OtherCarASaab

Where's the fuel filter located on my '06 Yukon XL?
It's he 5.3 Flex Fuel ('Z') engine, if that makes a difference...

I'm trying to swap out anything maintenance I can think of while trying to help fix an apparent misfire condition.

I've read somewhere that '05 and newer the filter is part of the pump assembly on the trucks, but it's available as a separate assembly that claims it's an 'exact fit' on one of the major car-part store websites...

MDTAHOE

Most likely it is "not serviceable ". More than likely it is part of the pump. I would have to look it up to be a 100%

OtherCarASaab

At this point, I'd consider servicing it even if it is part of the pump.
I've still got a misfire after doing a bunch of work (wires, plugs, coil pack, intake manifold and gasket), so guessing it's either fuel pressure/clog or engine internal. Not a great intro to picking up my first suburban, only had it 4 months and also already had transmission rebuilt

Anyone have further info on what the smallest servicable assembly would be? IE filter, filter and check valve, full pump etc... I'd take whatever the smallest part is I could buy and look at it from there. (obviously if it's an $800 part, I'm gonna think pretty hard before doing this as a 'swap it to check' part, but I'm open to suggestions at this point)

Thanks!
Nick

73shark

I believe the fuel pump and filter are a one piece assembly, not serviceable separately.

spyncycle

The fuel filter is supposed to be a lifetime part, never needs replacing as routine maintenance. If you're going to replace the filter, then I would recommend replacing the fuel pump also. No sense in doing all the work of dropping the tank and not replacing it.

tech2

Why don't you check for low fuel pressure or fuel trim data, lack of power...evidence of a fuel pressure problem. guessing at part replacement is a bad way to spend money.

I'd be isolating the misfire to a specific cylinder. compression test if your sure your coil, wire and plugs are ruled out.

MDTAHOE

I can promise you the non serviceable filter is not causing your misfire.

OtherCarASaab

Fuel pressure and testing to see if fuel is part of the issue:
I am trying to learn as I go... on prior cars I'd changed just a filter, as a maintenance thing (i hold cars ~200k miles from new, I often buy with 100k+), so it seemed like a logical place to look.

Ok, for checking for fuel pressure - I had done a non-running fuel pressure test (key on, key off, hold for 5 minutes to see if leak in system), and it passed, it held ~55psi for 5 minutes (with flex fuel, sounded like this is sufficient)... I did not do an engine-running test.
My next question for those far more knowledgible than me, what can the fuel trim tell you? I had been running +/-5% on both short term and long term fuel trims, but recently noticed my LT fuel trim moving up, just the other day, looked close to 15% on both banks.
What does this mean? And what rate of fuel trim adjustment (25%?) is indicative of a true problem - ie when do those vales mean something needs to be fixed, as opposed to just watched?

Thanks again, learning lot from the crew out here!

tech2

a fuel delivery problem generally is worse under high fuel demand. Is that when your problem is occuring?


Testing your fuel pump at idle and fuel trim under no load conditions won't show much.

To make sure your not going down the wrong road; describe your symptoms...what do you see, feel, hear...not what you think the problem is.
list exactly what you have changed.

OtherCarASaab

Tech2,
Thanks for your help. I started a post a few weeks ago describing everything with my first post, and scared people off - no response with 200+ views, so I was going for a narrower question/answer with this post to get some responses

Misfire, through all rev range, 'feel' it at idle with rough idle, but 'see' it throughout the entire rev range by watching O2 sensor readings jump around. Does not go away after engine is warm... I drove for 3 hours straight on the highway, stopped at off-ramp getting off, rough idle and misfire still there.
I've swapped the following parts: plugs (OE delco iridium), wires, serpentine belt, air filter, coil pack 1 (got p0301 misfire 1 code a few times), intake manifold and gasket (stumbled with 'smoke test'), injector cleaner fuel treatment (twice, shop redid after still stumbling first time), evap vent valve (gas cap code gone now, expect unrelated).
Also performed engine-off fuel pressure test to check for leaky injector, no problem there, held 55PSI for 5 minutes after key off... did NOT try engine-on fuel pressure test, I did this test solo in AutoZone parking lot renting the pressure gauge. Shop swapped injectors 1 and 2, no change, swapped back.
I thought possibly fuel issue since I'm almost always getting P0300, random cylinder misfire, and was having a hard time isolating to a single cylinder. I do not feel it is worse specifically at higher demand, no bucking or anything on the highway, just what feels like a 'near constant' misfire.
I figure I've been driving it this way long enough, I'm getting close to having to replace Catalytic Converters now as well when I fix the issue, but before I do that, I want to fix the issue, so I don't swap them twice!

An insights are always appreciated.
It's at a well-trusted mechanic that a buddy recommended today, we'll see what he comes up with (different mechanic than did intake)