Legitimate 'Limp mode' or not?

[SteveKen]

After less than two weeks of RS6 ownership, I'm (not so) happy to report a loss of power.

My wife has been driving the car, so I can't say how long it's been doing this. She thought I put the car in valet mode on purpose. lol.

Anyway, can someone define 'Limp Mode'??? Is it car won't go above xxxx RPM and xx MPH, etc.?

What textbook issues cause limp mode?

Is there any symptom/condition that could cause a condition to be mistaken as limp mode?

The current condition I have is that the car seems to back off once it hits 3500 RPM while driving. That's all I can tell. The engine revs fine above 3500 RPM when I've got the car in park, not moving, etc.

I've got no codes (ECU or trans) so I'm going to have to log some data (boost, EGTs) since all the STFA'ing I've been doing says that it could be a boost leak or bad EGTs (even though no code).

It's been raining pretty good here for the last few days. I hope that it's nothing water related.

[DHall1]

Reset the ECU.

Your car overboosted real bad on the log I looked at. That would give you limp mode.

[SteveKen]

Reset the ECU.

Your car overboosted real bad on the log I looked at. That would give you limp mode.

Thanks sir. I hope it's this simple.

What's the proper technique for doing this? I've always disconnected both battery terminals and touched them together. Not sure if it's going to be easier or harder with the rear battery?

I also hope to do some more logs for you folks. I might be getting my hands on a HEX cable this weekend that will allow more data to be collected.

[DHall1]

Disconnect the battery.

Your overboost will come back but its a good test for now.

I do not have Hex-can Vag and mine has turbo mode. I have the Key-II USB. You hit the turbo button before you start the logging process. Select your 3 channels and then hit turbo button then log button. LMK if that works

[SteveKen]

I've got the KEY-USB cable. I'll give it another shot to see if I did things out of sequence. FYI, I normally don't drive it that way. Only for scientific purposes. (never WOT, at least)

[skribe]

+1 disconnect the battery, takes two minutes. Pull the positive lead and short it to the exposed metal on the battery tray with a screwdriver or something. Do not electrocute yourself if at all possible.

Some limp conditions will disappear for ~250 miles if you reset. Some won't.

[SteveKen]

Reset ECU. LAck of power under load still seems to be an issue though. I'm pretty sure I've got a boost leak.

Maybe I'll get time to examine further tomorrow. . .

[yokust]

Most common issues are:

Lower Intercooler hose clamps have been hit and letting hose slide off intercooler
Seen clamps on turbo outlets get weak and jsut wont tighten up anymore
MAF orings on inlet pipes below airbox get damaged or missing causing all kinds of weird issues

[hahnmgh63]

And of course, OEM intercoolers have at least a 20-50% leak rate. Some leak more than others but from earlier posts I would say that the 20-50% number I threw out there isn't unreasonable. If you are pulling the airbox off to check the MAF's, also check the vacuum lines that you can see underneath the housing as they get a lot of heat sandwiched between the intake manifold & air cleaner housing.

[DHall1]

Please complete a few more data logs before ripping into the car. Try to pin down a certain area to look for.

3,31,115 again will tell you many items but starting with boost requested and actual.

[SteveKen]

Off top of your head, do you know what blocks monitor the EGTs?

[DHall1]

Log block 112

Off top of your head, do you know what blocks monitor the EGTs?