Real Time Data: LTFT are higher than normal

[M.RedWS6]

I have been using the U7198 for about 3 months now in my 2000 Pontiac Trans am and have noticed an unussual jump in the long term fuel trims. I can't recall what the fuel trims were when I installed the performance tune to the car but they were not over 15% at idle. I have also see them go as high as 25% when I stop at a traffic light? Any idea what could be going on, any input would be helpful.

Would you know what the LTFT are typically at with the performance tune installed on a stock F-body?

[mikel]

Are these LTFTs positive?
If so, they are a bit out of whack.
Make sure there are no small vacuum leaks anywhere, or a loose connection on the induction side of the motor.
What do the LTFTs look like at cruise and at WOT?

Thanks

[M.RedWS6]

The LTFT are positive and they decrease at partial throttle to below 10% but as soon as I come to a stop and engine idles they come back up? I also noticed that when I allow the vehicle to cruise without a gear(neutral) the RPM's surge and stay at about 2K at 25 MPH and higher with the car in neutral but cruising due to it's momentum.

[mikel]

OK, let me know what they look like at a 55 mph cruise and at WOT.

Thanks

[M.RedWS6]

Mike,
I was not able to get the car to WOT but the closer I got to it the more that the LTFT fell. I think I might have been at about 50% throttle and the LTFT was at about 5.5%, and at 55 MPH the LTFT were 8 to 9 %.

I did notice that one of the o2 sensors in bank1 had erratic readings at idle and cruising speeds(e.i. 730 to 350 to 650 to 95 to 700....), its corresponding o2 sensor in bank2 also displayed the same reading in both conditions. While the other sensor in bank1 remain steady between 650-750 at cruising speeds and idle.

[M.RedWS6]

Mike,
How bad can I damage my car if driven with the LTFT at 25% when at idle. at cruising speeds the LTFT are between 8% and 12.50% depending on the speed?

[mikel]

Not going to hurt anything, just go easy on it until you are able to get the trims dialed in.

Thanks

[M.RedWS6]

Mike,

Could you give me an idea of what the LTFT are suppost to be once you download the "Performance" tune on a 2000 T/A??? I know what I need to get as close as possible to -2 to +2 range, but given that there are not DTC triggered or leaks (intake or vaccuum) in your car what is the range that the Performance tune should put me in? I think that 18.35 % is too high.

As I what monitoring the Real Time Data this is what I noticed:

The LTFT's read as follows at idle ,

before cars warms up
Bank 1: 9.38%
Bank 2: 8.59%
5-10 minutes After
Bank 1: 18.35%
Bank 2: 18.35%
+10 minutes with Hood open
Bank 1: 7.34%
Bank 2: 5.49%

LTFT's at a cruise,

I notice that if a keep it in a certain gear for too long they go higher than +10% depending on the speed. As soon as I change gear they drop briefly to about +6.25% until they get stabalized and start going back up. In some cases they tend to top off at about 15% .

Let me know if you can make anything of the information that I provided to you, thanks for your help!

[06MonteSS]

see the replies to your other post: http://diablosport.com/index.php?name=P ... pic&t=1749

and view the sticky at the top of the Predator GM forum: http://diablosport.com/index.php?name=P ... opic&t=917