Grantsfo

OK so drove over 1000 miles with Cobb stage 1 tune and car was awesome! Tons of low end boost. Last week in middle of AX car lost significant amount of power roughly 100 HP. Really lost low end responsiveness. I could break wheels loose easily in first and second gear with tune and now can barely get them moving out of slow turns. Almost feels like eCU is limiting torque. Now car has very litte low end boost. Still seems to make near stock top end. Also one morning while driving almost felt like ECU was cutting power as opposed to a boost leak. Car felt like it was in limp mode.

Looking at boost gauge at low RPM making 4 to 6 psi and at higher 11 to 12 psi but car feels slower than stock now. Still makes some power but way off from what I had with tune. Will contact Cobb. Anyone have a sense of what might be going on? I was thinking boost leak but it feels like ECU programming is limiting power but Im unsure.

polobai

Have you tried to load the stock map/drive around and then reload the cobb tuned map?

ClassJ

Following....not the first phantom "boost leak" I have heard of with a tuned 991.2 platform.

I wonder if the ECU is still controlling things with torque limits behind the scenes.

S S

Have you kept your SW exhaust, or gone back to stock? If I remember correctly, you were using a Cobb provided vs pro tune as well, right?

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Grantsfo

Not yet. That's going to be my next step. Had a crazy week last week with family emergency so hoping to have time to do some detective work. I did quickly try to reset by disconnecting battery. That didn't help. In fact when I started car up it was cutting revs to like 2000 rpm. Then as car warmed up was able to rev.

Grantsfo

This is basic tune from cobb. Have had SW muffler since tune - don't think it has anything to do with muffler. Honestly I don't know that SW muffler increases flow that much more than stock sport muffler. Its just a lot lighter and sounds better to me. Couple weeks ago first sign of this issue with car feeling like it was in limp mode. Seems like there must be a sensor somewhere giving wrong signal to ECU or potentially a boost leak. Feels more tune and ECU related than mechanical leak but will see.

spdracerut

It could be an issue with the wastegate actuators. They are vacuum actuators, so they are held shut with vacuum. Without vacuum, they default to open. Sorta backwards from typical boost actuators which are naturally held shut and then opened by boost. So, if there's a vacuum leak to the actuators, they won't hold the wastegate valve closed which would account for very sluggish boost response. Might be worthwhile to check the vacuum hoses going to the actuators. Another possiblity is the wastegate arms getting seized/limited range of motion into the open position. Its not an unheard of turbo failure mode.

S S

I hear you, but all I've mod'd is the exhaust and it's definitely changed up the aspiration of the engine, not just noise or the weight on the azz... My money is on your ECU and associated not digging the mods. If it was a simple boost leak, as you've posted above and separately, some of the other drama wouldn't be happening IMO.

Good luck!

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911.

Check for any fault codes that could be stored?

991.two

Have you installed the latest version of the COBB tune, v105 for the 991.2 It was just released last month. Fixed all of my T problems with the COBB stage 1.

drcollie

No saying this is your issue, but years ago I had a tuner boost my turbos on my car, and it ran like a scalded day until it lost all its power and became weak, like what you describe. Turns out the overboost blew the head gaskets on my car, and it was an expensive repair. That was the end of modified boosts for me. Good luck.

groundhog

Sounds like a boost leak to me - likely the ECU pulling timing in order to stop running lean.

PTS-BRG

Return the car back to the stock tune. Download the latest off the shelf maps from the Cobb website and load it back on. You should be good to go..

GONEIN10

Boost leak, bad MAP or MAF sensor signal. Most likely a boost leak as the stage1 doesn't push enough boost to cause a head gasket issue.

GONEIN10

returning it back to stock wouldn't resolve a mechanical issue it's not like the software went bad.