Running issues

[martauto]

Hello, e46 325 cab auto se 2004 92k.

Not long after I bought the car she started to run poor so after loads of coil packs, new plugs and a few air leaks sorted we went on to buy top range petrol but she still runs irractically but only when hot.Going to work this morning (20 min trip) she was perfect, on the way home after 15 mins she started to what seems like miss fireing but when pushed she was like the devil, awesome.

We had a light on saying no2 sensor was faulty but they were cleared last week and nothing has come back. I am doing 26 mpg around town and 37 on a mixed run which I thought was OK.

A little bit stuck here so any help please ?

Posted on the e46 zone as well so your not seeing double. lol.



Mart.

[martauto]

OK So I bought four prong bosh plugs at £13 each and the car ran so badly it was an absolute nightmare to control.
They came out and the others went back in (they had all burnt nicely had the previous set) and I disconnected the engine positive lead for one hour and started her up and left her for half an hour.The next day she ran great but coming home there was what I would say was over fueling, if I just tickled the gas pedal she ran fine but asked it a question she hesitated and only "seemed" to miss-fire but I think too much fuel was being delivered, I could smell it in the exhaust (top was down).
This only happens when she is up to full working temperature and I replaced most of the usual electrics so it must be down to the fueling side but I do not know anything about this side of things so can anyone help me please ???
By the way the codes have been no help at all.

Cheers and many thanks guy`s,

Mart.

[martauto]

Well I took some advice from the e46 zone and unplugged the maf sensor a few days ago and apart from the tick over needs to settle when coming to a stop, she has run like a dream.
I have ordered a cheap one so lets hope I have finally got to the bottom of this.

Mart.

[martauto]

Day five and going strong, it`s great to actually drive it properly now even since the day I bought it in April.

Mart.

[Foe]

Not sure if I've mentioned this before, but I love an update. Fingers crossed it works

[DanThe]

Beware of cheap mafs, most are reconditioned and use a resistor in place of the hot film, although it may 'work' there is no way it can measure the air in the same way the film does.
The intake boots are common for splitting where you can't see them which will also mess up the fuel mixture

[martauto]

Beware of cheap mafs, most are reconditioned and use a resistor in place of the hot film, although it may 'work' there is no way it can measure the air in the same way the film does.
The intake boots are common for splitting where you can't see them which will also mess up the fuel mixture

Cheers Dan it cant be any worse than the one I have on right now.
When I remove it , how do I check to see what is wrong with it please?

Mart.

[DanThe]

You can check its working with a multi meter but the obvious one is if you look inside it the hot film wires can be broken

[martauto]

You can check its working with a multi meter but the obvious one is if you look inside it the hot film wires can be broken

Had a look and a test and one wire was down so a good call here, cheers for that Dan

Mart.

[ah]

While your on the subject of afm’s can an E30 320 M20 be tested if so how it done.I know that the top is sealed.

[Cloggy Saint]

The cap is only sealed with silicone. Break the seal with a sharp knife and re-silicone it when your done.

[ah]

Yes but when Ive got the cap off how do I test it ?

[Brianmoooore]

Yes but when Ive got the cap off how do I test it ?

First of all, a MAF and a AFM are two completely different things that do similar jobs. Both can cause drivability problems when they fail, but the simple test for a MAF is just to unplug it. This will restore the car to almost normal performance - so close to normal that you may wonder what it was fitted for in the first place, and close enough for the unscrupulous to sell cheap replacements which actually have no working parts. Without a working one to try back to back, you'd never notice.
To test an AFM you connect a 6 to 12 volt battery across the ends of the potentiometer, and a voltmeter between one of the battery terminals and the wiper of the potentiometer. You then slowly physically move the 'barn door' from fully closed to fully open, while watching the voltmeter. The voltage should slowly change, with no dropouts or small changes of direction at any point.

[martauto]

Well a couple or so months ago we threw away the cheap coil packs and fitted a new ccv valve and pipes and she runs like an absolute dream and no smoking.
At last a car to drive !!!!

Mart.

[fixedwheelnut]

As Brian said with a voltmeter or if you can gain access to a scope, use this method https://www.picoauto.com/library/automo ... r-digital/

[martauto]

I have a 2.0 afm on my 2.5 and it`s not a problem but do you think it will need one from a 2.5?
The part no`s appear not to be the same .

Mart.

[martauto]

Well the guy`s at Cotswold say they are the same part no`s so I`m very happy.
It doe`s run very well but I was curious why a 2.0 and 2.5 should share this part .

Mart.

[DanThe]

If the diameter of the housing is the same then they will 99.9% most likely be the same part, the sensor is shared among many cars just mounted in a different housing

[martauto]

What does the sensor actually do as in measure volume etc ?

Mart.

[fixedwheelnut]

What does the sensor actually do as in measure volume etc ?

Mart.

As the air flows across the sensor the current drawn to maintain the temperature of the sensor in relation to air temperature changes in relation to the air volume drawn across it, the ECU uses this in conjunction with throttle position, engine speed and vacuum to calculate the volume of air being drawn in to the engine.

This explains it, https://us.autologic.com/news/hot-film- ... ow-sensors

[martauto]

Great post mate, I think I know whats going on now

Mart.