3.0si - Unplugging the MAF?

[seismic22]

Hi there,

Long story short, I bought my coupe after it had stood for approximately 7 months. Car is cracking but low down power output sometimes seemed a bit lacking and I seemed to be struggling to get the same MPG other people have reported. The idle when cold was also slightly up and down but did get better when warmer and the car seemed to have minor flat spots when cold for first couple of minutes too. Plugs are not new but appear ok condition wise so after changing the air filter I decided to unplug the maf, results:

Good
Alot more torque
Much better throttle reponse when "sport" is turned off
Slightly better MPG
Smooth idle

Bad[/b]
When cold revs seemed to increase for first minute when starting as and when the brake pedal was pressed.

I have since driven the car with the maf un plugged and plugged in across many miles in different road conditions and I am convinced there is no placebo effect here and unplugging the maf noticeable improves / resolves the issues described above.

Car is showing NO CODES on INPA. When I first scanned the car there was an intake Vanos code but this hasnt come back once since I have had the car.

So I guess its either going to be a vacuum issue or maf issue. I havent taken anything apart but I cant seem to see any vacuum leaks and have sprayed the intake area hoses with brake cleaner and not noted the revs increasing. The only two other things worth mentioning are as follows:

• I can hear a minor hissing from the drivers side but cant seem to locate this and not from research other people have mentioned this as occurring with their cars
  
  When removing the engine oil cap with the engine running a drumming sound can be heard clearly. This can be heard with the oil cap on but very very faintly.

What are peoples thoughts on the cause of the problems and what the next steps are to resolve it?

Any advice welcomed! Thanks.

 

[Mike6]

Might be wrong but I think others have said you can clean the MAF

 

[GuidoK]

First measure the maf with a scope to see if the maf is fine.

Dont clean the maf as it can destroy it. A maf shouldnt be cleaned. Its an expensive, delicate part. Always first diagnose a problem before you try any fixes. Doing it the other way around never ends well. Like a doctor blindly feeding you medication.

 

[seismic22]

Whats a scope and how do you measure the maf with it? I have seen various methods on the web but not sure how I can get live data.

Thanks

 

[Marius]

Sounds like your maf sensors is knackered (faults only comes when they 100% dead) ,get new genuine one and car will run even better ,don't bother with cheaper alternatives from euros or ebay.

 

[jabber]

Have you checked the rubber boot that attaches to the throttle body, had issues with my z4 and found a split in it only noticed it when I was removing my knackered disa valve

 

[jamie_z4]

the eccentric shaft sensor sounds a lot like all of the issues you are having, i had the same on my E92. unplug that (its under the plastic engine cover at the front in between cylinders 1 & 2 in the middle of the rocker cover & report your findings.

 

[Smartbear]

Have you checked the rubber boot that attaches to the throttle body, had issues with my z4 and found a split in it only noticed it when I was removing my knackered disa valve

The op has a coupe with the n52 engine, they don't have the separate spur branching off the rubber boot which the m54 engine has
It can obviously still split, but loses the common problem part :?
Rob

 

[Chris_D]

First measure the maf with a scope to see if the maf is fine.

Dont clean the maf as it can destroy it. A maf shouldnt be cleaned. Its an expensive, delicate part. Always first diagnose a problem before you try any fixes. Doing it the other way around never ends well. Like a doctor blindly feeding you medication.

I dunno Guido. I'd suggest that when you're at the point of replacing the MAF in order to fix an issue that as a last resort, giving the MAF a few blasts of carb cleaner to see if it resolves any issues can't hurt. Much cheaper potential solution than buying an expensive new MAF.
I did this as part of a rough idle issue. I cleaned the MAF and the rough idle went away. Go figure....
EDIT: I should also add that I cleaned the ICV at the same time so ultimately it could have been either the MAF cleaning or the ICV cleaning that addressed the issue. However, cleaning the MAF did not do any harm.

 

[GuidoK]

I dunno Guido. I'd suggest that when you're at the point of replacing the MAF in order to fix an issue that as a last resort, giving the MAF a few blasts of carb cleaner to see if it resolves any issues can't hurt. Much cheaper potential solution than buying an expensive new MAF.
I did this as part of a rough idle issue. I cleaned the MAF and the rough idle went away. Go figure....
EDIT: I should also add that I cleaned the ICV at the same time so ultimately it could have been either the MAF cleaning or the ICV cleaning that addressed the issue. However, cleaning the MAF did not do any harm.

As a last resort it will be cheaper to let a competent indy that knows how a maf and oscilloscope works diagnose the maf than putting down £250,- for a new high quality MAF you just destroyed due to unnecessary cleaning plus figuring out what the rest was wrong.
If your maf needs cleaning, you have a filter problem (or air leak from somewere). Otherwise a maf usually dies from corrosion on the hot filament, and that is something a maf cleaner also cant remove.
Obviously if your maf is dirty for whatever reason you can clean it, but if its not, its best not to clean it. Not all maf's react the same to cleaning. Its an expensive part to mess around with. Only clean it when the problem is diagnosed to the MAF.

Whats a scope and how do you measure the maf with it? I have seen various methods on the web but not sure how I can get live data.
Thanks

Scope=oscilloscope. Basically its a very fancy voltmeter that graphs volt versus time. Most maf's are pulse controlled, so 'digital' and if you capture that data and analyze it, you can see if the maf is working or not, as you can exactly see the maf voltage, not an interpretation by the ecu. Look on the youtube channels of scannerdanner or south main auto for interesting diagnose video's. They also have video's on how to diagnose dirty maf sensors.
But you have inpa, why not read out the live data from what the ecu thinks the maf is measuring, and see what kind of liter/per second (or kg/hour is I believe what inpa shows). See if you see difference between maf connected or disconnected. See if it gets into closed loop at all with the maf connected. And look at fuel trims.

Most problems on most forums start with what you all can do to fix 'a problem'. clean this, replace that, etc etc.
First answer should be: what do you measure/diagnose; especially if its engine related, because how the engine runs depends on how the ecu thinks the engine runs. Thats my advice/view anyway.
Its strange that your ecu doesnt throw a code with unplugged MAF (it might take a few minutes). Somehow I think that would be impossible.