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Old 12-09-2016, 06:54 AM   #41
jfoj
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The 2 most important sensors on any of the modern gasoline engines are the MAF (and MAP if the vehicle is equipped) and the Pre-cat O2 sensors.

If the Pre-cat O2 sensors are original, I would suggest they be replaced because they are consumable and need to be replace by 100k miles based on BMW's service interval, but often they soften and get lazy before this time frame.

Might suggest looking into the current DME flash as many of the problems we are dealing with are bad ignition timing Maps that BMW screwed up over a long period on many models over many platforms.

Thanks for the information on the fuel, was unaware that Europe is offering 5% Ethanol. I have not lived there for almost 20 years.
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Old 12-09-2016, 10:02 AM   #42
MTX-4
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Thanks to jfoj again for his valuable comment.

What kind of fuel do you have available in your area?

It's 98 octane fuel with no ethanol.

Is this a 10% Ethanol mix fuel or a 100% gasoline?

It's 100% gasoline.

What is the history on the Pre-cat O2 sensors?

My sensors were original until two weeks ago I replaced them with Bosch 13477. The car has been driven 120,000 km. I am the only owner of the car.

What problem are we trying to correct/resolve here?

Basically trying to get rid of the negative long term fuel trim. I wish to bring back to, at least close to, zero. Other than that I have no specific problem. May be the engine could pull a bit better and consumed a little less fuel. The LTFTs are the main issue to address.

Thanks a lot!
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Old 12-11-2016, 08:43 PM   #43
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Some update on my case.

With both pre-cat O2 sensors replaced, the LTFTs is slowly getting lower and lower. Not completely back to zero or positive, but down from -5/-6 to -0.7/-1.5. It looks promising. I guess the adaptation is still adjusting so hopefully it can get back to normal after a few more drives.

As a bonus, the fuel consumption has gone down too, from 11.x/100km to 9.x/100km. This level of fuel consumption has never been achieved over the 13 years of my ownership with this car. The power output seems smoother too.

Even though the mileage of my car is still short of the recommended replacement interval of 100,000 miles, as advised by jfoj, one is strongly recommended to replace at least the pre-cat o2 sensors given that the car has been around for over 10 years.
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Old 12-11-2016, 08:48 PM   #44
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After this, I have a feeling that both MAF and pre-cat sensors should be replaced together.

A tired MAF with a sensitive O2 sensors or tired O2 sensors with a sensitive MAF is too much for the DME to accommodate.
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Old 12-11-2016, 08:57 PM   #45
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Kind of boils down to the fact that sensors age and degrade and if you want and expect new car performance it is wise to replace the Pre-cat O2 sensors, MAF and fuel pump by year 10.

Cam and crank sensors tend to be more forgiving as they are Hall Effect sensors and they are not typically subject to the dirt and extremes that the MAF and O2 sensors deal with. If you are really hard core, you could replace the cam sensors, but usually you may get an indication that they are getting sloppy with intermittent codes.
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Old 12-11-2016, 09:48 PM   #46
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Thank you jfoj. As per your advises over this useful forum earlier, I've finally replaced all pre-cat O2 sensors, MAF and fuel pump. I did it one by one and have experienced the improvement by replacing each item.

I guess the exhaust cam sensor has been replaced by a technician some years ago as it looked relatively new than the rest of the components in the engine bay. Might have a go at the intake cam sensor later on.

These engines need regular maintenance, but once it is done it is indeed very rewarding.
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Old 12-12-2016, 03:05 AM   #47
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I have ordered two new pre cat o2-sensors over the weekend and will put them in tomorrow, hoping that my fuel consumption goes down a bit, its sitting at 11,x like in MTX-4's case before changing the o2 sensors. car is driving fine after checking the injectors, i think there might have been an injector, that wasn't pushed all the way in. would that cause the effects that i had?
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Old 12-12-2016, 05:10 AM   #48
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Hopefully the new O2 sensors will rectify your problem.
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Old 12-17-2016, 12:42 PM   #49
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Finally found some time to switch out my o2 sensors - which is a fairly easy job to do compared to other parts. Old o2 sensors didn't look too bad, but chaning them was the right thing to do after 140.000 kms (see the picture). Car is driving fine at the moment, but lets see how long this lasts. Lambda values are almost immediately back to -1.5/-0.8... Its not much, but too much i think, so i'm back to zero. Perhaps i'm going to take a look at the maf again and at the plug, perhaps theres a problem.
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Old 01-16-2017, 04:58 AM   #50
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After some driving my problems reappear: the clutch is juttering/jerking while taking off, changing gears will result in jerking. i'm going to try and change the throttle body to another used one, perhaps my tps is sending faulty values (what would normally result in a cel, but perhaps they are just slightly off). resetting the throttle adaption values will get rid of the jerking for a while.

Anout the maf/ negative values: i had a weekend where i drove around 1000kms, at the end my values where at +2.3/+0.8. thats the values that the newer maf was reading lower than the old one, so i switched back to the new one and got a perfect zero at the end of my trip. inner city driving was giving me negative values again, but that lets me think that the new maf is the good one and the old one is reading slightly off values, that fit better to inner city driving. theres got to be a problem, perhaps with the cold start. on cold days with like -5 degrees celsius my rpm arent dropping until driving about 15 to 20 minutes. is that correct or should it drop way before?

Last edited by sebograf; 01-16-2017 at 04:59 AM.
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Old 02-01-2017, 07:31 PM   #51
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Hello from Argenitna guys, this thread is really helpful and fact resolutive.

I've the same problem of negative LTFT on my 328i 1999. I was reseting the adaptations 2 days ago to do new measures and today complete the 120km to store the adaptations again.
This are the reports.
COLD START
https://www.dropbox.com/s/9ofu5gln4c...Start.csv?dl=0
HIGHWAY
https://www.dropbox.com/s/cysi7q8z2x...HGWAY.csv?dl=0
WARM IDLE
https://www.dropbox.com/s/htjw7k77in...0Idle.csv?dl=0
DIAG.REPORT
https://www.dropbox.com/s/uw9is84c85...2-01.html?dl=0

I can't found a reason for why LTFT is negative (-5.x bank1/-3.x bank2). I suppose that my post-cats are fake cose they are always stuck on 0.43V. I asking me if this would be the problem?
I know/read that would be good to replace my pre-cat's cose years do his job, but at the same time, the measures of it seems to be ok, or responsive at list. MAF reading at idle looks good too.

Can someone help me with this? Thanks in advance!

Last edited by POLGOZ; 02-01-2017 at 07:34 PM.
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Old 02-19-2017, 09:46 PM   #52
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I wish to report back that after driving for a few more trips the negative LTFTs are slowly getting back to zero (both banks) and even positive for one particular bank (0.0/0/7).

The DME has a rather complicated algorithm and it takes some time to get the adaptation back to where it should. May be, the new O2 sensors need some time to break in as well.
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Old 02-27-2017, 01:11 PM   #53
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Good to hear mtx, that your ltfts are getting better.

Mine are getting worse and worse and i can't put a finger on it. Yesterday I put the "new" MAF back in, its reading about 3,2 -3,3 g/s air with the aircon off. thats more than the old one but still my ltfts are getting worse (-3,9/-2,3).

I try to understand whats going on:
A negative fuel trim means, that there is more fuel than air in the mixture. So it either has to be a overreporting MAF (so there is less air to burn then what was measured) or too much fuel pressure. My MAF readings are on the low end so it doesn't look like it is overreporting, i think the chance would be bigger that it is underreporting. That leaves the fuel pressure as maybe the no.1 problem. Is that right so far?

I changed the fuel filter (and with it the pressure regulator) some time ago, so normally that should be fine, but i think thats the next step i will look at.

Or perhaps its a electrical issue, that the values the dme gets are a bit off. I tried to recrimp the maf-connector, but i have no idea how to do that. do i have to get the small connector for each wire out of the big connector?

Last edited by sebograf; 02-27-2017 at 01:37 PM.
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Old 02-27-2017, 08:31 PM   #54
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Hi Sebograf

I have to report that my current (new Siemens VDO) MAF is reading 3.2 g/s with AC off, my engine is 2.2L though. So yours looks fine to me. I am quite sure my MAF is not under reporting as the old one threw a code P0102 and once it was replaced there was no more P0102 code. I cannot be sure whether it is over-reporting though as the LTFTs had been negative since then (with the new MAF). And surprisingly the old MAF (with P0102 code) had LTFTs of 0/0.7. It is definitely a tired MAF and was under-reporting. This situation really puzzled me a lot up to now.

My fuel pump and fuel filter are also new. It could be that the combination of new fuel pump, new fuel filter and an over optimistic MAF are causing the negative LTFTs issue. I start to forget about this and drive until some engine code comes up again.
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Old 03-15-2017, 09:05 PM   #55
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Hi Sebograf

I wish to report that my LTFTs have now been getting back to -4/-3 again after some long drives. It is frustrating.

Elbow Grease has just posted a video a few days ago on finding a solution for fixing negative long term fuel trims. I am going to try that this weekend. His finding coincides with what jfoj suggested (MAF connections) earlier. I hope this may ring your bell too.



Let me know how it goes.
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Old 03-16-2017, 03:03 AM   #56
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Thanks for sharing this video mtx!
That was the next point on my list, to check all the plugs and stuff.
I will have a go at it on the weekend with the help of the video.
I will report back if this helps, but i keep my fingers crossed that this is our soloution
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Old 03-18-2017, 04:42 PM   #57
POLGOZ
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Thanks MTX and sebograf for this video. I try this DIY and works! Im still under test, but after a couple of rides one bank came to 0.0 and the other -2,8 after months of negative LTFT's (-7/-3) and investigation.
Note to mention that all the peripherals involved on this posible fail aren't new, so... this method is really magical.
Is my second problem "solved" cleaning contacts on this 328i E46. Time before I has troubles with vanos solenoids (misfire) and cleaning/pulling electric contacts I solve the problem till now.
Replace parts in older cars is more than convenient, but some times, magic tricks are better..
I will update if my second bank rise 0,0 too.
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Old 03-19-2017, 01:37 AM   #58
MTX-4
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It's good to know the trick works in your case too, Polgoz.

It is like a myth that how does the trick work. My personal speculations are :

1) The DME programme is sort of running in a bug mode with the STFTs are running all over the places. I seem to understand the STFTs a bit better now, as STFTs SHOULD switch to a slight richer mixture when idle and low speed to facilitate smoother engine running and prepared for a take off from stationary or low speed. The STFTs should then be running near zero adjustment at medium speed and goto negative when the throttle is lift off or with low engine load. I can now clearly see this from live OBD fusion readings on display now. They were all over the places before with extreme negative fuel trim at idle. This bug mode was probably reset during the battery disconnection.

2) The MAF (or some other components) needs relatively higher current draw and that the imperfect contacts restrict this from happening. A low temp MAF (with insufficient current supply) responds much slower (as the temp needs longer time to achieve) and sort of giving a delayed output which confuses the DME and adjusting the STFTs at the wrong timing.

Anyway, my engine is much happier now and so do I.

Last edited by MTX-4; 03-19-2017 at 01:38 AM.
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Old 03-19-2017, 10:54 AM   #59
POLGOZ
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MTX your speculations have sense. Im my experience, I only disconnect negative battery terminal (not whole battery), I don't know if this vary in some way if we are talking in terms of "reset"
In the las 2 months I disconnect the battery 2 times, reset adaptation one time and disconnect the MAF with the engine ON to reset LTFT numbers one time. Neither of this things change the LTFT negative tendency. The DME bug idea sounds real, but I think... if is in this way and after my several resets and disconnects, why LTFT still failing??
I can add third speculation: Seems like all electrical connectors has been designed with low voltages threshold and the years/corrosion makes lost continuity quality.

and as you say.. engine happier, happy heart
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Old 03-19-2017, 11:12 AM   #60
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Constant thermal cycling can and will cause the female terminals for sensors to loosen up over time.

You need to pay attention when connecting/disconnecting the connectors to see if the female terminals have enough "grab".

Also many aftermarket sensors do not have the same thickness metal male pins or blades, so this can and is another tricky spot to pay attention to.
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Fuel pump failures - http://forum.e46fanatics.com/showthread.php?t=929501

Temp Info - http://forum.e46fanatics.com/showthread.php?t=964491

Hidden OBC Menu - Check Voltage, Temp, Fuel Level - http://forum.e46fanatics.com/showthread.php?t=239619

E46/E39 GM5 Door Lock Info - www.bmwgm5.com

Lower hose temp switch O-ring - BMW #13621743299
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