (installed). Too much for them to guess with my money. Oh, I also changed the fuel injectors on the trouble side. Any ideas?
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Thursday, January 21st, 2016 AT 7:56 AM
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
These will cause a 420 code an air leak between engine and catalytic converter, a bad O2 sensor and a bad catalytic converter. You can pressurize exhaust system with 3 psi to find air leak if it has one.
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Thursday, January 21st, 2016 AT 9:34 AM
Tiny
SHAWNSMITH0889
  • MEMBER
  • 9 POSTS
Is there a way to test the cam position sensor?
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Friday, January 22nd, 2016 AT 12:28 PM
Tiny
SHAWNSMITH0889
  • MEMBER
  • 9 POSTS
I am wondering about the cam position sensor itself?
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Friday, January 22nd, 2016 AT 12:45 PM
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
See picture, but you need a scan tool like a tech 2.
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Friday, January 22nd, 2016 AT 1:13 PM
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
Sorry, image did not load for some reason. Basically pull cam sensor, leave hooked up turn key on observe the parameter counter on scan tool pass a metal object across it repeatedly the counter should increment if not replace sensor.
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Friday, January 22nd, 2016 AT 1:17 PM
Tiny
SHAWNSMITH0889
  • MEMBER
  • 9 POSTS
So we got my engine out and found out the timing chains jumped and and is way out of timing. When the mechanic went to turn the engine with his breaker bar it turns to a certain point then stops and you cannot turn it anymore. Does that mean valves or something mite be bent? It turns over fine when you turn it over with the ignition.
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Monday, February 8th, 2016 AT 10:32 AM
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
The valves may be hitting the piston if the timing is out. Check compression for bent valves.
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Monday, February 8th, 2016 AT 12:43 PM

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