chamilka

I apologize for the very long write up. My intention is to provide every possible detail so you can help me nail this problem.
Vehicle information: 2004 Porsche Cayenne S/ 114,000 miles.
Main Problem - Intermittent rough idling:
The engine runs rough intermittently. I have not been able establish any pattern as to when the problem would occur. Sometimes the car can be driven weeks without issues. Sometimes the issue is mild and sometimes severe. In one occasion, the car became not drivable. This has been going on for about six months or so. The shop has attempted to remedy the issue many times but the faults would come up after about 100 miles.

Following are the set of faults we see each time the problem comes up:
Bosch Digital Motor Electronics 7.1.1
Current Fault Codes (12/06/2013)
P0011:A Camshaft Position -Timing Over- Advanced or System Performance B1
P0431:Catalyst System Efficiency Below Threshold Bank 2
P0351:Camshaft Position Sensor "A" Circuit Intermittent Bank 2
P0300:Random/Multiple Cylinder Misfire Detected
P0301:Cylinder 1 Misfire Detected
459:PCM2 - No signal/communication, test conditions are not-completed, fault is currently active and is not causing a DTC light
1520:Rain sensor/light sensor
2197:Potentiometer for footwell lights

Following is a list of things that have been done with the intention of remedying the problem. I will also add to the list other strange things that seem to happen in conjunction with the main issue being discussed (in case there is relevance). The car has been looked at many times by a qualified local Porsche shop and they are running out of options too.

11/19/13 - Camshaft Position Sensors (Bank1, Bank2) were replaced
11/07/13 - All spark plugs have been replaced
11/07/13 - Swapped the two Coil packs: Cylinder 1 and 3: the misfire remedied soon after, but per this post the issue is back.
10/14/13 – Replaced Bank 2 rear oxygen sensor. The technician thinks the Catalyst convert could be bad, however he does not think the intermittent rough idling is caused by the bad Catalyst convert. His reasoning is If the Catalyst convert is the underline issue then the problem will not be intermittent.
11/19/13: Drained water from the chassis rails. While doing this routing water draining the technician mentioned that there may be evidence of un-drained/collected water leaking into the body. They suspect airbox/cowling to be the source of water intake to the body. He suspects water / wetness may be causing DME and control modules to fault.
To supplement above theory, I like to mention an electrical glitch that happens often. The radio acts up (turn on and off rapidly by itself) intermittently. Whenever this happens the rough idling (fault errors) problem also appears in fed days/weeks. Any relevance?

So based on the information above, what do you think my next step is. I truly appreciate your input.
Chamilka

chamilka

Well we are going to replace all coil packs. I will let you know if that takes care of it but I think there is some other issue here. The shop suspects the harness packs to be the culprit.

extanker

i do not like the fact that you replaced the camshaft sensors but are still getting a code. maybe check for a mechanical problem in the camshaft mechanism ?

XR4Tim

I thought about that, but I don't think you'd get a circuit malfunction from a mechanical problem. You would certainly get the timing error, just not the circuit fault, which points to an electrical issue.

mcbit

Could be something as simple as a bad ground causing an intermittent zero/ low voltage.

chamilka

You guys might be on the right track, the shop also thinks this is an electrical issue, however troubleshooting open-ended electrical issues can be cost prohibitive.
Interestingly, today the engine light went away but the when I ran the diagnostic tool there was a new error in addition to the previous once, here it is:
“907: Load management operat. on vehicle electrical sys./DME control module - No additional fault status available, test conditions are not-completed, fault is currently active and is not causing a DTC light”
On a previous post someone explained that this could be a battery or electrical issue. The battery is new.

Is there a systematic way to troubleshoot the electrical issues, where would you start?

Cole

Is this a dual battery cayenne? When was the last time you replaced the batteries?

SCOTITUDE

id start with fresh batteries.....low voltage causes many gremlins in the p!g.
Clear all the codes and start from there.

Dan87951

Have you done a compression or leak down test on the engine? I had a friend with a rough idle condition with his S and it ended up being a scored cylinder. Compression was so low it wouldn't combust. Hopefully this is you!

chamilka

Battery is fresh, this has only one battery. The rough idling is intermittent, so if you have low compression then you would not experience intermittent rough idling I though?

Nacho82

chamilka,

How exactly would you describe the way the thing runs when it is "running poorly"? I followed your PSM failure page and saw a link to this post and came over to see what you were experiencing.

I am having the PSM failure workshop error, check engine light, and had long issues with the four wheel drive system faulty error showing up. In the past, nothing ever caused the car to run poorly. Recently, I noticed when starting, the starter seems to run after the car starts up and this is a sign (has been each time anyway) that it is going to run like a turd. Sure enough, if the PSM failure triangle and counterclockwise circle with arrow error icon shows up on the dash, it runs like it has a miss, or in some level of limp mode. Sometimes, you can restart it and the starter doesn't run after it fires and the car will run like a champ.

Sorry for giving you a story to work through and no real help, but I am wondering if you have a similar performance issue with your problem. I don't have a scan tool, but I might need to invest in one to figure out my problem. If the issue is similar, I want to try and use the steps you took to help isolate and maybe try some new steps that I can come up with. Possibly giving you some possibilities to try.

chamilka

Hi Nacko82.
The PSM error went away not sure what I did, I did change the tires and brakes and wonder if that did the trick. There was no “thud” sound just poor idling and sluggish performance. I would like to update that the Cayenne stopped completely several weeks ago due to a Fuel pump failure, upon replacing the car seems to behaving better but still experience very slight rough idling which was diagnosed as “bad camshaft actuator in bank1.

Nacho82

Did you have the poor performance every time you drove, or were there times where you would start the thing up and maybe it would run fine.

Then at some point while driving the PSM error would pop up and all of a sudden it seemed like the thing lost at least 50% power?

I came across a few posts on various sites that people thought the issue could be a weak battery, weak alternator (not putting out enough juice), or something related with the throttle plates/MAF sensor. It is interesting that you had the fuel pump go out as well. I thought of a possibility of that maybe starting to die off on me. What is weird is sometimes I start the car up and it runs like a champ, but after a short drive down the road it will just bang like it is dropping into a lower gear and the PSM error pops up on the display and it starts running like a turd. After that point, it is game over. I can watch the tach do some bouncing while running when the PSM error is on as well. It will fluctuate instead of running steady.

As I mentioned, I think my only real fix is to get the scan tool and pull down some codes. Then figure out which ones I show might be the ultimate cause of the problem.

Jaxx52

Did you ever get to the bottom of this problem? I have 2004 Cayenne S similar codes/similar symptoms. Found electrical issues, plugged sunroof drain-- services fuse box, replaced main relay 167 under the hood p/n191 906 383C which was getting hot, replaced plug and coil in cylinder 1 (the only one throwing the code). Nothing seems to help. Also sulfur smell out of exhaust but no cat codes. My next step is MAF sensor but if you have any insight that would be great.

Thanks

chamilka

Hey Nacho82 and Jaxx52
II had the same exact set issues you both mentioned above. I too smelled sulfur time to time. The Fuel pump took care of some of the issue but I still would get remaining set of errors. My battery was good each time I tested it. However recently I replaced the battery since many forums talk about battery being very illusive, guess what? no more errors what so ever. I had done close to 300 miles and no errors. I had the car inspected for emission and safely- passed with colors  .
So I would say just replace the battery first, just do it.
Chamilka