Fuel Trims dont change!!

[matt98eclipse]

On my datalogger with mmcd I knoticed that my fuel trims dont change at all! What would cause this!! Im trying to tune with MAFT. Please help guys!!

 

[turborebel]

What are they? They could be maxed out. If not, they should change when you change your settings on the translater. Is your O2 reading healthy?

 

[matt98eclipse]

All my trims stay to 100% and wont change at all. I tryed resetting my ecu to see it that would help, but nothing. I orderd a new o2 sensor from oxygensensors.com and should be here tomorrow or tueday!!

 

[2gGSX]

Check for a DTC. Your car is not entering "Learn Mode" either due to a DTC, or you're not meeting the requirements:

* Coolant temp >= 190F
* Intake air temp < 123F
* Baro >= 22.9 inHg
* Baro <= 31.6 inHg

These are 1g specific.

 

[matt98eclipse]

2gGSX: What do u mean my by "Learn mode"?? Also what does DTC mean?

 

[2gGSX]

DTC means the ECU is throwing an error code, which should trigger your check engine light to turn on.

Learn mode is how the ECU adjusts your LTFT. It will first see if STFT is operational, and then, it will check to see whether or not those above points I mentioned are met. If both are true, and STFT is positive or negative for long enough, then the ECU will begin to adjust LTFT.

 

[dsmsucks]

Man have fun trying to find out why. I had my ecu rebuilt, new o2 sensor and coolant temp sensor. None of them solved the problem

 

[matt98eclipse]

Thats weird because not getting any check engine light at all!! My temps do reach around 200 I will have to check all the other requirements!

 

[2gGSX]

I'd recommend running the DTC check anyways--I had the same problem only to find out that the previous owner took out the bulb for the CEL light.

 

[dsmsucks]

Thats weird because not getting any check engine light at all!! My temps do reach around 200 I will have to check all the other requirements!

Same here brother, I to wasnt getting a check engine light and temp was good I gave up after while.

 

[fourreGsixty3]

Thats weird because not getting any check engine light at all!! My temps do reach around 200 I will have to check all the other requirements!

Not all DTCs set off the CEL.

Also the exact meaning of DTC= Diagnostic Trouble Code aka DTC

 

[steve]

If your basic setting are too far off the ECU will try to enter closed loop and once it exceeds it's programmed change in fuel setting and the O2 doesn't switch it will give up. So if your O2 isn't cycling at idle your trims will never change even if you meet the other requirements.

 

[matt98eclipse]

Hey guys my fuel trims still wont change i have bought a new o2 sensor and a new coolant temp sensor and still nothing!!! Please help guys (steve)

My o2s do cycle at idle. but not when just crusing! I have a log i can post to help if needed.

 

[steve]

Hey guys my fuel trims still wont change i have bought a new o2 sensor and a new coolant temp sensor and still nothing!!! Please help guys (steve)

My o2s do cycle at idle. but not when just crusing! I have a log i can post to help if needed.

Unplug your ECU. That will reset the long term trims to 100%
Hook up you datalogger and start the car. Log the TPS, O2-R, FTO2, ECT, BARO, and Low trim.
When the ECT reaches 86F (91+ cars) the O2 should begin to cycle. Once the ECT reaches 186F the low trim should start to slowly update and move the FT02 closer to swinging around 100%.

Worry about cruising after your sure this part is working.

 

[matt98eclipse]

K thanxs steve!! I will check it out and see what happens. Yesterday i disconnect the negitive termal on the battery and waiting for 10 mins to hook it back up.... Ill try what you said and see what happens. I wont be able to get to it intell tomorrow because i got a little baby girl coming tonight!!!!!

 

[RiceKiller_TSi]

You have a baby being born tonight and you're sweating your fuel trims?

When my trims did like yours it was because I was running too rich. Guess I was waaay off on the tune and the ecu said screw it.

 

[matt98eclipse]

Lol It may not be tonight but here any day. The dsm addiction!!

So if im running to rich it would cause my fuel trim to not change??

 

[RiceKiller_TSi]

Well, yeah. It seems that the tolerances were definetely out of range before I fiddle farted around with the MAFT settings and like you I saw 100% all the time on all trims.

Once I leaned it out a bit I noticed after driving a bit that the levels started to change. Make sure you have your MAFT set correctly for the size injectors you have and even if you do then try slowly removing fuel... one click at a time. Like ol boy said you should see if your idle trims change after the o2 warms up too.

 

[RiceKiller_TSi]

Hey, I just noticed in your profile you have a 255. Do you also have an adjustable FPR?
If not you are probably overruning your FPR.
That equals richey rich.

 

[matt98eclipse]

I have a 255 but i didnt install it yet cus i wanna fix this problem first and im waiting to get a afpr!!

If i set the maft to the stock 450's the car dardly even runs cus its so rich.

 

[RiceKiller_TSi]

Yeah, I had the same problem. MAFT is crap to tune with alone. You have to set your maft for smaller injectors just to get it to idle. I ended up getting a DSM Keydiver Chip and it took care of most issues that the MAFT left me struggling with. If you can get a friend (or shop) with a wideband to help you tune it you will get a lot closer to a stock tune.

 

[steve]

If your too far off in either direction the ECU will try to cause the O2 to switch/cycle and give up if it can't.

 

[matt98eclipse]

Weres the cheapest place i can find a new TPS sensor??

 

[need2boostpsi]

sorry to bring this post back from the dead, but i have one question that pertains to this scenario. ok my low middle and high fuel trims are stuck at 100% at idle my o2 reads .03 - .05, and a DTC will come on at idle and go off it you rev it. my only mod is a 2g mas with stock injectors. now my question is will the maf be enough of a lean condition to cause the ecu to give up and the o2 not to cycle. my o2 is new btw.

 

[steve]

sorry to bring this post back from the dead, but i have one question that pertains to this scenario. ok my low middle and high fuel trims are stuck at 100% at idle my o2 reads .03 - .05, and a DTC will come on at idle and go off it you rev it. my only mod is a 2g mas with stock injectors. now my question is will the maf be enough of a lean condition to cause the ecu to give up and the o2 not to cycle. my o2 is new btw.

Yes. The 2G MAF will cause the car to run lean enough to not be able to enter closed loop.

You need something to tune the car with.