So, I've recently had a couple codes pop up (P2189 and P2187) "lean at idle" on both banks. From some research I've read that it could be due to a vac leak. In unrelated news I had been meaning to get around to this job, but I recently did fresh coils and plugs about 150mls ago at this point. Those codes came on prior to me doing the job a couple weeks ago. Now on my drive home from work yesterday afternoon the idle seemed a bit rough, rougher than normal. Drove fine, idle was really all that seemed off. So I checked for codes once I got home and it showed another code of P2097 "post catalyst fuel trim too rich" so thought to myself this is a little odd. Decided to take the car for a quick coffee run this morning to see if the problem(s) persisted, and after stopping to get my coffee, upon startup the idle was very rough, and I was getting multiple misfires. Checked codes again once I got home "multiple random misfires detected"
I'd be shocked if all this is resulting from a vac leak, but Im kind of at a loss at what could be causing these misfires and the rough idle as well as this new "post catalyst" code. Any input would help. Much appreciated.
Im wondering if an AOS starting to fail could cause this. Im wondering if the membrane starting to go would cause my "lean at idle" codes, as well as possibly some oil seeping thru causing my misfires. However, Im currently not burning thru any oil as my level has stayed the same over the past hundreds of miles. I do get an interesting sound on cold start until the idle lowers, almost like a soft popping or bubbling. Im also not getting any smoke on start-up which is an AOS failing symptom. Just trying to think out loud. Any help is appreciated.
I would start by rechecking your coils to make sure all of the electrical connectors are well seated.
It's perhaps just a parallel to this - but my Cayenne exhibited similar symptoms and error codes. It turns out that Variocam PLUS consists of two variable functions on the camshaft - it changes timing (the obvious one) and it changes duration and lift (the not at all obvious one.)
The duration/lift change is a simple step function (changed or not-changed) done by changing the the height of the hydraulic valve tappets. This is done via an oil-circuit controlled by a solenoid in the head (one for each head.)
The only reason I'm suggesting this is - when I suggested this as a possible cause for the same symptoms on my Cayenne Twin-Turbo, the independent shop wasn't surprised although they never had seen it happen on a Cayenne. They had seen it happen a number of times on the flat-6 engines with VarioCam-PLUS.
Turns out that was the problem on my Cayenne, and $700 later it's running fine again (part was around $200, labor about 3 hours - it's on the back of the engine and not simple to get to..
Porsche
probably would have insisted on pulling the engine.) Dunno where it is on the flat-6, lets see if AllData shows it..
They admit that it exists, but I haven't been able to find where it's attached to the engine.
Found it!
What isn't clear is if the solenoid is outside or inside the valve cover. Someone will have to crawl under and look..
