Cayenne S, new MAF solved idle issue, Rev much more free
03-20-2017, 02:03 AM
#16
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I was having similar problems with my 06 CS with 59k miles. The engine felt like it was running lean intermittently. I thought the fuel pumps were on their way out. At random, I would get a slight hesitation when accelerating or when turning. It would also idle slightly rough on occasion. So I changed all 8 coil packs and spark plugs with new ones. The rough idle got better but wouldn't go away completely and I still had that slight hesitation when accelerating. (It wasn't quite a delay in response to the gas pedal but more of quick loss of power before accelerating as if it wasn't getting enough gas when stepping on the pedal.)
So I came across this post and immediately thought I should try to clean the MAF sensors before ordering new ones. What I discovered is that both my MAF sensors were not completely seated into the plastic elbow that connects to the air box. It was barely noticeable. I discovered it when I was removing the sensors to clean them. This was letting unmetered air to enter the system. The U shaped wire/spring that holds the MAF in place was not holding the sensor flush on one side of the sensor. I had to bend the wire a little more to give it more tension. When I did that, it held the sensor flush with the elbow.
I also discovered that the MAF sensor has a specific angle that it sits at. There is a cut-out at the edge of the sensor that helps lock it in place. The right side/ passenger side is easily visible where it locks into place. The left side/driver side is not so visible because it locks in place underneath and you can only tell it's locked in place by feeling it with your finger.
Once I locked both MAF sensors into the correct angle and seated them properly into the elbow with the U shaped wire, I took it for a test drive and am happy to report that the rough idle completely went away and so did the hesitation/shudder when accelerating. I didn't have a CEL so I thought the sensors were dirty. I come to find out they were just not seated properly. I hope this helps other with similar symptoms.
03-20-2017, 08:50 PM
#17
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I know this is an old thread but this post saved me about $400 and I wanted to post my results to hopefully help other DIYers like me.
I was having similar problems with my 06 CS with 59k miles. The engine felt like it was running lean intermittently. I thought the fuel pumps were on their way out. At random, I would get a slight hesitation when accelerating or when turning. It would also idle slightly rough on occasion. So I changed all 8 coil packs and spark plugs with new ones. The rough idle got better but wouldn't go away completely and I still had that slight hesitation when accelerating. (It wasn't quite a delay in response to the gas pedal but more of quick loss of power before accelerating as if it wasn't getting enough gas when stepping on the pedal.)
So I came across this post and immediately thought I should try to clean the MAF sensors before ordering new ones. What I discovered is that both my MAF sensors were not completely seated into the plastic elbow that connects to the air box. It was barely noticeable. I discovered it when I was removing the sensors to clean them. This was letting unmetered air to enter the system. The U shaped wire/spring that holds the MAF in place was not holding the sensor flush on one side of the sensor. I had to bend the wire a little more to give it more tension. When I did that, it held the sensor flush with the elbow.
I also discovered that the MAF sensor has a specific angle that it sits at. There is a cut-out at the edge of the sensor that helps lock it in place. The right side/ passenger side is easily visible where it locks into place. The left side/driver side is not so visible because it locks in place underneath and you can only tell it's locked in place by feeling it with your finger.
Once I locked both MAF sensors into the correct angle and seated them properly into the elbow with the U shaped wire, I took it for a test drive and am happy to report that the rough idle completely went away and so did the hesitation/shudder when accelerating. I didn't have a CEL so I thought the sensors were dirty. I come to find out they were just not seated properly. I hope this helps other with similar symptoms.
I was having similar problems with my 06 CS with 59k miles. The engine felt like it was running lean intermittently. I thought the fuel pumps were on their way out. At random, I would get a slight hesitation when accelerating or when turning. It would also idle slightly rough on occasion. So I changed all 8 coil packs and spark plugs with new ones. The rough idle got better but wouldn't go away completely and I still had that slight hesitation when accelerating. (It wasn't quite a delay in response to the gas pedal but more of quick loss of power before accelerating as if it wasn't getting enough gas when stepping on the pedal.)
So I came across this post and immediately thought I should try to clean the MAF sensors before ordering new ones. What I discovered is that both my MAF sensors were not completely seated into the plastic elbow that connects to the air box. It was barely noticeable. I discovered it when I was removing the sensors to clean them. This was letting unmetered air to enter the system. The U shaped wire/spring that holds the MAF in place was not holding the sensor flush on one side of the sensor. I had to bend the wire a little more to give it more tension. When I did that, it held the sensor flush with the elbow.
I also discovered that the MAF sensor has a specific angle that it sits at. There is a cut-out at the edge of the sensor that helps lock it in place. The right side/ passenger side is easily visible where it locks into place. The left side/driver side is not so visible because it locks in place underneath and you can only tell it's locked in place by feeling it with your finger.
Once I locked both MAF sensors into the correct angle and seated them properly into the elbow with the U shaped wire, I took it for a test drive and am happy to report that the rough idle completely went away and so did the hesitation/shudder when accelerating. I didn't have a CEL so I thought the sensors were dirty. I come to find out they were just not seated properly. I hope this helps other with similar symptoms.
That will not cause unmetered air - since the MAF itself is "downstream" from the potential leak source. IIRC there is an O-ring on that joint, so it doesn't have to be absolutely perfectly seated, although good practice would be to check it is seated whenever it's disturbed.
I do suspect that cleaning the sensors may be what contributed to the better running engine you're experiencing. There can be "backstreaming" - which seems counter-intuitive - but oil vapor can travel back up the intake path especially when the engine is stopped. Service spec's don't call for periodic cleaning of the MAFs - but it would be a good thing if it's done carefully with the correct product (IMHO "CRC MAF Cleaner".)
One other thing worthwhile doing is cleaning the throttle body. It can also get gunked up from backstreaming oil vapors condensing on the butterfly and throttle-body throat. Remove the Y connector leading to it - then I usually remove the throttle-body to clean it (easy to do) - but it could be done with it in place. Be careful moving the butterfly - you don't want to break the stepper motor that controls it.
