Issue:
After doing some more data logging the bottom line is my car runs, or is perceived to run lean at idle/off throttle but rich under load/on throttle, even at wide-open throttle, engine hot or cold but the car seems fine and I'm getting no codes relating to fuel trim as both are less than 10%.
Brief info from logs:
I can't attach any extracts so I'll explain it as best as I can
A WOT run in 3rd up to 4K rpms the fuel trim stayed constantly at -2.3% with the cat reaching 984C, cruising at 60 at roughly 3K revs still at -2.3%.
At idle, stationary, the idle fuel trim reaches 8.6% and stays there.
At startup, the idle fuel trim will start at 2.3% then steadily creep up the longer the engine runs.
This is what is throwing me off as it's acting like it's turbocharged and has a boost leak but its NA.
I've put some extra info below in case it's relevant.
-----Extra info-----
Info about the car:
125K miles, AZQ engine (1.2, 3 cyl. 12V), has only been run on Shell V-Power since I've owned it (roughly 2500 miles).
I occasionally get the fault codes P0130 P1103 P0133 typically at 100 miles after being cleared but get P1103 intermittent, pretty consistently but it doesn't turn the engine light on. I have a multimeter and want to test the plug coming from the car but I can't find a wiring diagram or specs for the voltage that I should expect.
When I got the NGK o2 sensor fitted I asked my mechanic to give the harness and the plug a look over and he said that it was all fine.
What work has been done:
I've cleaned the throttle body, however, on the car as it just would not separate from the intake manifold. With it being 18-year old plastic I didn't want to push my luck, so it is not as clean as I would like it to be and it was definitely not happy starting afterward. It now starts fine after a good run. The throttle body was adapted using VCDS after I cleaned it.
I did a service 7 months ago. Manicat was replaced 6 months ago with a non-genuine unit (which I think may have come to bite me in the arse
) I had the fuel filter (MANN with 3 Bar reg) and pre-cat o2 sensor (NGK) replaced 2 months ago. Another oil change was done just over a month ago (MANN filter, Castrol edge 5W-30).What has been checked:
The only vacuum leak I can hear is a very very tiny one coming from the oil filler cap with my ear basically half an inch away from it with the old and new cap. If I open it while running it continues fine but when I put it back on it almost stalls but recovers. PCV fault or expected behavior?
I can't see or feel any cracks in any of the vacuum lines. Evap passes the readiness test but I don't have a clue where it is to give it a visual check.
Brake pedal feels fine. No stiffness at all.
Ignition coils are genuine but dated for 2008, the post-cat o2 sensor has VAG stamps so it's either the original or was replaced with a genuine part but not by myself.
Pulled the plugs and they look fine to me and I have attached pictures.
What I am yet to do:
I have a MAP sensor coming today and will see if that makes any difference.
I haven't checked the timing yet to see if it's jumped on the exhaust side as these engines seem to be known for doing that.