MK2 focus fuel trim confusion

[cerulean haven]

On cold start, I get -7 (ish) STFT, it idle pretty rough, feels normal idling in drive and while driving, but you can still feel it a little rough when cold idling in park and drive.

LTFT consistently sits at 6-7% (positive), no changes which is odd since when cold, stft is -7%.

Basically once the car is warm it idles like a brand new car, stft is 0, but ltft is still somehow 5,6,or 7 percent positive... IDLES slightly rough cold, great when warm, no concerns actually driving.

I am thinking upstream o2 sensor at this point, although spark plugs do look slightly fouled AROUND (not on) the center electrode, and smell slightly burnt (possibly wrong heat range plug, unsure tho)

[signal grove]

Long term takes forever to change

[cerulean haven]

so what u thinkin it could be @signal grove

[signal grove]

On cold start do you mean before or after about 2 minutes, some o2 sensors read bullshit before then

[cerulean haven]

well its in open loop for about 30 some seconds and then goes into closed, its happening before and during closed

unless im a restard

[signal grove]

Ignore open its no longer new and perfectly operating, it doesn't use the o2 sensors then

Adding fuel I would say you have an air leak but negative is interesting

[cerulean haven]

so if i am wrong and its only happening in open then im probably looking at a fuel concern since sensors (maf, map) are reading fine

the weird thing is that ltft is always positive, never changes really but short term is around -7 cold just idling, havent checked driving but around 0 warm idle

[signal grove]

Any exhaust leaks?

[cerulean haven]

na its super quiet

[signal grove]

Might have a bad seal somewhere that expands enough to work when hot

[cerulean haven]

if i had an intake leak wouldnt it be more lean than rich

[halcyon summit]

GG @cerulean haven, you just advanced to level 6! Chat more to level up and earn top roles!

[cerulean haven]

on startup

[signal grove]

Yes

Unless it's in the exhaust and before the o2, then it goes rich

[cerulean haven]

im just confused, my stft never shows +7 while driving or idling, not sure where ltft is getting that

[signal grove]

Does it burn oil and hows the crankcase breather?

Long term can take hundreds of miles to fix

[cerulean haven]

well from day to day it will fluctuate from 5-7, a few days ago it dipped to 3

but ya no oil burnt, just pulled plugs and no oil in the cylinder on any and no drops in oil level since i changed it 3500 miles ago (yes im doing it again soon lol)

[signal grove]

Are the fuel trims about the same on both sensor 1 bank 1 and sensor 1 bank 2?

[cerulean haven]

its just an inline 4 so i only have 1 bank to read off of

[signal grove]

Duh, sometimes I'm dumb

[cerulean haven]

but upstream fluctuates rich and lean from what i can tell and downstream sits at 650ish

i think that reading is mV btw

[cerulean haven]

u and me both brother lol

[signal grove]

Good to know upstream works, if it was constant that's bad

[cerulean haven]

ya ill have to check tomorrow when i drive it but ill make sure its not being lazy and taking forever to cycle rich to lean and lean to rich

[signal grove]

If you do a lot of short trips go out and really stomp on it

You would be amazed at how much that fixes

[cerulean haven]

my drive to work is like 20 minutes, im guessing the mota gets hot enough during that but what u think

[signal grove]

Yeah

[cerulean haven]

hmmm what u think i should do from here

its not like shaking the car but im a perfectionist, ive taken care of this car and want her to last so idk what else to do. The plugs do smell a little burnt almost, wondering if i got the wrong heat range plug or something, 6% is defintely not lean enough to cause cyl temp to get too hot right?

[signal grove]

@cerulean haven

[cerulean haven]

why hello there

hmmm let me read this shit

[cerulean haven]

ok so i actually have a mark 2 focus and for me I had something similar, these cars have a cylinder head temperature sensor instead of an engine coolant temp sensor. The valve cover gasket spark plug well seals commonly leak and that will actually fuck over the CHT sensor, ur gonna get weird readings for your temp on the gauge cluster as well. Its a possibility bc that fixed mine

basically go look up a video how to test it, pretty simple using a multimeter or if theres oil on the connector replace it, otherwise i would just monitor your fuel trims more closely and try to see whats actually going on, plugs arent gonna cause trims to change most of the time so play it by ear, assuming compression and everything mechanical is good, check injectors, etc

hm ok

[signal grove]

Ah yes ford trying new shit and failing ...again

[cerulean haven]

ill try to look at it tomorrow but i did replace the valve cover gasket because it was leaking oil

[cerulean haven]

bro im telling ya, the injectors on these ecoboost engines are DOGSHIT lmao

[cerulean haven]

ya dude its weird but shit happens so check it out

[signal grove]

So is the oiling, saw one lose pressure for some fucking reason, blow the engine and both turbos, it had oil in it

[cerulean haven]

dude i think its the 1.0 thats driven by a WET oil pump drive belt, yes a rubber belt sitting in oil

its insane how dumb they are these days, its disintigrates and clogs the pickup tube and the motor gets no oil lmao