PCM Diagnostics & Tuning HP Tuners | Holley | Diablo

Variance in LTFT's between trips. Why?

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Old May 8, 2008 | 10:48 PM
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Default Variance in LTFT's between trips. Why?

Car is a 2002 T/A with a 408ci LQ9 Iron block, MS3, T56, Longtubes, Fast 90/90, from Texas Speed. Tuned by professional tuner and it runs OK.

It was a while since I checked how the car was running after it was tuned, so I did a couple back-to-back data logs after warming up the car while driving around town running errands. Going to the last store I scanned on my way there, and then scanned a second time while returning back home. I was at the store only 5 minutes.

Log A shows LTFT's with inconsistent values in adjacent cells. Log B shows LTFT more consistent cell-to-cell, but very lean. If you compare some cells between logs, you'll see the trims are very different between logs. The driving pattern, traffic conditions, air temp was exactly the same because Log A is going to the store, Log B is returning from the store with only 5 minutes in between.

Why are the trims so different between the logs??
Attached Thumbnails Variance in LTFT's between trips. Why?-ltft_a.jpg   Variance in LTFT's between trips. Why?-ltft_b.jpg  
Attached Files
File Type: hpt
File Type: hpl
LOG-A.hpl (182.7 KB, 61 views)
File Type: hpl
LOG-B.hpl (120.5 KB, 68 views)
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Old May 9, 2008 | 10:47 PM
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Just a guess but, vacuum or exaust leak.
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Old May 9, 2008 | 11:10 PM
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LTFTs are supposed to be in same in large cells. Don't different in each.
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