Long Term fuel trim (newbie)question

[mtnman]

I was going down the road recording data and running the dashboard and I noticed that the LTFT -1 graph was running much higher than the LTFT -2 graph. Is this Normal or should the 2 be closer together (even) for optimal performance?

[mistermike]

Is the car old enough that it might be starting to have little mechanical discrepencies like a dirty injector, exhaust leak, worn plug or wires etc?

[BowlingSS]

I was going down the road recording data and running the dashboard and I noticed that the LTFT -1 graph was running much higher than the LTFT -2 graph. Is this Normal or should the 2 be closer together (even) for optimal performance?

One O2 could be getting weak.

Bill

[dc_justin]

I have a similar situation, but reversed, and only in high vaccum situations (eg, idle and deceleration). I'll see as much as a +15 difference on the LTFT2 value, but only 2-3% difference in less vaccum and boost... Could this be a sign of faulty injector (perhaps it is not staying hot enough??)

I have a 2003 Silverado SS with radix supercharger @6psi, and I've removed and re-installed the blower in attempts to rule out a vaccum leak to no avail...

[dfe1]

A few percent difference in left/right fuel trims are fairly normal, and subject to change without notice. Anything over 6-8% is excessive and is indicative of a problem with the sensors themselves, one or more injectors or the ignition system. Try switching sensors from side to side-- if the high number switches to the other side, the problem is pretty obviously one of the sensors. Otherwise, you'll have to search further. Make sure there aren't vacuum of pressure leaks (in boosted applications).

[mtnman]

Is the car old enough that it might be starting to have little mechanical discrepencies like a dirty injector, exhaust leak, worn plug or wires etc?

It's a 2003 with around 26k miles.

[mtnman]

A few percent difference in left/right fuel trims are fairly normal, and subject to change without notice. Anything over 6-8% is excessive and is indicative of a problem with the sensors themselves, one or more injectors or the ignition system. Try switching sensors from side to side-- if the high number switches to the other side, the problem is pretty obviously one of the sensors. Otherwise, you'll have to search further. Make sure there aren't vacuum of pressure leaks (in boosted applications).

My application isnt boosted. The differences are 0.7 and 2.5 . I'll try switching the sensors.

Thanks

[BowlingSS]

A few percent difference in left/right fuel trims are fairly normal, and subject to change without notice. Anything over 6-8% is excessive and is indicative of a problem with the sensors themselves, one or more injectors or the ignition system. Try switching sensors from side to side-- if the high number switches to the other side, the problem is pretty obviously one of the sensors. Otherwise, you'll have to search further. Make sure there aren't vacuum of pressure leaks (in boosted applications).

My application isnt boosted. The differences are 0.7 and 2.5 . I'll try switching the sensors.

Thanks

That difference is normal That is only a couple of %. Did the difference stay with the O2's?
Bill

[DaleMX]

Mine has big differences too (like + 8 on 1 and -6 on 2), but it is being caused by air leaking into the exhaust system from all the crappy welds I did on the down pipes. I made a make shift repair by using band clamps and it really helped alot.

My 2 cents worth, check for exhaust leaks before the O2's.