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E46 (1999 - 2006)
The fourth generation 3 Series (E46 chassis) was introduced in 1999 and set the standard for engineering and performance during it's years of production including being named to Car & Driver's 10 best list every one of those years! ! -- View the E46 Wiki

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  #1  
Old 07-11-2013, 09:33 AM
jcrodsa jcrodsa is offline
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Unhappy Idle problems related to ECU

Hi guys,

Here is my story: I own a 318i 1999 E46, engine M43. In the last 8 months I have been reading and spending money to solve a very strange problem with the idle and power.
This is what happens: with an old MAF the car idles perfect but runs underpowered, so guess what? I bought a new Bosch MAF ($500 here in my country) and bad news, the car now runs great, but then on every red light it idles rough and stalls, go down to 1000rpm and dies. It doesn't matter if it is cold or warm, the car just doesn't idle as it should. I have tried three different MAFs and the same thing…. with old MAF car idles perfect, with any new or proven good MAF the car stalls.

So you are thinking on an air leak right? May be idle control valve, vanos seals, or PCV breather? Well I have tried everything, and believe me EVERYTHING! Nothing solves the problem. Quick summary: New fuel pump, spark plugs, MAF, vanos seals, leak tests, idle control valve, run it cold, warm, etc. Nothing changes.

The weird thing here is: With new MAF car stalls, with old MAF car idles perfect!! WTF right?!!! I did a voltage check on both MAFs, and the signals are the same, not significant differences on voltages (~0.20 volts) but then the signal on the ECU (computer) tells the car to inject less o more fuel…. something in the computer is going on…. I am not an expert in this matter, so I took the car to a guy who is…. First thing he said: "this is an air leak"….. Yeah right….. Same story…. checked everything, nothing wrong but idle…. Now he is doing a trial an error with both MAFs to understand if my engine computer has gone bad…. Sadly I cannot test another computer since it has to be codified and that is costly. And I don't want to buy a new ECU without having 100% confidence that it is the problem.
If by any chance, someone has seen something like this, please let me know….. I will own you big time!!
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  #2  
Old 07-11-2013, 09:43 AM
jcrodsa jcrodsa is offline
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Before the ECU was reset, the codes i think were:

P1188 Fuel Control

P1189 Fuel Control

The new MAF is a Bosch, and then i tried a proven working MAF from a fiend car and it was an original BMW MAF, both gave rough idle and stalls the car. The old bad MAF gives a f=good idle, but really poor power.
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  #3  
Old 07-11-2013, 11:13 AM
fdriller9 fdriller9 is offline
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Inspect oil separator hose
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  #4  
Old 07-11-2013, 11:29 AM
jcrodsa jcrodsa is offline
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Done,

All possible root causes has been discarded. That wouldn't explain why with old MAF idle is perfect!
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  #5  
Old 07-11-2013, 12:49 PM
fdriller9 fdriller9 is offline
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Are you sure? The lower hose has been known to crack and throw those codes. You need to remove some stuff to see it clearly.
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  #6  
Old 07-11-2013, 02:53 PM
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ahull ahull is offline
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I think you need in-depth diagnosis on this.... a tool that will read fuel trims, etc. e46fanatics probably has more information on this - you can search bimmerfest as well.

Another option might be to remove your ECU and send it to a reputable dealer for testing. As long as you pack it correctly and insure it, you shouldn't have to worry about it being damaged. People ship their ECUs when they get new engine tunes for performance mods and I believe even BMW was shipping ECUs when special software updates could only be performed at special locations.
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DIY MODS: AA Stage I supercharger, Meyle HD FCAs w Powerflex CABs, Bilstein shocks, Meyle HD Rtabs, Angel Eyes, Clear Corners/Markers w/ LEDs, LED tails, ZHP rims, Akebono pads, AUX input
DIY E46 Merit Badges: Sunroof resurrection, CCV, OFHG, VCG w/ VANOS seals, DISA, Cooling Refresh I, steering giubo, window regs, Magnetic Infandibulator (see wiki)
DIY On deck: Rear Diff bushing. UUC SSK, clutch job eventually, Wavetrac LSD
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  #7  
Old 07-11-2013, 02:57 PM
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ahull ahull is offline
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Quote:
Originally Posted by jcrodsa View Post
Done,

All possible root causes has been discarded. That wouldn't explain why with old MAF idle is perfect!
This makes me wonder if your old MAF is dead and you're getting a basic fuel-map performance, but when you plug in the new MAF it is bringing another underlying issue to the surface. How does the car run with the MAF unplugged?
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2003 330i TiAg Sport Pkg ~90k miles
DIY MODS: AA Stage I supercharger, Meyle HD FCAs w Powerflex CABs, Bilstein shocks, Meyle HD Rtabs, Angel Eyes, Clear Corners/Markers w/ LEDs, LED tails, ZHP rims, Akebono pads, AUX input
DIY E46 Merit Badges: Sunroof resurrection, CCV, OFHG, VCG w/ VANOS seals, DISA, Cooling Refresh I, steering giubo, window regs, Magnetic Infandibulator (see wiki)
DIY On deck: Rear Diff bushing. UUC SSK, clutch job eventually, Wavetrac LSD

Last edited by ahull; 07-11-2013 at 02:58 PM.
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  #8  
Old 07-15-2013, 09:42 AM
jcrodsa jcrodsa is offline
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Quick Summary:

I am not getting an codes, i was at some point before changing some hoses and O2 Sensor. Now scan in clean. I took the ECU to a dealer to check it.

If I unplug the old MAF, car stalls, so it means old MAF works on idle, but again car is underpowered.
If i put the new MAF, car runs great, but dies on idle.

Tech Guy did a test with both MAFs, and all signals are equivalente, it seems that internally on ECU something is interpreting bad the requirements. I hope to get the ECU back this week.
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  #9  
Old 07-15-2013, 10:01 AM
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ahull ahull is offline
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On the 6 cylinder cars, my understanding is when you unplug the MAF, it runs *ok* but not great - underpowered and maybe a little choppy on throttle, but does not stall out. That's why I said it seems like the old MAF is dead and the new ones are just highlighting a different problem.

It is not the most technically expert advice but going with what makes sense from my limited knowledge, which may still be somewhat useful. A 318 owner with experience like yours would probably be the most helpful, but I don't see very many 318 owners here.

You did change the fuel filter when you did the pump and sure all hoses back on correctly..... proper pressure at the fuel rail? Fuel starvation does not always throw a code.
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2003 330i TiAg Sport Pkg ~90k miles
DIY MODS: AA Stage I supercharger, Meyle HD FCAs w Powerflex CABs, Bilstein shocks, Meyle HD Rtabs, Angel Eyes, Clear Corners/Markers w/ LEDs, LED tails, ZHP rims, Akebono pads, AUX input
DIY E46 Merit Badges: Sunroof resurrection, CCV, OFHG, VCG w/ VANOS seals, DISA, Cooling Refresh I, steering giubo, window regs, Magnetic Infandibulator (see wiki)
DIY On deck: Rear Diff bushing. UUC SSK, clutch job eventually, Wavetrac LSD
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  #10  
Old 07-15-2013, 11:02 AM
fdriller9 fdriller9 is offline
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Yea your engine should run ok with no maf installed...not the best, but it will run. It should not stall.

Should like a vacuum issue to me.
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  #11  
Old 07-15-2013, 11:45 AM
jcrodsa jcrodsa is offline
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Yes I did check all hoses and fuel supply. Check this: I tried the old MAF in another 318, it works fine on idle just as mine, but runs under powered too. So old MAF is confirmed as malfunctioning. The fuel starvation or vacuum problem sounds like possible root causes, but why then with the New MAF the car runs perfect? I have checked every single possible leak of air, vacuum, fuel, oil. Nothing comes up!
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  #12  
Old 07-15-2013, 02:11 PM
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ahull ahull is offline
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Well, at least you've confirmed the MAF is sketchy which makes more sense. Your problem is only at idle now. Still could be a fuel pressure issue - only enough pressure while on throttle. Any sputters at high rpm?

Throttle body is clean with new gasket? Sure the ICV is plugged in completely?

I'm wondering if maybe your throttle body is staying open a hair too much on idle and letting in too much air and stalling it. Still think you'd get lean codes with too much air at some point. The ICV is supposed to take over air supply once you're off throttle and the TB closes.
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2003 330i TiAg Sport Pkg ~90k miles
DIY MODS: AA Stage I supercharger, Meyle HD FCAs w Powerflex CABs, Bilstein shocks, Meyle HD Rtabs, Angel Eyes, Clear Corners/Markers w/ LEDs, LED tails, ZHP rims, Akebono pads, AUX input
DIY E46 Merit Badges: Sunroof resurrection, CCV, OFHG, VCG w/ VANOS seals, DISA, Cooling Refresh I, steering giubo, window regs, Magnetic Infandibulator (see wiki)
DIY On deck: Rear Diff bushing. UUC SSK, clutch job eventually, Wavetrac LSD

Last edited by ahull; 07-15-2013 at 02:15 PM.
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  #13  
Old 07-26-2013, 11:38 AM
jcrodsa jcrodsa is offline
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Hi Guys,

So I received the computer back. No problems were found, they reset the computer and check every single port, pin, connector, etc.

We reinstalled the computer and the same problem:

With OLD MAF the idle is perfect, but the acceleration is poor, low response and power.
With NEW MAF the car stalls, no idle, but the acceleration is perfect and good power.

If you un plug the MAF, the idle is poor but does not stalls, this with both MAFs.

We tried the two MAFs in another car and they work fine, the old one doesn't accelerate as good as the new one, but the idle is good with both.

We cleaned the ICV, Throttle body, new gaskets, new hoses, everything is either new or cleaned and checked. No air leaks, no fuel pressure problems, no vacuum problems. No codes with old MAF, with new MAF there is no time to scan it, since car doesn’t idle.
The mechanic guy working with me doesn’t understand what is going on. We checked every single input and output signal from and to the MAFs, there is only one signal that is a little bit different, around 0.3 Volts. This means that both MAFs are sensing the same thing, but something is wrong in the ECU. We are convinced that there are no leaks or intakes problems. This is something electronic.
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  #14  
Old 07-27-2013, 09:26 AM
ahull's Avatar
ahull ahull is offline
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Try another ICV?
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2003 330i TiAg Sport Pkg ~90k miles
DIY MODS: AA Stage I supercharger, Meyle HD FCAs w Powerflex CABs, Bilstein shocks, Meyle HD Rtabs, Angel Eyes, Clear Corners/Markers w/ LEDs, LED tails, ZHP rims, Akebono pads, AUX input
DIY E46 Merit Badges: Sunroof resurrection, CCV, OFHG, VCG w/ VANOS seals, DISA, Cooling Refresh I, steering giubo, window regs, Magnetic Infandibulator (see wiki)
DIY On deck: Rear Diff bushing. UUC SSK, clutch job eventually, Wavetrac LSD
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  #15  
Old 08-03-2013, 11:44 AM
latitude39 latitude39 is offline
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Mein Auto: E46-325xi; F34-328GT
Mileage? How many miles or km on this 318i?

O2 sensors: Replacing them made a difference on my wife's E60 3.0 liter (N52), especially the pre-cat pair. The idle would wander around +/- 50-100 RPM. Now it's stable and you can't feel the car idling. My E46-M54B25, which also got 4 new O2 sensors at 120k miles, idles better now.

You mentioned in post #8 that you changed [the] O2 sensor. The M43 has 2.

I'm just probing around. It sounds like you've done your homework on this one. But just maybe you haven't changed both O2 sensors.

I'd like to hear you success story when you get things fixed.

Good luck.
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Last edited by latitude39; 08-03-2013 at 11:49 AM.
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  #16  
Old 08-23-2013, 11:24 AM
Hotman-525 Hotman-525 is offline
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Run at least 200-250km with the new MAF first, then check again. Is there any rpm play while idling (before stall)
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  #17  
Old 08-23-2013, 12:49 PM
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SJBimmer SJBimmer is offline
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I think smolck mentioned a problem like this a while back. Not certain, but I believe a new throttle body solved it. This was on a 6 cylinder car though, and my memory is a bit scetchy as this was a long time ago. You may want to post this on a British BMW forum They have the same model as you over there.
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