High idle, power loss, no sport mode or cruise control

[stphnsns]

Hi guys, I have an ongoing issue on my 2006 C4S coupe, that I've been chasing off and on for about a year. I revised an old Renntech thread, but didn't get any replies, so thought I'd try over here, and see if anyone has any insight!

Essentially: Higher than normal idle (1200-1500: goes up as car warms up), lack of power upon acceleration (probably 50-60%), and failure of sport mode to activate. Those are the primary symptoms. Now I just noticed that cruise control won't activate (light on dash works when you first turn the key, but no light or cruise when you try to activate while driving). We replaced the throttle body last year, and thought that did the trick (seemed to for a while). I just this week replaced the gas pedal assembly, as I've read - like the TB - the potentiometer in there can fail. Also in the last year, we've replaced the water pump, AOS, and drive belt. My lucky year! Anyway, after about 3,000 miles, the problem has returned. It did a couple months ago, but after disconnecting the battery, it self corrected - for a time. Now its back and nothing I do seems to help. I removed the MAF completely, and the idle drops down to normal-ish, but there is ZERO acceleration. I assume that tells me the MAF is good? My other hint is from Borrowed knockoff Durametric software, I got the following readings (there has been NO CE light through any of this, and yes, the CE light bulb works)

Codes:

P1514 - FACTORY FAULT CODE 540 - THROTTLE JACKING UNIT LOWER MECHANICAL STOP

P1511 - FACTORY FAULT CODE 543

P2126 - THROTTLE ADJUSTING UNIT - POTENTIOMETER 2

P2121 - THROTTLE ADJUSTING UNIT - POTENTIOMETER 1

P1517 - THROTTLE JACKING UNIT ABORTION OF TEST

I believe that test was while running. When tested not running, the only readout was P1514.

Those codes would indicate the TB or pedal, but to no avail. One other consideration is the clutch cruise control switch? Hate to keep throwing money at it. Unfortunately, no dealer - or really even a qualified indy with Durametric anyway, close by.

Would love to hear if anyone has any insight or related experiences. THANK YOU!

[Jeff Alton]

Is that 1511 or 1551?

[Jeff Alton]

Likely a TB, but more testing required.

[Uwon]

My 2cents. Before you throw more parts ($$$) at it, get yourself a proper Durametric (you will need it as time goes on) and stop chasing with a knock-off equipment. OR surely there has to be an Indy in/near Elkhart with a PIWIS and have it flat bedded.
Good luck.
Johan

[stphnsns]

Thanks for the comments. The code in question is 1511 (also 1514). I plan to scan it again, just for kicks, now that we've changed out the gas pedal assembly, as that's what those codes would seem to refer to. The throttle body was the first thing we changed a year ago. And while I've heard of faulty new equipment, I'd be surprised if the new unit exhibited the exact same faults as the old. Do still have the original though, and thought about throwing it back in, just to see if it makes a difference.

Also, I haven't ever replaced the alternator to starter ground strap, and do get slow cranks at start up, when warm. These symptoms don't really seem related to that, but we all know what crazy things poor grounds & lack of proper voltage can do, so wondering if that could be a possibility. Thanks again for the comment, and yes, the search is on for a qualified regional indy. There are some "European specialists" around, but I don't know of any with Durametric, and I have heard of a few doing more harm than good when working on P-cars.

[Uwon]

^^^Sounds like it may be time to join AAA and ship it to Porsche Fort Wayne......
Johan