08 Porsche Cayenne 3.6

Zakk Technician Texas Posted   Latest  
Resolved
Driveability
2008 Porsche Cayenne 3.6L (A 5501) 6-spd
Misfire

This vehicle runs a little rough only on a cold start then clears up and seems to be fine. Found no codes in any module but while watching misfire counters on the scan tool found the misfires to be slightly random but cylinder 6 seem to have the most. I swapped coils and it didn't seem to change but then every time I watch the misfire counters it's never really consistent. Pulled spark plugs and they don't seem to bad. The vehicle has 140k miles so I started with a BG platinum induction service and that didn't seem to make a difference. I then checked secondary ignition on cylinder 6 with a pico scope and I'm not a pro with analyzing these waveforms. Some events definitely look different then others but I'm not sure what to make of them. I have attached a file that is idle with a snap throttle. Please let me know what you guys see. Thanks

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Ray Diagnostician
Ontario
Ray
 

To invert your COP secondary, go to “Tools” then “Math Channels” then click on the “invert A”. You should scope the misfiring COP along with at least one non misfiring COP to compare. When you want to stress the ignition system, do a steady 1500 rpm brake torque. Set the scope to 500 ms/div and the sample rate to 6 MS. You could use the COP extension set to scope 4 cylinders at the same time.

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Steven Mechanic
Washington
Steven
 

Cold start misfires on direct injected vehicles is most commonly caused by fuel injector spray patterns that are bad and carbon build up in the intake ports. If I had this vehicle, I would sell six new injectors and clean the intake ports while the intake is off. Just a heads up if you order the fuel injectors, three of the injectors are regular length and three are extra long because this is…

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Agree
Bill Owner/Technician
Michigan
Bill
 

Steven's response is right on! I agree 100%. The only thing I would like to add is this ECU does a real poor job of flagging the correct cylinder misfires! It will mis report often & the only way to know what cylinder is misfiring for sure is to current ramp all 6 at the same time using a trigger and the firing order. You can grab all the B+ wires in the plastic loom that runs on top the…

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Ray Diagnostician
Ontario
Ray
   

Scoping the COP primary coil winding amperage draws will not show the rich or lean air/fuel mixtures in the cylinders. The secondary spark plug burn voltage can show the rich or lean air fuel mixtures in the cylinders. In the first capture, I'm doing a 1500 rpm brake torque and the left spark plug's burn voltage shows a fuel fouled spark plug and the right secondary shows the spark arcing…

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Bill Owner/Technician
Michigan
Bill
 

I don't disagree with you at all Ray. Your method will display more data if interpreted properly. Personally I seldom use secondary waveforms because I don't have the skills to analyze them properly… I am always impressed at your scope abilities and sharing of captures. Thanks for all you contribute here!

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Thanks
Zakk Technician
Texas
Zakk Resolution
 

So believe it or not but this car is still in my bay. Basically I found that someone in the past had removed the valve cover and when reinstalling it they broke the rear corner bolt that goes into the timing cover. Then they tried to drill it out but messed it up even more. So they decided to pack silicone around the broken bolt then finish it off with JB weld around the whole corner the the…

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