Stock ECU fuel trims do not change. Is this ok?

[EagleTalonTim]

ok, i just ran a few logs and noticed nothing has changed since last year. The fuel trims are staying at a steady Low : 113%, Mid : 107%, and High : 105%. They have not changed at all. I already read another post on here that was not quite my issue, but it is close. Here is the link to that post. : http://www.dsmtuners.com/forums/tuning-engine-management/274780-fuel-trims-dont-change.html

My set up consist of a JDM engine with a Cyclone intake, Evo 3 16g, stock 450 injectors and a rewired stock fuel pump in a 93 A/T Talon. The ECU has been replaced with a M/T ECU to compesate the injector size difference in a A/T Talon. The MAF is still stock so I have nothing to tune with.

No matter what I do, the fuel trims never change. What should I do?

 

[JayRolla]

Take the battery terminal off and see if it resets too zero. I have this same issue sometimes and all it takes is taking the negative battery terminal off. I really dont car anymore since I run a lean burn at cruise and trims are off all the time.

 

[EagleTalonTim]

With those trims, should the engine be running rich? Some of my friends say they smell the car running rich when they follow behind me going somewhere.

 

[EagleTalonTim]

ok, I just replaced my t-stat with a 180° t-stat and radiator cap for the winter then took it for a drive. I turn my datalogger on after it warmed up to see if the trims would change but they didn't When I read the other post listed above, it said the coolant temp needed to be 190° before the trims would adjust. Mine never got higher than 145 while driving but the temp gauge was a tad under the middle mark where it usually sits. When I pulled into the driveway, I let it run at idle for about 5 minutes and it warmed up to 192° then the low trim started to change. As soon as I started driving again, it went back to 145°. What should I do to fix this?

 

[Lonnie gandee]

I've never heard that.... I know sometimes it takes a good amount of driving to change them..


Especially if you've already put a bunch of miles on your car since last reseting the ecu..


Do whats been suggested.... Disconnect your battery for a minute.... Then retest..


Why are you looking for them to change anyway?



Your trims are excellent except your lows.... Thats why your friends smell you.... Your rich...

Pull some fuel out at idle.... Should do the trick.

 

[EagleTalonTim]

I am wanting to change them because I only get 18 mpg I am going to try the reset today and see how that does. Hopefully my work will let me do a boost leak test today too. been about a month since my last one.

 

[steve]

Sounds like the thermostat you put in has failed open already.
If it was working correctly it would regulate the temps.

 

[spyderturbo007]

With those trims, should the engine be running rich? Some of my friends say they smell the car running rich when they follow behind me going somewhere.

Yes, it will. Trims over 100% and the ECU is injecting additional fuel leading to a rich condition. Once you take care of the T-Stat problem, see if the trims move back to around the 100% mark, if they do, you're fine. If they don't, I would look at your front O2 sensor. When the sensors get old, the voltage output drops, causing the ECU to see a false lean condition.

In an attempt to compensate for this false lean, the ECU increases the FT's and drops your gas mileage.

 

[EagleTalonTim]

here is the update so far. Nothing has changed with the fuel trims and the coolant temp is still not going higher than 145° while driving. If I sit still for over 5 minutes, the temp goes up to the 190's then drops back down like it should. My O2 reads at the highest .95 and the lowest about .10 I put a new one on about 5 months ago. There is only 1 O2 on my talon. The rear was never there. Do you think I would be safe to build some kind of electrical device to trick the ECU to make it think it the temps are actually higher?


Oh yeah...forgot to add.. I reset the ECU this morning and drove to work and back keeping an eye on the fuel trims. My drive to work is 43 miles one way.

 

[steve]

Do you think I would be safe to build some kind of electrical device to trick the ECU to make it think it the temps are actually higher?

You'll need something like that if the car stays below 186F.

Like I said before, it sounds like your thermostat is currently stuck open since it's not maintaining a steady temp. Stationary the cooling system isn't really doing anything until the coolant gets warm enough to turn the fans on. Once you get some airflow through the radiator your overcooling and the coolant temps plunges.

I'd go get a OEM thermostat for the winter.

1G's only have 1 O2 sensor.

 

[jrohner]

Your trims are excellent except your lows.... Thats why your friends smell you.... Your rich...

Pull some fuel out at idle.... Should do the trick.

The ECU is adjusting for that, so he is not rich at idle. 113% is not too high, it's typical of a 1g; the trim is not close to maxed out.

You will be rich at WOT though unless you have tuned it leaner; they are tuned insanely rich from the factory.

It doesn't matter much if the trims are not constantly updating, once they are set they are set, unless your fuel changes ethanol content or your injectors get dirty. The engine coolant does have to be <188`F for trims to adjust, but not updating is nothing to be alarmed about.

 

[Highbooost]

Alright here is what is going on. For starters when you run a lower tstat in the winter time especially a 180 or less those temps are not going to get high. MY 160 in anything less than 55degrees would not let the engine get past where you are at. Another factor is FMIC, I did NOT have one on the car which cooled it excessivly, and the fluidyne didn't help either.

To answer your original question about fuel trims the factory ECU has to see engine temps over 190 to adjust the trims, check the DSM Link Wiki stuff out. If the values fall under those temps the ecu will not make fuel trim adjustments.

It has been pretty cold in you neck of the woods recently 30's and 40s. I would reccomend the stock tstat for the winters and the 180 from spring to fall. I know it is a pain in the dick, but it is what works BEST.

Hoped that helped. OH yea, if you don't want to change tstat just put some cardboard in front of that radiator that will heat things up.

Later Dr Turbo

 

[pneumo]

Try watching the O2 trim. It should constantly cycle up and down along with the O2 volts when the engine is above 88*F and the car has been running longer than 2 minutes. Check it and let us know what you see.