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2001 E46 325i, Engine running problem, new to the site, help please!

4K views 34 replies 10 participants last post by  P4 ULF 
#1 ·
Hi guys, I've just bought myself my first BMW and am over the moon with it, but, I've got a problem with the idling. When I start the engine, the revs sit at about 750rpm and then drop to about 500, and then back up again, it keeps doing this and when I press the throttle, they drop further, almost to a stall. When moving away, they continue to drop, even if I raise it to about 2000rpm and have stalled it a few times. It seems to sort itself out after a while so I wasn't too concerned but tonight, after a 15 minute drive, I parked up for about 10 mins and the EML light came on. It wouldn't rev at all so, I turned the engine off, started up again and drove home fine. The car is a 2001 325ci M Sport. I'm loving the way it drives and would be really grateful if anyone could point me in the right direction. My mechanical skills are basic to say the least so please, bear with me! Many thanks in advance :)
 
#2 ·
I would be checking for any air leaks from split hoses, split vacuum pipes, split engine breather pipes or split induction pipes, also any valves and diaphragms that may have failed. Any air that is sucked into the engine should travel past the Air flow meter otherwise it will give you a running fault and can trigger a Airflow meter fault code.
 
#3 ·
Thanks for the response, I did have a quick look earlier and couldn't see anything obvious, but to be honest, I'm not even sure which pipes I should be looking at!! I haven't had a car with an engine bay as packed as this before so it's a bit tricky!
 
#4 ·
Check the pipes going from the airbox to the throttle.

It does sound sensor related tbh try cleaning the AFM see if that helps
 
#7 ·
Get the codes cleared and drive it for a few miles then have them read again and see what comes up. You need the codes to point you in the right direction really.

It does sound a little like an air leak but the problem wouldn't go away if it was. Get the car in 2nd gear at about 1500rpm and accelerate full throttle to about 4000rpm. If you have an air leak you will know about it. The engine sucking air in that hard will amplify any leak you have and show some signs, most likely the car will 'kangaroo' really badly. Also you said the engine wouldn't rev and turning it off and back on fixed it, to me this sounds electrical, maybe a sensor on it's way out.

It's a shame you're so far away or I would pull the codes and have a look around it for you. If you're ever up in the NW of England give me a shout!

Scott.
 
#8 ·
Thanks so much for the response guys :thumbsup I've found a BMW specialist near me so will arrange a fault code test during the week hopefully. Is it worth me disconnecting the air flow meter to see if it helps? Any idea how much a new one would cost? And Scott, that's very kind of you but, with the fuel this thing drinks, I'd have to empty my savings to get there! I have had the kangaroo-ing effect, so will try the 2nd gear test, as soon as I've forgiven her for upsetting me last night!
 
#9 ·
Yeah I have a 325Ci and that drinks enough! I feel your pain....

As for the 'kagarooing', if it does it under hard acceleration in any gear really I would certainly be looking for a leak on the intake. I had one on my 318i, as the engine shifts it's weight and lurches back under hard acceleration it can extend the intake tubing slightly causing any cracks to open up a fraction more or loosen a bad joint a bit more. This coupled with the engine sucking harder meant it let a lot of un-metered air in. This totally throws the ECU into a wobbler. The MAF is saying there is not enough air, the lambda sensors are saying there is too much so it just kind of cuts out and starts again (this takes a fraction of a second). This gives you the kangaroo effect!

Don't let them scam you on the code read. I wouldn't pay more than £30 at the most...

Let us know.

Scott.
 
#10 ·
if you are brave enough,you could buy a daignostic fault code reader from ebay and read the code yourself.
the code readers from ebay for e.g the Autel MS309 is what i bought for about 40 quid and did the job for me.This does not give you bmw specific codes but gives generic fault codes.It can also be used on most obd2 complaint cars.
it paid for itself after i used it once and it continues to save cash each i need to use it.
that is my experience so far.
 
#11 ·
If you get one of these I have some free software that will read and erase codes for you. There is also some software that will give you live data from all the sensors in the engine while it's running. Pretty handy and quite interesting tool. All you need is a laptop or netbook with a USB port that you can take to the car.
 
#12 ·
Thanks again guys, I think I'll ring the garage first and see what the damage for a fault code test will be, and then decide whether it's worth buying one of my own, after all, I'm hoping I won't need it too often!! Started it up this evening and the revs were still fluctuating between 500-1000rpm by themselves, pulled away, put it in second and accelerated from 1500-4000rpm and is was perfectly smooth, revved and pulled cleanly. So, I'm guessing this would mean an air leak is less likely and possibly down to a sensor or airflow meter instead?
 
#13 ·
Just phoned the garage and was quoted £50+vat for engine diagnostics or £65+vat for full body diagnostics!! Having seen the price of the one you suggested Scott, it seems a bit of a no-brainer! Shame though, I was hoping the garage would've had reasonable rates as I've got some other issues with rear suspension height (which i'm guessing is down to the previous owner replacing the springs with non genuine ones), grinding under de-celleration and heater fans with a mind of their own!! Has it put me off my new motor...hell no! :D
 
#14 ·
Ok, I found someone with diagnostic equipment and took the car round to him this evening. The reader he had was called an Easy OBD2, and there was 2 faults that came up to begin with, one being the cam sensor and one, the 02 sensor. He ran some tests and it looks like one of the 02 sensors was getting less voltage to it than the other(s), not sure how many there are? It seemed to be giving readings for 4! Apparently, this meant that it was running rich. I asked for the codes but, by the time he'd finished doing everything, the second one had dropped off and was only showing P0014 (cam sensor) as pending. I think the other one was P0161, but not sure. Any ideas how much an 02 sensor would be? Thanks in advance.
 
#16 ·
Having done a bit of searching, it seems my idling problem is somewhat common!! I've heard everything from cam sensors, 02 sensors and idle control valves, to replacing vanos seals! I think my plan of action will be to clean the idle control valve, then look at 02 sensor and cam sensor and if need be, vanos seals (as this seems to divide opinion). However, I tried disconnecting the airflow meter with it running today, and the engine cut out immediately! Wasn't expecting that! Would this point to a faulty airflow meter?
 
#23 ·
Cleaned the idle control valve yesterday and still no improvement. So, next step is cam sensor. Am I right in thinking it's the inlet one I want? I'm gonna go for a genuine one having read some of the comments regarding aftermarket ones! Is it just a case of plug it in and go with these? Tried looking on realOEM to see where it goes but the diagram didn't really help :s
 
#27 ·
Yeah checked the pipes and couldn't see any cracks at all! I thought the small piece that goes from the lower intake pipe to the idle control valve had a loose hose clamp and wasn't joined properly, but having put it back on, there's still no sign of improvement, so I guess it wasn't that! Probably going to get the cam sensor tomorrow, just concerned about spending £80 if that isn't the problem!!
 
#28 ·
I got the exhaust and inlet cam sensors from bmw yesterday. Fitted the exhaust one, started the car this morning and no improvement. Had a look to see if I could do the inlet one, (which I can't as I don't have the tools to remove the oil filter housing cap or vanos intake solenoid) and noticed that the black pipe, next to the solenoid (heard it called a pcv pipe?!), was broken, put some electrical tape round it for now. My question is, what does this pipe do, and could it be giving me these problems?
 
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