Concerning fuel trims

It seems whatever sensor it decides to read after roughly 5 seconds from the normal cold start sequence, that is making my afr spike, and plummet straight down. My stft starts off at 3%, then after a few more seconds, will plummet straight down to -25%. I'm at such a loss, I've spent most of the day going over any unclipped connectors which yielded nothing. I've tested boost leaks, and could not find one. I've reverted back to my original catch can setup (catch can between intake manifold and pcv vacle) and that hasnt changed anything.

What am I missing here? I wanted to assume my maf is bad, but I've got a spare oem from a cx7 (same model number and all) and that doesnt change. MAF has been cleaned possibly 7 times and obd2 readouts from either torquepro or forscan shows the exactly same values, hovers 2.7 g/s which is normal.

I wanted to assume O2 sensors but even that is reading normal from the obd2 (I assume). What the hell is causing my afr to spike, and plummet? I'll look up how to clean the pressure release valve for the fuel pump but my knowledge here is lacking.

 

After bringing it up to temp, this is the color smoke that fills the garage. The black stuff has been from the constant on/off cycles

 

Black exhaust tip on gasoline turbo car with modded/removed cats is generally normal. There's a lot of soot developed from running rich, plus oil from the turbo/PCV setup.

Having a puddle of it on the ground is also relatively normal from condensation in the engine/exhaust cleaning out some of that carbon in there.

As for the pause before the trims tank, that's probably because the primary O2 needs to heat up to read properly (it has a heater wire). You can try unplugging the secondary (I tend to run without one because I had many issues with it plus it fucked with my lean burn tunes). It will be the connector near the primary 02 that only has one plug for the one wire, instead of two plugs merging (which is for the primary; one is sensor and the other is heater, if memory serves).

If your secondary is tanked, I could see it causing this issue.

 

Roger, I'm planning to yoink some used ones from the junkyard off of some cx7's (gotta still lookup if they use the same sensors, but I'm 90% sure they do). Any recommendations on cleaning an o2 sensor before installing? I'm only planning on doing this since I'd like to make sure this is my problem before committing on spending 200+ on brand new ones that I likely can't return if it doesn't solve my problem.

I expected soot, but wasn't expecting that much water. When first starting the car, the room had filled with the same color smoke, although have yet to check my fluids as the car is still hot. I'm sure there's alot of factors here, but had a moment aswell where the car was a no-start, and the solution was to reset the ecu (removed battery terminal, and plugged back in), so I think whatever data it had saved was tampering with the possible extreme fuel trims I was seeing. Coupled with the condensation, I assume got onto the cold o2 sensors, just made things worse.

I had ran the car for a little longer and ltft has turned to -7, and the stft hovering -10. I've been chasing positive fuel trims so much that it has now turned negative, I assume that switching pcv layouts (had a check valved, catch can) might have been the culprit in solving the boost leak but can only know after I test out different o2 sensors and the car levels out on what it wants to do for trims.

I will get back to it tomorrow after I've acquired a couple sensors to test out.

 

Don't replace the secondary o2, just unplug it for now. Worst case, your primary is at fault (unlikely) and it doesn't improve anything. And you get a CEL related to the secondary. It's technically not needed, as I've not run one in years.

 

Started it up this morning somehow, without doing anything, fuel trims are exactly where I want it. Ltft +3% and stft targetting 0% perfectly. Now I've got another issue concerning excess white smoke out the exhaust. Smells like water, I doubt its oil but I'm confused how I even got here now.

My assumption is either failrd pcv valve or failed turbo. Either of those are a definite possibility, turbo has had quite a few miles but normally the symptoms slowly come up, not just instantly puff white smoke like it is now. Any thoughts on what I could do to test either?



I had let it burn for about 10 minutes prior to sending this image, so I'm sure on normal conditions, this would've burnt off

 

Honestly with the number of cold starts and short runs you have done I would expect it to take longer than ten minutes to clear up.

Mine has been sitting a lot lately and it takes ten minutes to start clearing up and it runs fine

 

Yeah I would too, though I had ran it for more than 10 minutes last night with the same results, and this startup I just performed, I was expecting it to smoke much less and return back to normal. Interestingly, there isn't a huge amount of smoke from coldstart, looks about normal, but as car gets up to temp does it really go bad and fill the garage. I did go for a quick 5 min drive aswell with only plume's of white smoke coming out. I did go into boost a little to see if it would burn off, with it only getting worse.

I did check my oil level this morning before starting, so currently just waiting a bit to re-check if there was any significant oil loss. Had it up to the max dot, so whatever shows up will be obvious if I lost anything there. The smoke's color could pass off as a light blue but it's so faint, it could be my eyes failing me, which is why I'm just checking the dipstick and also to be safe before running it for longer.

I'm finding it a bit hard to think if what I did could've killed it, 5 psi I assume is very little and I'm pretty sure pressure's exceed that in the intake, or even crankcase.

 

Oil level is still at the same max position. Waited about 1 hr ish.

 

It's possible you just pushed a bunch of oil past the seals and into the exhaust, which would take a lot longer to burn off.

 

This. You need to let it get hot and run for a while to clear out the exhaust

 

I can get behind that theory, I'll go for a bit lengthy of a drive now that I have the peace of mind that oil isn't being consumed that fast. Wanted to be sure in-case I was running dry. The turbo is old, I already have parts to rebuild the turbo and have been planning for a while; including a 2nd used k04 for me to make the process faster. I'm going to first run this one for a bit to make sure there aren't any outstanding issues before going through with the turbo replacement.

Will let you know what happens next, at least so far it seems my vented catch can might have been the issue with my fuel trims, coupled with me not running the car long enough to let the o2 sensors actually warm up in the middle of my troubleshooting; to let the ecu figure out what it wants to do. Still a little tentative since once this oil is burnt off, I'll observe fuel trims in the event something changes, but if the smoke does burn away, it's time for a new turbo.

 

I went back and looked at the OP for mods, and noticed you have an intake. I forget if it's intake or downpipe that can cause the pressure imbalance within the turbo that makes it more smoky, but having both intake and downpipe fixes the issue, if memory serves.

Someone with more stock turbo knowledge will chime in and correct me if I'm wrong, I'm sure.

 

You guys were right with the oil seals on the turbo being the cause. Went for a drive, and burnt off the oil and now no longer smoking. Popped open the hood to see smoke coming from the exhaust heatshield so I assume turbo. Now that smoking is resolved, seems we're back to the old fuel trims.. from cold start fuel trims were really good at 4% long term, but after the drive we've gotten backwards to square 1.


Could be o2, back when it was a bit smokey it had been only 4% long term and short term was 0%. But maybe it was due to the smoke?

I'm starting to think about just going through turbo replacement even though fuel trims are off. I originally wanted to tackle the trims before replacing, just so I dont add more confusion to troubleshooting, but I'm starting to think I should do it and see what happens.

 

Seems you were right; it was the residual oil from blowing past seals when I pressurized the intake. Just posted an update. My old fuel trims with these mods used to be pretty good from this old reply:

Nothing changed between then and now, so something leaks when the car is hot. Going to confirm that when I cold start the car tonight and observe fuel trims without driving.

 

Another thing that can make the car smoke that bad: I once tried Valvoline oil, which was supposed to be 5w-30 but poured as thin as water. Any time I let the car sit and idle it would start to smoke, but never did while under power.

So add shitty or thin oil to the possible causes here.

 

Everyone always blamed downpipe but it was poor pcv draw on gen 1 at idle

 

Didn't adding an intake fix the downpipe smoking though?

 

Some of the intakes moved the vacuum port closer to the turbo mimicking what Mazda did on gen two to alleviate the problem. Corksport for one moves the port

 

Ahh that makes sense.