Yet another lean code/fuel trim adventure

[Bob1035]

Working on getting my newish to me "well maintained" ZHP up to snuff, and currently chasing down lean codes and misfires, and trying to figure out if I need to go in the fuel direction or vacuum leak/intake direction. Main symptoms are persistent lean codes, and misc cylinder misfires that happen at WOT north of 4000rpms.

FWIW, coils, plugs are new new under my ownership. MAF, upper intake boot, misc vac lines, bank 2 cat, and DISA 0 ring were replaced under previous administrations. I've searched around here, E46fanatics, etc, and am still having trouble getting my head around this.

I watched a couple of 50skid videos regarding fuel trims, and here are my results (using a Foxwell NT510)



This is the first time I've dealt with attempting to diagnose with fuel trims. Any advice here would be appreciated! The car is a basket case at this point, so I'm looking forward to getting it running properly.


:cheers

38674

[Pilot05]

I would suggest you look into OBDFusion and lean codes on the E46fanatics site, get OBDfusion, run logs as described and post them on E46fanatics.
Read JFOJ's excellent write-up(s) on the topic.

A point in time (2 in your case) is not that illuminating. You really want to see how signals and inputs change over a range of conditions and time periods.

However some thoughts

I tend focus on long term fuel trims and not so much short term trims. Your long-terms at idle are a little lean, but still under +10..
Since you have one LT trim negative at 3k RPM, any chance your front or rear O2 sensors are switched ? unplug one and see if correct one stops reporting.

Is the MAF a Genuine BMW MAF or Siemens ? It should be.

A smoke test is always a good idea

I recently had negative fuel trims of -10% (Rich) or so on both banks and it turned out to be a faulty (new) fuel regulator that was putting out 60 PSI at the rail

[Bob1035]

Thanks for the input!

[Bob1035]

FWIW, I bought a smoke testing kit, will update when I actually get to use it

[danewilson77]

Make sure the pescy "F" connector is fresh along with all hosing to the fuel filter under drivers side door.

[Bob1035]

Spot on. I finally got around to using the smoke tester, and the lower intake boot area is swiss cheese. Will tackle that next.

[Bob1035]

Way later, but the lower intake boot (and CCV, F connector) replaced this past weekend. Lean codes are gone. I have rebuilt injectors and a new fuel filter ready to go in, so those will be next. Adventures in 18 year old cars, I love it!

[Bob1035]

way way later, new injectors are in, fuel filter is good to go. I actually dropped the car off at a decent indy shop while I was on vacation. Turns out I have a clogged cat causing the issue(s). A set of headers are inbound, and I'm less than an hour from Kassel, so probably a tune from them as well. Going to hopefully put a little life back into this old dog!

[thebeedubya]

I fought an an issue on a 325i, whereas the vacuum leak was coming from a brand new MAF. Where the sensor welds to the housing the weld wasn't solid and was just leaking enough air to cause CEL to come on. I fought that issue for a month until I turned the smoke way up and just watched. you're 100% right, fun with old cars.

[Pilot05]

way way later, new injectors are in, fuel filter is good to go. I actually dropped the car off at a decent indy shop while I was on vacation. Turns out I have a clogged cat causing the issue(s). A set of headers are inbound, and I'm less than an hour from Kassel, so probably a tune from them as well. Going to hopefully put a little life back into this old dog!

so who gets to sell the clogged CATs? you or the indy shop? they might be worth $500

[Bob1035]

I will, if they get sold. I just had them diagnose it, not repair. I might keep them for them time being, even though practically speaking they are useless.