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-   -   P1092 = Lean? Why negative F.Trim? (https://xoutpost.com/bmw-sav-forums/x5-e53-forum/112049-p1092-lean-why-negative-f-trim.html)

Bmwtvboy 06-20-2020 02:05 PM

P1092 = Lean? Why negative F.Trim?
 
Lately, SES comes on and then goes off itself. But past couple of days stays on.
Basic scanner reads: P1092 pre-cat fuel trim system too lean bank 2. (All O2's changed almost 100K ago-Cats orig). But when I read the fuel trims I got a negative. New plugs about 10K miles ago: 4 prong.
1.8 - 3.%. I have many other readings when capturing live data, just don't know how to read them.

1. X starts up perfectly every-time, first time, no lag.
2. MPG's right on schedule, current tank running almost 260 miles half tank.93oct.
3. Acceleration is wonky. Sometimes super sensitive and snappy, other times a little lagging. Tank volume has no influence. Obviously, snappy coming up to running temp. Then not consistent from time to time.
4. NO major oil consumption. But a minor pan leak. Some coolant loss, not sure where or why. Minor suction at idle with oil cap removed. Not intense.
5. It's a really old X, 255K miles. 01. 3.0.
6. Vibration when braking in DRIVE or Reverse at idle, but none at neutral.
Fuel filter/reg is at least 10 years old n 100K miles. Vibration an engine idle issue?
7. Engine, tranny mounts changed 50K miles ago.
Trying not to just throw parts at it. What's a good place to start?
I am going to do basics: Clean air intake system, TB. Check for vacuum leaks.

Thanks.
J

EODguy 06-20-2020 02:12 PM

Minor coolant leak is probably the transmission cooler O-rings.

Ask me how I know [emoji28]

How are your guibos?
Harmonic balancer? (probably not it) but I think the 3.0 had more issues there than others


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80stech 06-20-2020 02:18 PM

Anything that can leak air into the crankcase (eg. rear main seal) can have an effect on fuel trims. Having the gas tank empty or full makes a difference as well and can use up some of the normal operational window of the fuel management.

Bmwtvboy 06-20-2020 02:20 PM

Ouch, did you say leak at R.M.seal? Yeah, last time I did cleaning /oil change I noticed slight drip from bell-housing/motor area only. Park on forward incline and no more leaking. Guess it's not worth the tear down fix. Good to know.

Bmwtvboy 06-20-2020 02:22 PM

EODguy, yikes, that looks a possibility , how serious a tear down repair is that? I'm in FL, running out of cool days in the garage to work on the X. I imagine it means draining the tranny fluid?

Overboost 06-20-2020 02:29 PM

Remember the OPG will leak and run down the back of the pan and come out right where the rear main seal is. I would advise taking a flashlight and looking real good through the access holes underneath and look at the torque converter and plate. If it is dry on the back side, the OPG leak is coming out by the rear main seal.

At 255K, I can assure you that a OPG is needed on the X5 with an M54. This is what mine looked like at 180K.

https://xoutpost.com/attachments/x5-...517_184033.jpg

80stech 06-20-2020 02:32 PM

As much as I hate to recommend it, Kleen flow or any other good brand of engine stop leak can be really effective for the rear main seal and even to soften up the Vanos seals .

Bmwtvboy 06-20-2020 04:50 PM

Is Kleen flow the best bet? Particulate matter seals when heated? Or is it all chemical sealant. I checked OPG closely last time I had her up level for tranny fluid check. Set for one plus days. Everything around pan was wiped clean, only drips; R.M.seal area between B.housing and engine. I don't think at this age n mileage it's worth tearing into this X without a lift, assistance and extra cash. Probably just DitG.

80stech 06-20-2020 06:06 PM

You can't go wrong with the Kleen flo if it is available to you. It takes some time to work as it chemically softens/swells the rubber a bit, but it does work. I'm in the same boat you are as I don't have a lift either and really, the pan gasket should be done too, so where do you stop. You should probably put in a can and a half or maybe 2 initially and then 1 with every oil change. If you don't keep up with it though you will notice a spot on the driveway again and your engine light and lean code coming back shortly after.

I also had the oil light slightly flashing at hot idle at times which has been cured with the stop leak softening the Vanos seals and keeping them from bleeding off too much of the oil pressure. I had actually had the Vanos kit ready to install 3 or 4 years ago and then totally forgot about it.

EODguy 06-21-2020 04:55 AM

Quote:

Originally Posted by Bmwtvboy (Post 1186303)
EODguy, yikes, that looks a possibility , how serious a tear down repair is that? I'm in FL, running out of cool days in the garage to work on the X. I imagine it means draining the tranny fluid?

It's not bad at all but I have a 4.8 and tbh it's one of those things where pulling the shroud and keeping (seemed like) every sharp bolt and looms our of the way take the most time, so I'm pretty sure that you'll have a lot more room with a 3.0.

Draining the transmission is NOT necessary, I used a couple of cigarette filters to plug the holes when I swapped my cooler...

Sorry I don't have the o-ring size but I'm sure it's easy to get from a standard o-ring variety pack.

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