what can cause my fuel trims not to move?

[dnhieu]

okay this has been an on going problem for awhile. no matter what changes i make towards my maft i cant get my fuel trims to move. i have tried a new thermostat with no luck. i have also diconnected my battery a number of times with them going to 100% then back to what they were before. im just curious on what else i can check to start to get my fuel trims to start moving again. also what kind of affects will my car have towards tuning off knock and timing advance if my fuel trims arent moving?

thanks tuners
david

 

[94Jettameowpsst]

Usually the cause of fuel trims not moving is a dead or dying o2 sensor. Check that and get back to us.

 

[dnhieu]

oOops im sorry i didnt mention that my o2 sensor is always cycling back in forth from .2 to .8. i have another o2 sensor i will swap that in and see if that helps. i just got to drive around with my new thermostat and my logings tell me that it is now definetly getting up to temp. the guage never moves from the middle now. i herd that coolant temps on the overflow bottle and the radiator can also affect fuel trims. is this true?


thanks
david

 

[steve]

I just got to drive around with my new thermostat and my logs tell me that it is now definitely getting up to temp. I heard that coolant temps on the overflow bottle and the radiator can also affect fuel trims. is this true?

If you are logging ECT and it's running around 200F then that's the only coolant sensor the ECU looks at. The the dash gauge is not connected to the sensor that the ECU uses.

What are you fuel trims?

Steve

 

[dnhieu]

If you are logging ECT and it's running around 200F then that's the only coolant sensor the ECU looks at. The the dash gauge is not connected to the sensor that the ECU uses.

What are you fuel trims?

Steve

My current fuel trims are FTRL 121% FTRM 92.9% FTRH 98.4%. i just reseted my battery but im sure the fuel trim middle and high will find their way to the richest limit of 81%. when you say ECT im assuming you mean engine coolant temp and they are right at 98.7c which im assuming is a little higher then 200 degrees since 88c is 195f.

thank you for helping me find out my fuel trim problem
david

 

[94Jettameowpsst]

I personally dont look at fuel trims since i have a 1g. In closed loop, you can just feel wether or not your rich or lean, plus logging knock really helps too considering if your not knocking at part throttle boost then you still have room to lean it out. On top of that, idk if its just me, but i had a hard time getting my fuel trims right with just the maf-t so, its alll up to what you want to do.

 

[dnhieu]

i personally do not like tuning off fuel trims eather. i think their good to get where you need to be to make a wot pull but thats it. i would rather tune off knock and timing but since my knock comes and goes as it pleases its hard to make a good wot in 3rd gear. i did twice, and twice i had to let off because somone was comming up rather quickly. also no one has answered my question if your fuel trims have anything to do with the way your knock and timing advance affect, or the way your car is affected for that matter!

thanks alot for the help tuners
david

 

[steve]

Adjusting setting to get the closed loop fuel trims right, isn't tuning.

What your doing it calibrating the parts to get the ECU to the point where what it thinks the correct fuel ratios should be match up with the O2 feedback. Once the sensors and ECU are doing the right things the actual tuning process goes much smoother and you don't have issues with the transition from closed to open loop or part throttle.

If your low trim is saying the ECU is adding fuel (>100%) and the mid and high as saying the ECU is removing fuel (<100) and you have stock injectors then you likely have a vacuum/boost leak. Under vacuum you'll be pulling in unmetered air causing the feedback to be lean and under boost you'll be loosing metered air causing the feedback to be rich.

If you have upgraded injectors and sure you have no boost leaks, then the same data would imply that the injector correction setting are too small and that your injectors have more deadtime than is corrected for.

Steve

 

[dnhieu]

Adjusting setting to get the closed loop fuel trims right, isn't tuning.

What your doing it calibrating the parts to get the ECU to the point where what it thinks the correct fuel ratios should be match up with the O2 feedback. Once the sensors and ECU are doing the right things the actual tuning process goes much smoother and you don't have issues with the transition from closed to open loop or part throttle.

If your low trim is saying the ECU is adding fuel (>100%) and the mid and high as saying the ECU is removing fuel (<100) and you have stock injectors then you likely have a vacuum/boost leak. Under vacuum you'll be pulling in unmetered air causing the feedback to be lean and under boost you'll be loosing metered air causing the feedback to be rich.

If you have upgraded injectors and sure you have no boost leaks, then the same data would imply that the injector correction setting are too small and that your injectors have more deadtime than is corrected for.

Steve

steve thanks for the help and im sorry i havent been able to get back to you on this thread because i was unable to get on tuners all day yesterday for some unknown reason.

so your saying since im running stock injectors that i have a boost leak??? i boost leak my car at least once a week and i have a tiny boost leak between the throttle body and throttle body elbow. other then that the car holds 20psi for well over the 30 seconds. on the other note my fuel trims have changed just as i expected with me not modifying my maf-t settings at all. they changed to low 103%, med 85.9%, and high 81.2%. the low will change all the time tho. from anywhere from 122% to 90%. the low is just all over the damn place.

thanks for the help
david