guys
my car has been running a bit slow lately. So i did some datalogging..
lamda's are ok. everything is ok. BUT, the car pulls timing like crazy.

im not sure why the car is pulling timing. There are no misfires, no boost / vacuum leaks. NO CEL's.


what do you guys think ? Im thinking maybe the secondary fuel pump is bad ?

also, my exhaust tips are WHITE after a few hard driven miles...

 

Data log the short term fuel trims and see what they are doing. Could be the car has a fueling issue, and the short terms will tell you if that is the case.

Could be a bad tank of gas as well.

Feel free to shoot me the durametric logs if you would like. Happy to take a look.

mitch.mckee@cobbtuning.com

-Mitch

 

Mitch I am continually amazed by your support even to folks without your products!

 

+1


It's awesome.

 

Is it pulling timing or just tapering off at high rpms?

If actually pulling timing, the biggest culprit would be knock. Did you switch gas stations recently?

 

wow. Thanks Mitch !
appreciate it greatly.
i dont know how to actually save the logs lol
i had Tim in the car with me, and he said either my APR tune is on the 100ct map (as the car pulls timing almost immediately when im WOT), or it could be the second fuel pump.

 

Chris,
its pulling timing almost immediately. theres definitely knocking.
its not the gas, as ive used different gas stations (usually Mobil). i datalogged on saturday, and i filled it up again yesterday, and its the same.

the car is down a significant amount of power.
i did some 60-130s on saturday and i was about 2 seconds slower than im supposed to be.

i have RSS semi solid motor mounts, but so do tons of other people, and no ones had knock because of them..

just for reference, at idle , the timing was at 35 degrees. at idle in sport mode. in normal mode its less.

 

Log the file and then I think it says export saved data maybe? It has been a while since I have used a Durametric. You can export it as a .csv or a excel worksheet I believe. If you can get it exported as a .csv and email it that would be great.

Let me know!

Thanks,

Mitch

 

Usually Misfires would trigger more simple fixes (Old Spark Plugs, Coils, Bad Gas/Sub-Target Octane), but if the car is Pulling Timing it sense something in the background is off (like Mitch + Tim said, plausible your fuel trims are maxed out and pump is dying).

Besides the obvious variables (Lambda/Boost/Timing), lots of background channels that should help narrow down what's "Off".

 

As Mitch mentioned double check the fuel trims. Try to datalog both short term and long term trims and see where they land at idle, cruise and WOT. If they're far outside the normal +/-10% range something is off. FPR line has been brought up as a common cause but it can also be fuel injectors slightly outside of spec. Given your car ran better on the same hardware before its hard to say anything but logs will certainly clarify it.

 

what steps should he take?

15 minute cruise around town ?
WOT in 4th (2200 RPM to redline) ?
idle for 2 mins ?

 

i did wot in 4th twice. gotta wait til saturday to do datalogging.

 

Here is what I recommend doing when diagnosing and tuning fueling and monitoring fuel trims:

Get the car warmed up fully at idle, turn it off, and reset ECU. Reset is available on the Cobb AP and Durametric.

Start the log and log the warm idle without touching the throttle not to induce any fuel enrichment table activity in the DME. End the idle log.

Once that is done, take the car on the road and do a cruise log steady speed say in 3rd gear and record that as well.

Send it in for review and adjustment. After the trims look good at idle and cruise log them at WOT, review and adjust.

Tuning this on a 997.1tt will involve potentially multiple tables such as injector scaling, offsets, fuel correction maps but always first start with any obvious hardware/mechanical issues such as an unplugged FPR line or less so obvious a dirty/old/high mileage fuel filter.

Dzenno@PTF/PTG

 

Sounds like it could be fuel delivery related. Here is a video I made a couple weeks ago, you can check the FPR line with your phone camera and see if it's still connected. Easy to do, even in the dark. Just turn on a flashlight app (or built into IOS) before using the camera. Logging short term fuel trims as suggested above is the best thing to do though.


Keep in mind though that ignition angle at cruise/idle are VERY different than under load. 30 degrees -> 16 degrees is very normal at say 3000rpm when you floor it. You should see it drop when boost comes up, then raise as RPMs rise. What you are looking for is after it settles under load, that it ramps up smoothly without suddenly dropping or with large variations. It will peak somewhere between 14 degrees @ 7000rpm on pump gas and 20 degrees @ 7000rpm on race gas. Plus or minus depending on your tune.

 

Didnt u have to replace a fuel pump relay recently? Could u have cooked the fuel pump?