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Recently replaced etc, pcv hose, and fuel pressure regulator, I've been monitering my trims and after a good several hours when I go to park my bank1 ltft is about 8.4% and bank 2 ltft is at 9.4 at idle.now this was after driving for several hours to monitor the work I have done. When I'm driving with rpms around 2000 I'm seeing pretty consistent trims even zero across the board for short periods. Now I'm wondering if this could be consequence of engine wear or a possible dirty maf sensor or even dirty injectors?
So, engine nicely warm, parked at idle - quite big LTFT trims.
Do they drop if you rev to 2000-2500 range for a few seconds?
If yes, air leak(s).
yes they drop instantly at rev, im starting to suspect i may have put the throttle body manifold gasket in backwards now, or the pcv breather hose i got as a replacement isnt sealing, i do here what sounds like air being drawn into engine just leery of spraying starter fluid around the engine.
Be carefull sparying flammable around engine bay and the ECU is so fast to adjust rpm that you might not detect the difference.
These are quite cheap:eBay Leak tool / Smoke tester
Be carefull sparying flammable around engine bay and the ECU is so fast to adjust rpm that you might not detect the difference.
These are quite cheap:eBay Leak tool / Smoke tester
agreed thanks for the link, as I said I was pretty leery when I was suggested to spray propaine or starter fluid to find the leak. With this smoke kit am I looking for smoke to be drawn in or blown out?
So started up I have cold readings and after readings. Seems my short term is starting excessively high then switches over to high long term at idle. Right on start up Now at idle...
Don't forget also that on cold startup, the fuelling is running open loop while the O2 sensors are heating up & it then switches to closed loop. Open loop runs off a table of values that's programmed from the factory. When it switches to closed loop, the ECM then makes adjustments based on MAF, O2 sensors, etc.
Last edited by User 42324; Mar 1, 2025 at 06:04 PM.
Don't forget also that on cold startup, the fuelling is running open loop while the O2 sensors are heating up & it then switches to closed loop. Open loop runs off a table of values that's programmed from the factory. When it switches to closed loop, the ECM then makes adjustments based on MAF, O2 sensors, etc.
I get that, from everything i can see, im guessing its a leak somewhere. I ran tests on my fuel system and injectors so everything is within spec, what i did notice is my maf readings go through the roof when i accelerate so im thinking my air leak is throttle body or around the intake piping.
I have very similar fuel trim readings on my 2009 XF-S. After a long highway drive - I'll get P0101 codes and a CEL - which will self-resolve after a bit of city driving (several ignition-on cycles).
I have cleaned the MAF's multiple times and seafoamed the intake tract. Car ran much better after that (and it ran fine before that as well) but the CEL issue and trim anomalies persist. I'm pretty sure its a vacuum leak that is only big enough at higher RPM and for longer runs. I bought a smoke tester off of Amazon but it was defective out of the box and I returned it and I haven't bothered ordering another one.
If I have a shop try to track this down - I'll report back on their findings. But for now - it's not enough of a problem to spend time/money on.
I have very similar fuel trim readings on my 2009 XF-S. After a long highway drive - I'll get P0101 codes and a CEL - which will self-resolve after a bit of city driving (several ignition-on cycles).
I have cleaned the MAF's multiple times and seafoamed the intake tract. Car ran much better after that (and it ran fine before that as well) but the CEL issue and trim anomalies persist. I'm pretty sure its a vacuum leak that is only big enough at higher RPM and for longer runs. I bought a smoke tester off of Amazon but it was defective out of the box and I returned it and I haven't bothered ordering another one.
If I have a shop try to track this down - I'll report back on their findings. But for now - it's not enough of a problem to spend time/money on.
Stft and ltft trims
