Hoping for some help from this experienced crowd. I recently got an AccessPort for my 997.1tt and am seeing a lot of knock and ignition timing being pulled, even on the stage 0 tune in normal mode. I've replaced plugs and coils, and fuel & air filters are only a few months old. Tried different gas, tried adding an MMT-based octane booster to the gas, tried running with MAF sensors unplugged, checked that FPR line was attached - nothing seems to have an effect. I'll paste a chunk of log below. Could this be O2 sensors? Those are the only thing I can think of that haven't been changed.

What are the other possibilities I haven't thought of? Any further debugging anyone can suggest besides taking it to the dealer and letting them figure it out? Thanks!

 

My first guess would be poor gas but you say you've already tried different gas and octane booster. You are in BC? How is the gas in your area in general? An OTS tune shouldn't be doing that. I would contact COBB support.

 

You are running the proper octane of gasoline?

On a related note you can try Techron. I use the bottle that treats 20 gallons of gasoline but dump the entire bottle in the gas tank then fill up the gas tank with the proper grade of gasoline and just drive the car normally. The rule of thumb is after the tank with the Techron is way down if you notice any improvement dump in a 2nd bottle and fill up the gas tank and drive this tank with Techron out.

My recommendation would be to plan on using 2 bottles -- one at a time! -- regardless.

Afterwards it is a very good idea to change the oil/filter as the Techron increases oil contamination.

From the data nothing really jumps out at me.

I have no 997 Turbo experience but I can tell you with my 996 Turbo (stock) at 132K miles when I had all 4 O2 sensors replaced -- there was one triggering a P0135 error code shortly after engine start but the engine was running without any untoward behavior -- after the O2 sensor change the engine was running noticeably better. Kind of surprised me the performance fall off that had occurred over time from the sensors "aging" I guess.

The #1 sensors are wide band to help with more precise fueling. If the sensors have some miles on them you might consider replacing all 4.

You have already replaced the coils but I'll also add that at around 140K miles when I had the coils replaced along with the plugs even though the plugs had around 10K miles to go before they were due to be changed on miles the engine perked up again rather noticeably. Now I have had the plugs changed before and the engine never ran any better afterwards so I attribute the improvement to the new coils. Again rather surprising the amount of performance drop off from the coils "aging" I guess.

 

I think gas may actually be the problem. I first tried it on the Chevron "94" octane we have here. That gave some pinging with the 91 OTS tune, so I switched to an Esso 91 octane which I (mistakenly it turns out) believed contained ethanol, unlike the Chevron 94. (Ethanol is an anti-knock agent, and the Cobb tunes expect E10.) This gas is definitely worse, which would explain why it isn't performing well, even going back to the stock tune. (Although I am surprised that I would get this amount of knock on any so-called premium, top-tier gas on the stock tune.)

This post covers all the gas fun in more detail: https://rennlist.com/forums/997-turb...l#post14268680

TLDR: I need to try a better gas again, and see if that improves things.

 

Definitely replace the o2 sensors. If they are original - several years old, they are not responding as quickly which is part of the feedback loop for the Ecu to control the fuel mixture. That was the first advice Cobb gave me when setting up our car. Mainly the 1st sensor which is the wideband one.

 

What intercoolers do you have? I know on my car once I changed out the stock ones with the AWE's it pretty much fixed the problem.

 

Your afrs seem to be fairly lean, target under peak load is usually around 11.5 to 12.