XK8 / XKR ( X100 ) 1996 - 2006

Mystery in need of solving

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Old Sep 20, 2019 | 03:29 PM
  #41  
Berglmir's Avatar
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I was looking at my OBD Data on Fuel Trims and as I have said before, with installing the new purge valve the LTFT have gone up.
However, these high levels only show at idle, so here´s the 100 Dollars Question: What would tell the ECU in IDLE to pump more fuel to the system than under load?
Curious and Curiouser
 
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Old Sep 23, 2019 | 08:09 AM
  #42  
fmertz's Avatar
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Originally Posted by Berglmir
What would tell the ECU in IDLE to pump more fuel to the system than under load?
Fuel trims are adjustments to the base, fixed, pre-programmed fuel table. That base fuel table for sure instructs the ECU to adjust the injectors duty cycles upwards for a higher load and rpm. Trims are closed loop adjustments to the base table, and these adjustments are also tables indexed by load and rpm. In a perfect setup, trims are normally near zero throughout the range of load and rpm.

If you have basic air leaks, they are usually best seen at idle because there is high vacuum and the leaks are likely a high percentage of the low air flow going in. At high rpm, the high air flow may mask the air leaks.

Have you tried a smoke test through the exhaust? This would detect exhaust gasket leaks, as well as leaks in the EGR tube (pretty common) if you have one.
 
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