Cayenne - not always starting. Only commonality is parked on a 'h

[Richard Zellmer]

In December I bought what I believe is a well maintained 2008 Cayenne base with 67K miles We normally keep in the garage - temp about 50F. It always starts fine from garage. However there have been a few occasions where we put a different car in the garage and parked it outside. Twice when parked outside it took numerous attempts to start. Last night was one of them, and it took a good 10 tries over 10 minutes to get it to start. The only difference from being in the garage is temp and the fact that the driveway is on a 15 degree hill.

As mentioned above it always started okay from the garage but I did notice a slightly rough idle for first 30 seconds on a few occasions.

Based on the slightly rough idle at startup i am thinking the cold and/or hill just exacerbates the problem and isnt the root case. I am in the process of getting the servicing dealer to send me the service records but was looking for some ideas and had a few questions

Seems like likely candidates here are fuel or spark.

1) I was thinking about purchasing Durametric software. Can I have error codes that Durametric would pick up without having a check engine light? I dont have the check engine light on and was wondering if I were to have codes would I always have a 'check engine' warning.

2)Plugs/Coils and their codes - I am confirming when the plugs were last replaced but if replaced on schedule at 40K I am not that far way from another replacement. They are check enough to just replace. If plugs/coils need replacement should I expect to see codes in durametric? Or is there a likelyhood of them needing replacement without any codes?

3) Other logical source of issue would be fuel delivery. Does this or any software measure pressure? Would a fuel pressure gauge be a iogical purchase to run this down? Weekend will be the first chance to really take a look so trying to figure out what (if any) parts/tools to order in advance.

Any other thoughts for root cause?

Edited February 18, 2014 by Richard Zellmer

[Doohan]

The Durametric is an extremely useful investment. In my opinion your problem could be a faulty temperature sensor or MAF...

Edited February 18, 2014 by Doohan

[Richard Zellmer]

Thanks... I am going order Durametric. My open question at this point would be - do I need to have a 'check engine ' indicator on to indicate there is codes that the durametric can find? I release this sofware can pull a lot of values out of the cars computer. My specfic question I guess is 'do all error codes that durametric can pull down also trigger an indicator on the dash that there are error codes?'

Edited February 18, 2014 by Richard Zellmer

[Ahsai]

Thanks... I am going order Durametric. My open question at this point would be - do I need to have a 'check engine ' indicator on to indicate there is codes that the durametric can find? I release this sofware can pull a lot of values out of the cars computer. My specfic question I guess is 'do all error codes that durametric can pull down also trigger an indicator on the dash that there are error codes?'

No, there are also pendng codes Durametric will log (and show you) that do NOT trigger the CEL.

[Pkscheldt]

+1 on the MAF as the issue

[Richard Zellmer]

I finally got durametric. No faults/code found. I did turn on some monitoring for the values from the MAF but other then the values go up when I hit the gas I dont know what the proper ranges are.

Any pointers on how to use Durametric to diagonis the MAF sensor?

[Pkscheldt]

Here are my 2 cents.... I clean the throttle body and the MAF every 50K. This is something I do in all of my cars and it has served me well. In my Cayenne I never had any codes associated with the MAF. The idle would just start to be a little less smooth, and I would have periodic slow to start periods when temps would drop. I'd take out the MAF(s) and spray them with CRC MAF cleaner. NEVER touch the sensor. At the same time while the MAF was drying safely I would remove and thoroughly clean the throttle body.

Some say to never clean the MAF and to just replace them, but I've found that every modern car I've ever had eventually suffers from a dusty/dirty MAF and is much happier when it is clean.

[Richard Zellmer]

I will have to check again tonight but I though when I ran durmetric (before it caused my laptop to crash) I only saw the measure of flow availble in durametric, not the voltage.
On a 2008 Cayenne base should I expect to be able to see MAF voltage?

I have MAF cleaner coming tomorrow from amazon.

[Loren]

A MAF would not cause a no-start situation. The car will idle and run low RPMs fine without the MAF at all (of course you will get a fault for the bad/missing MAF).

I would check the fuel pump delivery - a known problem on Cayennes.

[Richard Zellmer]

Loren - Since I dont get any MAF faults and from the way it sounds I dont disagree that fuel delivery is more likely. I am going to run a fuel pressure test tonight. Found procedure here
http://forums.rennlist.com/rennforums/porsche-cayenne-forum/590120-cayenne-s-stalling-problems-how-do-i-test-the-fuel-pump-2.html
so will follow this unless I see a better solution to test fuel delivery.

the kicker is that is always starts fine in my garage(where I keep it 99% of the time) but the last two times I parked it ouside in my driveway it gave me a hell of a time to starting the next morning. If my wife is running errands she doesnt hard time restarting on the return trip but that could be because the engine is still slightly warm. I am in NJ so it is cold this time of year.

[Pkscheldt]

I wish you well. This is Loren's house.... But, not trying to be argumentative I disagree that a MAF will not cause a "no start issue" in a Cayenne.

I agree that a car or specifically my Cayenne did/will start with no MAF, and that a disconnected MAF will throw a code. But "no MAF" is quite a different thing than a faulty MAF or a dirty/oily MAF, as disconnecting or having no MAF will default the system to a pre-programmed fuel etc setting which if the MAF is problematic will allow the car to start. In my case, a dirty MAF did create a very LEAN situation which resulted in slow to start activity and intermittent rough idle. This condition only happened for me in cold/low temps on two separate occasions. No codes were throne, except when I disconnected the MAF(s) and it started fine.

It could very well be a fuel pump issue as well.

On a separate note with respect to codes. I had several different instances over the years, including much later when my primary fuel pump went out where a code was never thrown for a variety of different engine system issues.

Best of luck to you!

Edited March 4, 2014 by Pkscheldt

[Richard Zellmer]

Well I think the next stop is for me to play with Durametric and a fuel pressure gauge and track this down...

[Richard Zellmer]

I had trouble starting today and it did generate two errors (both same). Code below - What is interesting is google searches on P0822 have almost no info. 'Porsche and P0822' only returns 1500 matches and only one seems relate to this issue and it is just a page that lists Porsche codes.

P0822 - Crankshaft position sensor "A"||circuit range/performance - Implausible signal, test conditions are not-completed, fault is not currently active and is not causing a DTC light

I am not sure if this is a symptom of the problem or just a code that is spun based on the fact that it didnt start. investigation continues.

[Ahsai]

Sounds like you're making some good progress. When you have trouble starting next time, you can pull an ignition coil (insert a spare spark plug or a spak tester) to check for sparks. If there's no spark, the crank position sensor is highly suspect. DME cuts fuel AND spark if good crank signal is not detected by the DME. Also, you can listen to the injector using a stethoscope or connect a noid light ni place of the injector to see if they are operating when you're crankng.

Edited March 5, 2014 by Ahsai

[Richard Zellmer]

I did get another code later - At least it is in the same family. camshaft rather in the crankshaft... :)

P0010 - Inlet camshaft control||bank 1 slow - Implausible signal, test conditions are not-completed, fault is currently active and is not causing a DTC light

My one concern is would crank position sensor problem match with the fact that in addition to starting problems the last few starts have had a bit of a rough idle until it warms up a bit? Ahsai - Are you saying that if it cant find the crank position it suppresses the spark completely. If so, it seems like this could explain a total start failure but might not be the cause of my rough idling on the last few starts.

.

[Ahsai]

Yes, if the DME doesn't get a good crank position signal, it doesn't even know at what moments it should fire the individual cylinders. Agree that does not explain rough idle though. Would still be good to verify spark and fuel injector clicking during hard start, just like what one would first check w/o a scan tool. Then presence of fuel pressure.

[Ahsai]

Btw, have you checked using Durametric if the coolant temp sensor is giving correct readings, especially when cold?

[Richard Zellmer]

Assuming that value shows up as engine temp it appears to at least generally work as the value was okay the few times i spot checked it.. My plan is to check fuel pressure this weekend and I agree if I can replicate the no start condition it would be worth while seeing if spark is present. This will help me tell if the no start and rough idle are same problem or two problems.

Thanks all for the help. Will post back after I test some more.. I do also have new plugs and air filter coming mostly because I don't know when last owner changed them. I wouldn't think either of this could cause these problems without error codes but couldn't hurt none the less.