2001 996TT:
Just finished rebuild and strengthening of 996TT engine and Tiptronic after 65K miles with Evo GT 640 tune. We upgraded to GT 660 software with Evo intake box and Hitachi MAF and 74 lbs injectors.
I keep getting DME errors P0171, P0174 and/or P1109 and/or P1126. Check engine light comes on at low power levels incl idle. Intermittently the car runs rough/rich and smells of gas with Short term fuel % trim above 20 and high lambda values. Other times the car runs perfect with Short term fuel trim around 0 and lambda values around 1.00. Check engine light comes on randomly in either condition, but always at low power levels.
Suggestions on where to start looking would be appreciated. Faulty MAF? Leaky intake system?

 

check all you wire connection and do a vacuum pressure test,check before turbo plumbing !
remember resetting ecu will make car run crappy for short term

good luck

 

i only like to say it could be your lamdba sensor...disconnect and try no cost for you

sometimes lambda sensors around 50000miles fail if it heat up

 

I just had the 1109 and was thinking MAF. After voltage checked out fine, I found mass boost leak and IC hoses blown off after 997.2 upgrade. Good luck!

 

Thank you all for input. I have studied the graphs of fuel trim % and lambda values. It looks like the most common occurrence is lambda going high followed by the fuel trim % going in excess of 20% when throttle is applied. I agree with the inputs that I likely have a leak in the intake system after the MAF, allowing more air to reach the cylinders, causing more fuel to be needed. The car is going to the shop Monday for vacuum and pressure test of the intake system. More input is always aprreciated. I will keep the group posted on the outcome.

 

One more tidbit and a question: I have noticed that my indicated and actual mpg are way off. When I last filled up I read 19.3 mpg on the computer but actually only got 14.0 mpg (mix of city and highway). Does the computer calculate mpg from the amount of air it measures? This would again indicate an airleak between MAF and turbos, forcing a richer fuel trim % compensation in order to keep lambda values where they should be.

 

Hey Olwe what upgrades did you do to your tip trans? I'm researching upgrades and mods now recently bought a 02 turbo. Did you get the evo tcu software? - thanks!

 

GT660 includes new larger fuel injectors which ECU is not compensating for. Your true mileage will now always be lower than indicated mileage...

 

Ok. Intake leaks fixed. This has reduced the errors to only P1109 (Input variables, charge measurement - Above Limit). No more P0171, P0174, or P1126. Does this provide any clues? My shop is suspicious of the boost pressure sensor and of Evo GT 660 programming.

I do have the Transmission CU upgrade and will comment on it as soon as I have better data.

TIA,
Ola

 

disconnect the maf... on a OEM maf the car runs just fine... may shed some light... it should be in limp mode...

 

that can be changed in the ECU adjust for the bigger injectors..

 

Just got my car back today after reprogramming by Evolution Motorsports. So far no errors. Keep your fingers crossed.
It looks like, once he intake leaks were fixed, the problem was in the programming. I have no idea what they chaned, but the car now seem to run better than ever, peaking at 1.4 bars.
I have still not evaluated the TipTronic re-tune properly. So far, I have not noticed any difference and have not seen it go to 7,000 rpm. That will be the next thing to work on...

 

Did EVOMs also re-tune the ECU to match the TCU? My car goes to 7k.

 

They did remap the ECU, originally to GT 660 spec's. What is in there now I am not sure as the tune is likely customized (I'll try to get more info from Evo). The car really runs very well, smooth and powerful under all conditions. I see 1.3 to 1.4 bars under full power.

As I have not seen the RPM's go over 6,700 I am not sure that the TCU re-map "stuck". Can you tell me anything else about your experience with the re-mapped TCU? How does it differ from OEM other than the higher rev limit?

 

olwe, I don't know if you would have a chance to drive the car in cooler weather since you're in FL; you'll see the car spikes to 1.6 once a while.

I stated my opinion many times about the TCU on this forum. Most people thinks the TCU re-tune not worth awhile, but I think the car drives much better than the OEM tune. I believe some people had an older version of TCU and the TCU re-tune doesn't apply much to it (what year is your car?). Mine was tune by Todd Z who originally created this TCU tune, while he was visiting ShareWerks in the Bay Area. He had to re-map the ECU along with the TCU re-tune.

Did you rebuild your Tip tranny when you meant "strengthtening it"?