Fuel trim problem

[LTUDSM]

hey fellas, ive been trying to adjust my ft for past couple of days,and i just can't get them to where they should be. I was following the demo on the ecmlink web,but i got no luck . would anybody give me any advices of what could be wrong,of adjusting the fuel trims?

 

[twdorris]

I was following the demo on the ecmlink web,but i got no luck

That's mainly because something with your car is changing the A/F ratio outside the ECU's control. You can see this in your log file by looking for areas where the ECU was asking for the same A/F ratio in two different places but getting two different results. This will be nearly impossible for the ECU to resolve.

For example, around 19.3 seconds, you had an average A/F ratio of 11.2:1 (AFXWB) while the ECU thought it was targeting 16.1:1 (AFRatioEst). But later, around 34.2 second, the ECU was trying for 15.9:1 (nearly the same) but actually getting 16:1 (and probably even leaner than that because the AFXWB reading was flatlined at that point).

That's a huge difference and it's going to be REALLY hard to get predictable results from unpredictable behavior.

I wish I could tell you what was causing the fluctuation, but I just can't tell that from a log file.

EDIT: One thing you can try is to lock the ECU in open loop mode (Misc tab). When running open loop, the ECU is going to try to maintain a relatively constant A/F ratio. Then you can watch AFXWB to see when the mixture starts changing to see if you can pick up on a possible cause.

Thomas Dorris

 

[gofer]

Damn, if Tom doesn't know the answer then your in trouble.

I'd say start from the basics and check for vacuum leaks around the TB/IM area. I also don't see a AFPR in your modifications list even though your running a Walbro 255 fuel pump. Replace your fpr with an adjustable one and see if your FT's don't line up, it seems that maybe your fpr is trying to regulate flow but its getting overrun.

 

[LTUDSM]

That's mainly because something with your car is changing the A/F ratio outside the ECU's control. You can see this in your log file by looking for areas where the ECU was asking for the same A/F ratio in two different places but getting two different results. This will be nearly impossible for the ECU to resolve.

For example, around 19.3 seconds, you had an average A/F ratio of 11.2:1 (AFXWB) while the ECU thought it was targeting 16.1:1 (AFRatioEst). But later, around 34.2 second, the ECU was trying for 15.9:1 (nearly the same) but actually getting 16:1 (and probably even leaner than that because the AFXWB reading was flatlined at that point).

That's a huge difference and it's going to be REALLY hard to get predictable results from unpredictable behavior.

I wish I could tell you what was causing the fluctuation, but I just can't tell that from a log file.

Thomas Dorris

could it be base fuel pressure out of adjustment? or bad injectors?

 

[twdorris]

I just added an edit above regarding locking the ECU in open loop mode. Give that a shot and see if you can pick up on what might be changing with the engine's operation that coincides with the changes to A/F ratio.

Thomas Dorris

 

[LTUDSM]

Damn, if Tom doesn't know the answer then your in trouble.

I'd say start from the basics and check for vacuum leaks around the TB/IM area. I also don't see a AFPR in your modifications list even though your running a Walbro 255 fuel pump. Replace your fpr with an adjustable one and see if your FT's don't line up, it seems that maybe your fpr is trying to regulate flow but its getting overrun.

ooops my profile wasn't updated for a while I got an afpr with the pressure set to 43.5 psi

 

[LTUDSM]

I just added an edit above regarding locking the ECU in open loop mode. Give that a shot and see if you can pick up on what might be changing with the engine's operation that coincides with the changes to A/F ratio.

Thomas Dorris

i just looked at my voltage ,and i saw ,that it was dropping down to 12.6v while idling,and at that point my ft were getting mad out off of adjustment..... could it be low voltage problem/?

 

[gofer]

Thats another possiblity as well, your alternator might be on its way out...

 

[LTUDSM]

Thats another possiblity as well, your alternator might be on its way out...

new alternator,i just changed. But i got my battery relocated to the trunk,and from my understanding if long cables are used for a power,the amperage is being discharged through the length of the wire right? if so ,then to fix that problem is to get a Higher amperage alternator (Saturn's or GVR-4)

 

[gofer]

new alternator,i just changed. But i got my battery relocated to the trunk,and from my understanding if long cables are used for a power,the amperage is being discharged through the length of the wire right? if so ,then to fix that problem is to get a Higher amperage alternator (Saturn's or GVR-4)

'97 Galant A/T alternator to be exact, if you want a direct bolt/plug in and its 90A.

Instead of rewiring the fuel pump to the battery run the 12v power cable from your fuel pump to the alternator terminal itself using a 10ga. wire.

 

[LTUDSM]

'97 Galant A/T alternator to be exact, if you want a direct bolt/plug in and its 90A.

Instead of rewiring the fuel pump to the battery run the 12v power cable from your fuel pump to the alternator terminal itself using a 10ga. wire.

ill do my battery related things now,and then will check back with the ft.....

 

[LTUDSM]

ok i made a new log today,tell me how does it look like?

 

[snowborder714]

You want to check the "Lock rear o2 voltage" box since you're using that input for the wideband. I'm not sure if that'll do anything to help solve your problem though.

As for fuel trim problems, I'm not sure what to suggest.

 

[LTUDSM]

But the fuel trim at idle is good now right? Brian ,If you would look at my irst log, and the last one ,im sure you would know,what im talking bout