Pretty sure I know the answer here from my previous searching. Appreciate any insight or feedback.

Would like to get a basic tune, mostly for fan control, omp etc. however want to make sure there are no diagnostic issues before I go down that rabbit hole. No running or driving issues, but since I have owned it, this is typical for the Ltft.




So I have chased vacuum leaks with carb cleaner, propane, water etc. Nothing definitive. My next step would be to buy/build a smoke machine and try that. Or just pull the uim, replace the gaskets and inspect hoses and maybe replace the vacuum valves while I am at it. So my questions..

How aggressively would you peruse the cause of high ltft, and at what point do you just let I go?

What are the chances the cause is NOT a vacuum leak?


Only other symptom is high (but not out of range) fuel dilution in the last uoa. Compression was just checked and good, ignition new, cat new, etc, etc etc.

 

Do you have an aftermarket intake?
7.8 LTFT isn't bad.
IIRC LTFT has a +-21% range.
Normal driving conditions like altitude and weather changes can alter the LTFT.
Your screen shot indicates 7.8 at idle it looks like.
You'll likely see the LTFT change as you drive through the rpm range.

 

Your MAF rate is low for the rpm, and the computer think it consistently needs to add fuel, so it's definitely a vacuum leak. Unmetered air is getting in somewhere which is not the intake (except if you have a garbage intake that can't give the MAF steady air). It's within a range that the computer can compensate for, so the real question is whether you care enough to find the leak and zero out the LTFT or if you care that the car basically runs without major issues.

 

There are a few smokers that are relatively cheap. For me I had issues with the line that ran to the primary ports on the bottom outer side of the LIM. It can get cooked by the exhaust manifold fairly easily. Otherwise I had my MAF leak around it and the 3 elbows before the throttlebody.

Might aswell see how your trims change from idle to 4krpm

 

Is there a reason I should care?

Is this costing me performance or reliability? Will it complicate the tuning process? If the answer is yes to any of those, then I care.

 

It's not costing you performance or reliability if it never maxes out the LTFT and gets into ranges where the ECU can no longer compensate for the extra air. As stated above, the max is around +20%. If for some reason your extra airflow is more than 20% higher than what's measured, but the car can only add 20% more fuel, then you're into lean conditions that could be more problematic.

For tuning, it could get in the way, since the numbers you're getting for airflow are no longer the ground truth. Plus the car might need to relearn after tuning, so there will be a period where it doesn't know it needs to compensate at all.