Air Flow Metre Talk

[dbanbery]

Now then,

after curing my running problem with a replacement AFM my problems seem to be cured. however, the replacement, while physically looking the same [allbeit a different make] had a different Merc part number on it. [it was an intermotor part with the equivilent BMW Merc Audi etc part numbers on it for fitment. the AFM for my car had a different number that didnt correspond to them at all. i fitted it anyway and it has made my car run better. is this common? or are they acutally the same. it seems to have cured my issues, but i'm not sure whether its causing any problems to the engine if incorrect..

 

[television]

These things set up the engine for the correct temp and air flow coming into the engine, they all work on the same principle, and cannot do any harm, the car runs badly when the sensor fails or becomes worn out as it gives the fueling the wrong or no info

 

[Xtractorfan]

Yes as malcolm has said, these are basically sensors and take readings from the air going into the engine, so basically they just feed the readings to the ecu. You may find problems where manufacturers include a code which cannot be read by other make ECUs

 

[dbanbery]

hmm.

this replacement one seems to be working a lot better than the one originally on the car, however, it seems a lot freer to rev from tickover when cold [not that i've been revving it hard from cold] and a little bit slow on the take up

i have just fully serviced it with 0w30 fuchs oil too with a full filter change etc. its a 202.018 [i'm sure malcolm already knows this haha]

sooo,

is this slightly different running characteristic when hot normal? or is is due to the fact the air flow metre may be slightly wrong? i'd give you the numbers, but i havent got them at this moment. they are both physically the same.

either way, it runs better than before so i'm not one to moan. its worse on fuel though!

 

[whitenemesis]

I wonder if the response factor of these units are all the same? i.e. is the voltage given out for a given set of measurement values universal?

 

[television]

I wonder if the response factor of these units are all the same? i.e. is the voltage given out for a given set of measurement values universal?

Well Bosch will supply a basic sensor that is common to most and you just fit it into your own housing, only £50 doing it this way, and I used to recommend that some 3 years ago, but its the age

 

[dbanbery]

could there be a different problem, that would surface only after changing the airflow metre?

 

[television]

Not really, the MAF sets up the correct fueling, there are other components like the 02 sensor that also do this, during warm up the 02 is doing nothing as the mixture is enriched to be able to run when cold, once the engine is warm, then the 02 sensor takes over. The MAF has nothing to do with any other part of the engine.

Another component is the EGR valve that returns harmfull gasses back into the intake at cruising light throttle driving

 

[dbanbery]

thats when the hesitation is more notciable. is there an EGR valve on mine? i thought it was a bit too old for that sort of sophistication.


and if it is the O2 sensor, id this a clean up job or a replace? i want it to run as good as it can, as these sort of minor issues do my head in.

 

[television]

thats when the hesitation is more notciable. is there an EGR valve on mine? i thought it was a bit too old for that sort of sophistication.


and if it is the O2 sensor, id this a clean up job or a replace? i want it to run as good as it can, as these sort of minor issues do my head in.

The 02 sensor cannot be cleaned, they do not last for ever due to the environment that they live in, but when the have failed or go out of spec they will turn the engine lamp on. And here too, if the MAF went faulty so as to enrich the mixture, then the 02 sensor would try and adjust. With the 02 sensor it has an optimum setting stored in the ECU, should it swing too far then the warning lamp comes on. Sometimes it will go out if it is a boarder line case, and we saw this on a C240 during the contaminated fuel issue.

This is where you just cant take readings from STAR at their face value, and one needs to think a little further a field
the

 

[dbanbery]

:roll:well in that case it should be ok. i have looked through the merc tech spec and i cant find a listing for an EGR valve. this device is a pet hate/love [whichever way you look at it] for Vauxhall owners as its popular fault on all of them

****** vauxhalls:roll:

 

[dbanbery]

Developments:

soo,

after using the car for a while and getting acustomed to its new characteristics, i have begun to notice something:

when slowing down and changing down the box, then, planting your foot on the accellerator [think slowing down for a roundabout off the motorway and then after the lights have changed to green carrying on round] there is a definate lack of power, then there is a pop/bang from underneath the car [sounds like something popping open] then it goes.

could it be an engine flood followed by a backfire? or could it be some sort of EGR valve? there isnt one on the exhaust as i have had it off when i did the propshaft centre bearing. is it in the manifold?

 

[television]

Once again this does point towards the MAF, when a car pops back it is usually weak mixture that causes this

 

[dbanbery]

ok,

but how does this explain my fuel consumption going up since replacing it? i dont think its running rich, as its fumes dont smell like a BMWs. [every one i've had or messed with has always run slightly rich]

 

[television]

When the mixture is too weak it causes incomplete combustion and the effect is a blow back. also if the fueling is wrong you could be using more fuel to compensate, I would un plug the MAF and try it,in some cases the idle may be poor.

 

[dbanbery]

i'll check that, just to clarify, it wont store a fault code will it?

 

[television]

i'll check that, just to clarify, it wont store a fault code will it?

I have never known one to do that, SAM says that it can, but never one reported here and I have said this several hundred times

 

[dbanbery]

LOL.

sorry, i wanted to make sure it wasnt model specific. i'll unplug it and see what happens.

 

[dbanbery]

right,

the other week i unplugged the air flow metre and the car was extremely sluggish, not desimilar to how it performed with the old air flow metre in. its plugged back in now, and recently stopped popping, and just being sluggish.

i'm getting the correct AFM. i still have the old one so i am going to get the number off that and get a replacement.

 

[dbanbery]

just another note, i had a replacement BOSCH MAF installed on my car and had a full reset with the correct machine. when the MAF is unplugged it did store a fault code on my memory. there was also a fault on the Lambda sensor, however i had it all cleared and it has been a lot better - still not perfect but its better. going to get my Lambda sensor replaced next to see if that helps at all. its better though. sluggish when cold and if you try and push it when its cold it wont go like it does when its up to proper temperature. it actually seems to get better with use through a journey, and doesnt get as hot so quickly in traffic either. bit better on fuel too i think.

there still is a slight hesitation and it has popped once or twice, but in no way as provocative to do as before [i could make it do it before]

all in all, a lot better. dont bother with intermotor MAFs is the lesson.