2008 Cayenne S Rough Idle

[Cterry77]

So I've searched and searched and haven't seem to find the answer I'm looking for. A few weeks ago I got an O2 bank 2 sensor 1 code. Figured it was bad gas or dirty injectors. Ran some cleaner through it and a few fresh tanks. Last week it started idling rough and surging in park and drive at a stop. Acceleration was good but could still feel a rumble so I pulled the codes again. Had a misfire on cylinders 4-6, random misfire code, O2 still cam timing and such. Changed the plugs and coils and air filter. Still having the same issue. I've checked the plugs and check the coils and all are good and seated. Checked the connectors and they are all pressed in firmly. As I've seen some talk about the battery I have checked it. Voltage was a little low so I had it tested and found it was bad and replaced that. This all started about the same time the temps out here started to drop. Also checked the gas cap and that looks fine as well. Cleaned off the seal on it and made sure it was tight. I've built plenty of cars in my life and tuned as well but this has me stumped. Any suggestions are welcome. Here are the codes it was throwing before I did that work. 

P2254
P2a03
P0442
P0014
P0300
P0305
P0304
P0306

Still throwing the P2254 code, P2a03, P0442 and a P0017. I doubt the cam sensor is bad and with the surge in idle I'm sure the computer is trying to correct the timing the best it can do. I haven't changed the O2 sensor yet because after seeing the plugs and coils I don't think the O2 is bad just been reading a bad mix coming from those 3 cylinders. Spoke with someone today that thinks it might be a bad hydraulic tensioner for the timing chain. Any helpful insight would be great. 

Thanks

[czeitner11]

Try looking at the "Oil Separator"... I just got my 08 cayenne back from the local Porsche shop and was having the same issue at idle in park/drive. Mine happened after running a can of Seafoam thru the fuel and crankcase. It was still drivable for a few months until the separator finally gave way. $1377.00 later she runs like a champ.

[Cterry77]

I did run seafoam thru the motor few weeks ago to clear out the carbon but I've got the 3.6l and I don't believe it has the oil separator on it. I have looked and haven't found one. I am leaning a little toward getting a new fuel cap since it keeps throwing the P0442 code at me. Is it possible that these motors are so sensitive to pressure that a faulty fuel cap could cause the bad idle? 

[Fmscell]

So I've searched and searched and haven't seem to find the answer I'm looking for. A few weeks ago I got an O2 bank 2 sensor 1 code. Figured it was bad gas or dirty injectors. Ran some cleaner through it and a few fresh tanks. Last week it started idling rough and surging in park and drive at a stop. Acceleration was good but could still feel a rumble so I pulled the codes again. Had a misfire on cylinders 4-6, random misfire code, O2 still cam timing and such. Changed the plugs and coils and air filter. Still having the same issue. I've checked the plugs and check the coils and all are good and seated. Checked the connectors and they are all pressed in firmly. As I've seen some talk about the battery I have checked it. Voltage was a little low so I had it tested and found it was bad and replaced that. This all started about the same time the temps out here started to drop. Also checked the gas cap and that looks fine as well. Cleaned off the seal on it and made sure it was tight. I've built plenty of cars in my life and tuned as well but this has me stumped. Any suggestions are welcome. Here are the codes it was throwing before I did that work.

P2254

P2a03

P0442

P0014

P0300

P0305

P0304

P0306

Still throwing the P2254 code, P2a03, P0442 and a P0017. I doubt the cam sensor is bad and with the surge in idle I'm sure the computer is trying to correct the timing the best it can do. I haven't changed the O2 sensor yet because after seeing the plugs and coils I don't think the O2 is bad just been reading a bad mix coming from those 3 cylinders. Spoke with someone today that thinks it might be a bad hydraulic tensioner for the timing chain. Any helpful insight would be great.

Thanks

Hey Cterry77,

I've been waiting to post this, I just got my Cayenne S back from the shop (same year as yours). My issues were a cam code (bank 2) which came back immediately after clearing....caused a weird starting issue (crank/stop...crank/start) & a slight reduction in power. The shop traced the faults to the timing chain being out of sync. They took the intake manifold & valve covers off & re-timed the engine using special fixtures to lock the camshafts in place. Both banks were out of sync, since the intake manifold was out they carbon blasted the intake valves. Got it back and WOW, what a difference. Loads of power, transmission shifts better, no more starting issues. I forgot just how beautiful this engine really is.... I'm not saying that you're problem is the same as mine but my issues were solved :)

[rpcc]

Fmscell - what did that work cost?

[sportplus997]

So it's an S or a base? If it's a 6 cyl on the back of the valve cover left side when looking at it, little pin hole in cover if you put your finger over it and it's pulling vacuum and idle changes... You need a valve cover... Do you know what your fuel trims look like?

[sportplus997]

Still throwing the P2254 code, P2a03, P0442 and a P0017.

What is the p2254

P2a03 is fuel pressure sensor code?

P0442 tank vent/leak?

P0017 cam sensor?

[jlukas]

My Cayenne S had very similar issues prior to my purchase.  The solution (from iAutohausAZ) was replacement of the High Pressure Fuel Pump.  You might try that or suggest it to your service tech.

Edited March 29, 2016 by jlukas

[SpawnyWhippet]

I too would love to know the cost and man hours on this one. My CTT has the same issue, I am getting quotes for 30+ hours labor plus lots of parts, close to $10k total

 

 

Hey Cterry77,

I've been waiting to post this, I just got my Cayenne S back from the shop (same year as yours). My issues were a cam code (bank 2) which came back immediately after clearing....caused a weird starting issue (crank/stop...crank/start) & a slight reduction in power. The shop traced the faults to the timing chain being out of sync. They took the intake manifold & valve covers off & re-timed the engine using special fixtures to lock the camshafts in place. Both banks were out of sync, since the intake manifold was out they carbon blasted the intake valves. Got it back and WOW, what a difference. Loads of power, transmission shifts better, no more starting issues. I forgot just how beautiful this engine really is.... I'm not saying that you're problem is the same as mine but my issues were solved :)

 

[Fmscell]

I too would love to know the cost and man hours on this one. My CTT has the same issue, I am getting quotes for 30+ hours labor plus lots of parts, close to $10k total

Hey Cterry77,

I've been waiting to post this, I just got my Cayenne S back from the shop (same year as yours). My issues were a cam code (bank 2) which came back immediately after clearing....caused a weird starting issue (crank/stop...crank/start) & a slight reduction in power. The shop traced the faults to the timing chain being out of sync. They took the intake manifold & valve covers off & re-timed the engine using special fixtures to lock the camshafts in place. Both banks were out of sync, since the intake manifold was out they carbon blasted the intake valves. Got it back and WOW, what a difference. Loads of power, transmission shifts better, no more starting issues. I forgot just how beautiful this engine really is.... I'm not saying that you're problem is the same as mine but my issues were solved :)

Hi all,

Sorry for the late response, as for the work I described above, not too many parts here (intake + valve cover gasket sets, misc parts etc) probably totaling $250-300ish? Labor is roughly 8-12 hrs worth. The teardown is pretty much taking out the fuel injectors, intake manifold & valve covers, there are access holes to adjust the chain & while you're there carbon blast the intake ports (a must!). 30+ hours to do that work on a 4.8L sounds like much, IMO......Make sure the mechanic or garage you take it to has the fixtures to lock the cams on this type of engine, you want someone who's done this type of work before. These engines are like swiss watches, very precise & sensitive.

Hope that helps?!

[ekstroemtj]

Great. Thank you