rough idle

[Uncle Al]

I have a Z3 1.9 M44 with a rough idle
I can read live data with a scanner and would like to know what the reading should be for the MAF sensor
Anyone know

[Brian H]

Hi Al,

Welcome, although I do not have the info you have requested re the MAF, if you think there is a problem with it just disconnect it and the cars ECU will revert to a factory setting. There are also a couple of known issues which affect your type of car/engine: -

• Cam shaft sensor
  Split air intake hoses

The M44 at idle can be slightly lumpy (some have even been described it as agricultural).

HTH

Brian

[Uncle Al]

Hello Brian and thanks for your reply.
Carefully checked all the intake pipes and found nothing wrong.
Pretty sure the MAF sensor is faulty as it only reads 0.37 and does not alter with increase in engine revs.
Any thoughts on the cheapest place to buy one

[colb]

If the MAF is showing no response to throttle openings then it's probably toast, you could try cleaning it with electronic spray cleaner to see if that makes it respond. If that shows no change then it is surely toast and replacement will be required.
From my experience buying aftermarket MAF's is a waste of cash, been there and done it, expensive but best bet is OEM from BMW.
Replaced mine eventually with OEM and cleared the bad idling I had straight away.
When you have a working MAF and monitor it with your meter you will see the readings increase with throttle openings and drop with throttle closing.

Colb

[bowei001]

I agree about using an OEM MAF, the pattern ones are not very reliable (at least, the one I bought wasn't so I had to replace it within about 6 months). You might like to try Worldcarparts in Lincolnshire (01526348504 and they have a website) for prices. They sell genuine Siemens and VDO MAFs and when I bought my MAF from them (along with 4 Bosch lambda sensors) they were a lot cheaper than going to BMW and the parts were identical to those BMW would have sold me.

[Brian H]

BMMINI parts supply OEM parts at a discounted price, they can be found at http://www.bmminiparts.com.

[pingu]

You can also search the net for salvage parts. I'd rather buy a salvaged OEM part than a Chinese replica.

[Uncle Al]

Thanks for all your help.
I have ordered a second hand Bosch unit.
For £25 I guess it's worth a try.
I'll post the outcome in due course

[Uncle Al]

Second hand MAF fitted and working well..
Still chasing rough idle and constantly appearing Multiple Random Misfire codes
Checked the fuel pressure and now know what it is. Only problem is that I don't know what it should be !
Anyone know the info I need.
It's an M44 engine.
The readings are 2.6 Bar at idle and it drops to 2.4 Bar when held at a constant 2000rpm. If I disconnect the vacuum pipe to the fuel pressure regulator the reading is a constant 3.1 Bar

[Del]

When does it idle roughly? On the first cold start of the day, when warmed up or all the time?

[Robert T]

Are there any other codes than misfire showing? If not, then we recently sorted an M44-engined 1.9 with a misfire on one cylinder when warm by replacing the coil pack. Check plugs and leads as well by swapping them between cylinders - if the problem doesn't move, then it might be the coil pack. We tried my coil pack on his car and that seemed to cure the misfire, so he bought a used one for minimal cost and car seems to be running okay now. It could also be a camshaft sensor - they don't always log error codes - I guess if the values aren't far enough out of range, then the ECU won't record it as a fault. Also, the M44 is known for having a slightly lumpy idle and BMW have a piece of advice to retard the timing slightly to improve it - I have had this done to mine.

Cheers R.

[Uncle Al]

Thanks for your replies.

The idle is rough when it is warm. It starts and runs normally from cold.

The codes are always random multiple misfires and also specific cylinders but never the same cylinder each time.

I have changed the plugs and the HT leads. I have also carefully checked for a vacuum leak.

The compressions are good too.

Car feels as though it's running too lean with an almost noticeable flat spot when moving off. Also sounds a bit fluffy at the exhaust tailpipe.

[Del]

The Haynes manual (US version) says "fuel pressure regulator rating" 43.5 + or - 1 psi. Which translates to 2.93 to 3.06 bar.

[Uncle Al]

Yes the fuel pressure regulator has 3 Bar stamped on it so I'm guessing that the system should run at 3 Bar, but not above

Interesting about the camshaft position sensor though. The car has done a genuine 60000 miles and has never shown a code for the CPS but keep hearing about them being changed.

[Pierrick]

Hello Brian and thanks for your reply.
Carefully checked all the intake pipes and found nothing wrong.
Pretty sure the MAF sensor is faulty as it only reads 0.37 and does not alter with increase in engine revs.
Any thoughts on the cheapest place to buy one

Hi uncle, where and how do you mesure this??

Thanks.

[Del]

My forum guess is a possible DISA valve issue (random, generic misfire codes). I would expect the camshaft position sensor to show as a specific fault code. These are plastic units bolted to the inlet manifold. They change the passage of air at certain revs to optimise torque. The unit comprises of an electrical “switch” wired to the ECU and a mechanical “butterfly” flap which deviates the airflow. The faults that can develop are:-

1) The flap can become loose on its sprung spindle and either become noisy or become disconnected from the spring so that it dangles loosely. Mine was already very noisy when I bought the car at 68,000 miles and I changed it at around 70,000 miles.

2) There is an orange rubber seal that can break down, perish and cause a permanent vacuum leak or

3) Something can go wrong with the electrics in the “switch” – but this would normally show up as an error code.

I would stress that I am only offering an educated guess (as a fellow M44 owner). I did spend many months chasing a cold start misfire. You may want investigate further and plug the car into a specific BMW diagnostic code reader before parting with around £150 for a new one.

[Pierrick]

Thanks del! This might help me as well as I have exactly the same problem! I wanted to investigate the disa valve but didn't know where it was! I thought it was on the exaust side...

So, it cost 150£ new? and it seems easy to acces! Can I remove it to have a look at it and put it back? or i'll need to change a seal or something?

[BladeRunner919]

Thanks del! This might help me as well as I have exactly the same problem! I wanted to investigate the disa valve but didn't know where it was! I thought it was on the exaust side...

So, it cost 150£ new? and it seems easy to acces! Can I remove it to have a look at it and put it back? or i'll need to change a seal or something?

Yes, you can just remove them - I've had mine out. There's not really much to see, though. Mine's really noisy, which is why I took it out but I didn't really learn much from doing so.

[Pierrick]

Ok, and when you take it out, what is it possible to do to clean?? or change a small part?? or make some mesures to make sure it's working properly?? I have no idea what it looks like!

[BladeRunner919]

Ok, and when you take it out, what is it possible to do to clean?? or change a small part?? or make some mesures to make sure it's working properly?? I have no idea what it looks like!

There doesn't seem to be that much you can do once it's out, other than make sure it's not broken. It takes about 5 mins, so why not whip it out and have a look.

[Del]

Ok, and when you take it out, what is it possible to do to clean?? or change a small part?? or make some mesures to make sure it's working properly?? I have no idea what it looks like!

Fair question Pierrick, the attached article (whilst referring to a different model DISA) gives a more rounded picture of the possible problems. They do “play-up” either electronically or mechanically – as shown, the symptoms are a lean mixture. The diagnostics on the M44 engine are not that sophisticated in terms of pinpointing problems with error codes – even on BMW software – a fact acknowledged to me by an ex-BMW master tech. My understanding is that when they (DISA valves) start to get noisy they are on the decline. I changed mine at this point as I was scared by BMW forums I had read about the valve/flap falling off into the inlet manifold and damaging the engine.

Mine was making a very loud buzzing and “clackity” noise. Even before I got to know the car I wondered what on earth the noise was as it was so pronounced. The new one was silent.

When faulty they seem to cause lean mixture type issues. The originator of this thread has checked most things already and used another MAF. He has also checked fuel pressure and I know that even though a coil issue would only show as a “general misfire” on the M44, it would show up on the cylinder in question and not as the random misfire feedback being given in this case.

You can never be sure on just a forum, but I thought this was sufficient to at least put the DISA down as a possible suspect in this case.

When in good working order they seem to be quiet, the flap (similar to the valve in the throttle) is properly sprung and the gasket is not leaking. I am afraid that I don't know how to test one electronically.

http://www.bimmerfest.com/forums/showth ... ?p=5821235

[colb]

OEM Diagram of Inlet manifold & Disa here
http://www.realoem.com/bmw/showparts.do ... g=11&fg=40

Mine started clacking, replaced it for silent operation.

Colb

[Pierrick]

OK! Thanks guys! i'll take it off when I have a bit of time and have a look at it! If it looks liks something is wrong or if there is some play in the mechanical parts, I may change it! Depending on how much a new one would cost me!

What kind of moise does it make?? Anyone has a video?

[Pierrick]

OK! Thanks guys! i'll take it off when I have a bit of time and have a look at it! If it looks liks something is wrong or if there is some play in the mechanical parts, I may change it! Depending on how much a new one would cost me!

What kind of moise does it make?? Anyone has a video?

[BladeRunner919]

I suppose an honest answer is that if you don't know what it sounds like, yours is probably ok!!

When I'm listening for sounds in the engine bay I use a length of tubing as a kind of stethoscope - put one end to your ear and use the other end to probe around. That way you can listen to specific components without having the sound drowned out by engine noise (or having to put your head into the engine bay of a running car!).

[Del]

As bladerunner919 suggests, the noise is loud and obvious from the black plastic cover. Most of the YouTube videos are from the US and appear to relate to the slightly different units put in earlier 6-cylinder engines. The unit is a bit of a "Bavarian secret" and I certainly don't know the precise internal workings of the unit . The following text is what I collected online at the time:-

DIfferenzierte SAuganlage ("Differential Air Intake") valve (aka DISA valve)

"The DISA valve has an outer seal (inside the manifold) and a diaphragm inside the valve itself. The valve is constantly fed 12 volts during normal throttle operation and then open circuits on higher RPM and throttle opening. This de-energises the coil which stops the manifold vacuum from reaching the diaphragm. The butterfly then springs open."

“Optimizes the engine’s running under partial and full load as it adjusts the intake manifold runner length to improve engine performance. The DISA valve is located in the inlet plenum chamber and controls the variable length intake manifold giving better torque at low revs by closing, keeping the intake runner long. After higher engine speeds, it opens up and makes the intake runners shorter for more horsepower. When it fails it can lead to a rough idle, reduced performance and at times a rattling noise or Check Engine light. Suspect the DISA when the engine has over 60-80K miles, shows signs of rough running (random misfiring), codes P0171 and P0174 or reduced performance.”

“The BMW DISA valve, otherwise known as the "Intake Manifold Adjuster Unit" is located on the side of the intake manifold and opens and closes depending on engine RPM and throttle position. Due to the materials used in the original design, the valve internals can wear out prematurely. If a worn out DISA valve is not replaced or repaired, pieces of the valve can eventually break apart, travel through the intake manifold and into the engine, where they can cause severe engine damage. Symptoms included rough idle, lean engine codes, reduced engine performance and a rattling noise from the intake manifold area. Don't take a chance, check out our long term solution to this common problem.”

[Pierrick]

I just checked mine... it needs to be changed! I looked carefully and the "rubber valve" (con't know how to call it) which open and close the butterfly via a steel rod has cracked! And it makes a noise... mot a big one but you can clearly hear it when the bonnet is open!

I'll post photos later!

So now... where to buy one?? New one will be expensive I guess! I'll probably go for a second hand one!

[Pierrick]

Only for those interested... here is the noise a DISA valve makes when going bad!

http://www.youtube.com/watch?v=6YEbogSv0Hk

[Del]

That one is certainly making a loud "clatter" when the engine is revved. Mine was generally very noisy even at tick-over. They are quite flimsy, plastic units and the odd bit of internet information I could find suggested that if buying a second-hand unit, there was a significant risk it would be almost as bad - because they tend to come from the older 4 cylinder engines. This is what made me go for a new BMW unit in the end.

[Pierrick]

The one on the video is mine!! It makes noise when coming back to idle, then is quiet!

Anyway, I found a new one from BMWmini parts for 75£... i think it's a good price! how much did you pay for yours?

[Del]

Anyway, I found a new one from BMWmini parts for 75£... i think it's a good price! how much did you pay for yours?

From memory about £145 at the end of 2011 - that £75 is a marvellous price I wouldn't hesitate in reaching for my credit card for that price - a bargain