Any ideas? Thanks.

 

Your point? If you don't understand fuel trims, do a search first before asking.

Example (read pdf's) =
https://www.jaguarforums.com/forum/g...z-49317/page2/

In other words 0 = good

 

I know 0 is good, I don't like +10, when it is cold.

 

When adding the long term trim to the short term trim, you obtain a basic “total trim number”. This number should be very close to zero, never exceeding 10% positive or negative. For example, A LTFT of 3% and a STFT of 1% would give a total trim of 4% which is within the normal range. Negative numbers can work in your favor as well; for instance, the STFT is 4% and the LTFT is -2%, the total trim number would be 2% which is near perfect. The same thing if the total trim number wound up in the negative. A number close to zero is fine, but 10% negative or positive is out of limits. Now, besides the total trim value being well below the 10% threshold, the spread between the long term and short term fuel trim values must be as well. As noted above, adding a negative number to a positive number can get you closer to zero which is a good thing, but if the spread is too large, you need to find out why. For example, LTFT is 7% and STFT is -7%, well that would give a total trim number of zero which is “perfect”. However, the spread between the numbers is 14% which exceeds the target “10%”. While it is true the total trim number is zero, it’s a bad way of getting there. It is an indication that the PCM (power train control module) is not in complete control of the fuel injection, it’s scrambling to make up for an issue that is nearly out of its control. If the vehicle utilizes mass air flow (MAF), this condition STRONGLY suggests Mass Air Sensor issues. If the vehicle utilizes MAP (manifold absolute pressure sensor), check the vacuum at the MAP sensor. Suppose that the numbers are all well within the target 10% limits at idle (remember, that doesn’t mean 9% is good, just that the numbers may not have exceeded 10% yet). You should now make certain that there is no fuel starvation issues occurring. Hold the engine RPMs up around 2500 for a minute and observe the trim data once more. (Hint if the numbers don’t change, that would be very suspect. Short term trim will usually be moving all the time, but if your Long term trim doesn’t change from idle to 2500, you need to investigate further.

 

I suspect vacuum leak when engine is cold, which disappears when it is hot.