# Update on the suspected bad MAF



## RKT BMR (Sep 7, 2002)

Well, the new MAF arrived today (gotta hand it to Pacific BMW...). I also finally got around to buying an OBDII code reader at lunch today, thanks to the prodding of Mr.Paddle.Shift, and read out the codes that were lighting my Service Engine Soon indicator.

(Those of you who are familiar with my modification exploits might wonder how I went this long without a scan tool, and you'd be on solid ground with your incredulity; I can't explain myself, so I won't try  )

Here's what's going on:

P0171, 174: Running lean, banks 1 and 2

P0313: Misfire (I know what caused this, so it can be ignored)

P0369: Camshaft position sensor "B" circuit intermittent (this one has me a little concerned, and it showed up again right after I cleared the diag codes out, so needs more investigation; hope it doesn't have anything to do with the engine cleaning I did before the 'fest  )

P1191, 1193: Pre and post cat fuel trim problem

So, the codes that are really meaningful here, 171,174,1191, and 1193, are all consistent with a contaminated MAF. If some oil has gotten on the thin-film/wire in the MAF, it would cause the sensor to indicate less airflow than is actually occurring, resulting in a lean mixture.

I cleared the codes (and the MIL/SES light), and plan to run with my existing MAF until I get an MIL again, then check the codes. If the same, I'll clear it again and go one more round to see what turns up. If I get the same basic faults, I'll swap the MAF, clear the codes, and then see what happens.

I'm betting the MAF's the problem, but I can't know for sure until I disassemble it, which from what I can tell will be a destructive project.

If not, my next step is to invest $122 in some OBDII scanning software for my laptop so I can monitor and record engine operating parameters in real time while driving, and catch the failure. Then I can get a better idea of what's going on. I plan to purchase a copy of Vehicle Explorer, which looks like a pretty decent tool. For the technically minded, you should click the embedded link and check it out.


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## doeboy (Sep 20, 2002)

Buy a GT One!  Yeah right.... I wish I could afford one of those...   :rofl:


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## RKT BMR (Sep 7, 2002)

doeboy said:


> Buy a GT One!  Yeah right.... I wish I could afford one of those...   :rofl:




Sorry, buddy... that was the only response that seemed appropriate 

As you're probably aware, I was itching to get an Actia PassthruXS+, and was soliciting a joint buy of some sort, but have abandoned that project since apparently BMW is determined to preserve the cash cow of car/key memory setting theft revenue for their "independent" dealers.

Man, that one pissed me off bigtime.


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## Kaz (Dec 21, 2001)

Hmm, I think 0369 is what I had when my exhaust camshaft sensor went out (not an uncommon problem). The car will occasionally idle funny (too high in my case, IIRC) and the MIL will go on and off.


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## Mr Paddle.Shift (Dec 19, 2001)

Dave,

Maybe changing the MAF might work better. Question I have is did the lean code come on during light throttle or heavy throttle, highway or street driving?

As for 0369, it sounds like the sensor is faulty. "Intermittent" is definitely not good.

And what's the reason for 0313?

EDIT: Actually, I was hoping at least a 0100, 0101 or 0102. None of these appeared?


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## RKT BMR (Sep 7, 2002)

*Update*

First of all, thanks to Mr.Paddle.Shift -- he's a candidate for bonafide savior at this point. 24 hours with a scan tool and the picture is very different.

I've had the chance now to reset and relight the MIL twice since yesterday. The results are very interesting, and completely different than the path I was going down.

So here it is. The problem seems to be the cam sensor. After resetting yesterday, I had another P0369 immediately after starting the motor, without an MIL (must be one of those conditions that has to show twice before it lights the MIL). Cleared that (remember, no MIL), and then started up and went on with my day normally.

After two starts and a drive home, the MIL lit again. Pulled the code: P0369, and no others. Reset yesterday evening, and went on with my life.

This morning, again over the course of two separate starts (leave for work, get gas) and 30 miles of driving, MIL lights again. Pulled the codes. Again, P0369 and nothing else.

A pattern is emerging here, don't ya think? Cleared it again after I got to work, and will run this pattern/cycle again a few more times just to build up a set of data to take to BMW.

Kaz, sounds like I have a bad camshaft sensor. I do notice some performance issues: Idles fast now and then, but I can't discern a particular pattern. My normal idle is around 650, and totally smooth. When it is idling fast, it's around 800, more or less. This is when the engine has been running and warmed up, and I can't make it happen, or go away. Just happens seemingly without cause.

Also, I've noticed a very real power loss at times when the MIL is lit. Not as soon as it lights, but seemingly randomly -- seems to be correlated with start cycles. I.e., get in the car, start it, runs like a rocket. Come back later, get in the car, start it, runs like a slug, even though the motor is very smooth.

When I clear the DTC codes, the car is always peppy afterward.

I can theorize all sorts of scenarios that a bad cam sensor could cause the ECU to be hunting fuel trim and adaptation values to get the O2 readings to come in line, and be doing all the wrong things because of bad data coming in from the cam sensor. Then, when the algorithms fail to find a good fuel trim value/pattern, the ECU falls back on the default "limp home" values, hence the crappy performance.

Through all this I can see how those other DTC codes could result from out-of-spec operation of the motor. Finally, I suspect that what the BMW tech pulled from the ECU was the generally the same set of codes I pulled -- lean mixture, fuel trim problems, etc. This would lead to a possible MAF problem, assuming the other sensors are working right.

The scan tool has been worth its price in just a single 24-hour period, as it has allowed me to do some diagnosis that just wouldn't be possible otherwise... I'll bet if I let things go with the MIL lit long enough, those other errors and codes will eventually show up.

Thoughts?


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## RKT BMR (Sep 7, 2002)

Mr Paddle.Shift said:


> And what's the reason for 0313?


With a bad cam sensor, I can think of reasonable ways that misfires and mixture problems could occur, explaining 313, 171/174, and 1191/1193.


Mr Paddle.Shift said:


> EDIT: Actually, I was hoping at least a 0100, 0101 or 0102. None of these appeared?


Nope!

_EDIT: 131 should have been 313... corrected_


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## Kaz (Dec 21, 2001)

When my cam sensor was bad, it's biggest (yet not always there) symptom was the slightly high, sometimes hunting idle. I didn't really notice any drivability issues, though on occasion it would feel like it was missing at idle. Since this seems to be a common problem on early M54s (and I believe it's not that expensive a part or hard to replace) you may want to start there.


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## Mr Paddle.Shift (Dec 19, 2001)

Dave, 

Good update. Definitely get the sensor changed. I had a similar incident too when I forgot to disconnect the cam shaft sensor after some *work* done in my car. Exactly like what Kaz and you described, erratic idle, etc.

Another thing about a bad MAF is that it will definitely have to spit out a 100,101 o 102 code.

Keep us posted!


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## RKT BMR (Sep 7, 2002)

Mr Paddle.Shift said:


> Dave,
> 
> Good update. Definitely get the sensor changed. I had a similar incident too when I forgot to disconnect the cam shaft sensor after some *work* done in my car. Exactly like what Kaz and you described, erratic idle, etc.
> 
> Another thing about a bad MAF is that it will definitely have to spit out a 100,101 o 102 code.


Thanks.

No doubt about it now... It's the cam sensor. I've been through at least 5 cycles now of clearing the diag codes, and having the MIL light again after some driving (just as it did before I got the code reader), and every single time it's been just the 369 code.

I'm going to assume at this point that the other codes that were in there were related to the cam sensor being bad. After all, I'd driven for months since the ECU was cleared by BMW when I took it in (and they suggested a bad MAF), including a trip to the fest and back, with all the hard driving involved, etc.

So, the MAF goes back to pacific, and I order a sensor. I'm gonna check the integrity of the wiring harness and the connector first, though, to make sure it's not a bad wire or connector -- although that's very unlikely.

Then, we'll see what happens. Nice thing about having a reader now is that I can check now and then to see if there are any pending codes (that wouldn't light the MIL) after correcting the sensor issue, which might hint at other problems related to those lean and misfire conditions that showed in the first dump.

I'm pretty sure those were anomalous at this point, however, as I'm not getting anything other than the 369 now.

What's your preferred brew? :drink:


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## Mr Paddle.Shift (Dec 19, 2001)

Dave dude, no worries about the brew. Just show up at the TS. :thumbup:


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## NetSeven (Sep 24, 2005)

Im having the same exact codes and problems on my 2001 330I so im going to go ahead and try to replace the cam sensor. I looked it up and there are 2 listed, intake and exhaust. Which one is the one I need?


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## NetSeven (Sep 24, 2005)

http://www2.bimmerpartswholesale.co...gory=A&part=Camshaft+Position+Sensor&dp=false

Here is the site im looking to order it from once I find out which one I need. Also where exactly on the engine is the camshaft sensor located? I know its on the head but where exactly so I dont have to look around for it.

Thanks


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## THacker (Apr 21, 2005)

I had the same DTC P0369 on a 525i.

I replaced the exhaust CPS (the one without the tail). It ran well for two months then trouble light again. This time a Peake tool said it was the intake CPS.

Probably best to replace both when you get the P0369 code.

Note that the intake CPS is buried and pretty difficult to replace on the 525 - whereas the exhaust CPS is a 10 minute job.


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## edsmax (Jul 28, 2003)

NetSeven said:


> http://www2.bimmerpartswholesale.co...gory=A&part=Camshaft+Position+Sensor&dp=false
> 
> Here is the site im looking to order it from once I find out which one I need. Also where exactly on the engine is the camshaft sensor located? I know its on the head but where exactly so I dont have to look around for it.
> 
> Thanks


From my research in searching this site, 0369 USUALLY means its the exhaust cam sensor. 0344 is the intake (the code my car was creating).

Exhaust cam sensor is easy, intake is also easy but involves removing the VANOS solenoid. Do a search or better yet, buy a Bently manual.

Ed


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## Paul "B" UK (Apr 7, 2008)

*Uneven idling too!!!!*

Hello there Greetings from the UK - It Sounds like I have a similar problem with my 2001 -525 also, starts fine but then when it's warmed up runs erratically and "lumpy" I have been advised it could be an air leak on the inlet as the mixture is lean - but not sure how to find it?? dont have access to a smoke analyser - any advice guys??


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## bmwrules123 (Aug 15, 2010)

Hi guys,
i am new to this forum just bought a 320 d se y plate couple of weeks back and it started giving me all sorts of problem. i would really appreaciate if you experts can throw some light into it. i have recently started getting htis loss of power/intermittent acceleration recently. when i am moving off in 2nd gear in a higher rev it give s a creeky noise at 3000-4000 rpmwith lots of black smoke. when i am driving lets say 0n 60 miles and trying to spped up with foot on the floor it just doesnot go any further just stays at that speed and gives me that creeky noise. if i take my foot off the gas and try 2 3 times to accelerate some times it responds well with steady acc. i have had the car diagn in a bmw dealer only thing they came up with only is the maf has been replaced with a improved one-dont know the details, so they upgraded the software assuming it will sort out the problem. the catconverter has been replaced along with the full exhaust system. so there is no fault codes. problem is still there just loss of power with no pulling power.please suggest me.


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