MAF Sensor - replacement/cleaning

[GreenMachine]

I'm trying to fix a lumpy running problem, I've changed my rotor arm and dizzy cap and improved things alot, but I picked up a spare MAF which came today, I popped it in - a bosch 0280217107 which so far as I can see is the right one for 20V 2.5 but on trying this one the car starts and cuts out, remove the connector the car runs - of sorts - put the old one back following wiping the "leaf" with a cotton bud - I haven't got any alcohol cleaner yet! and the car seems to run a little better.

Is the MAF I picked up dead?

and how bold can I be with the MAF cleaning before I have a spare on standby? - I've found more info about this now - guess I need to get down to maplins and get a working spare first!

Carl

[Niles]

sounds like the replacement maf is dead sir.

[M-R-P]

As above. I clean my MAF with half a can of carb cleaner. In short bursts so you don't get it too cold. I'm not brave enough to use cotton buds or anything - they're bloody expensive lol (the MAF, not the cotton buds).

[rockheadrumble]

Have you disconnected the battery since youv'e changed the MAF? when you diconnect the MAF the car should revert to a in built map so the car still runs if the MAF fails.

If you put the MAF on when the car was switched off then it should return back to the normal map automatically but it would be worth disconnecting and reconnecting the battery after the new MAF is on.

Joe

[GreenMachine]

Have you disconnected the battery since youv'e changed the MAF? when you diconnect the MAF the car should revert to a in built map so the car still runs if the MAF fails.

If you put the MAF on when the car was switched off then it should return back to the normal map automatically but it would be worth disconnecting and reconnecting the battery after the new MAF is on.

Joe

Funny you should say that, I did disconnect the battery, she is running better, but was that just resetting the map?

I'm expecting a replacement spare tomorrow so I'll have an update then.

[rockheadrumble]

It will go back to the map thats stored in your ecu when you reconnect the battery. so if its mapped or standard it will go back to that. On my car (940) it will go back to the standard MAP but will then adjust it self slightly because it is self learning and can't be mapped.

When the maf is diconnected/broke then it doesn't know how much air is getting in so it uses another MAP to cope which is why it runs with out it but not very well. Im guessing it will rely on the 02 sensor or the revs for how much fuel to inject but i could be wrong.

[GreenMachine]

It will go back to the map thats stored in your ecu when you reconnect the battery. so if its mapped or standard it will go back to that. On my car (940) it will go back to the standard MAP but will then adjust it self slightly because it is self learning and can't be mapped.

When the maf is diconnected/broke then it doesn't know how much air is getting in so it uses another MAP to cope which is why it runs with out it but not very well. Im guessing it will rely on the 02 sensor or the revs for how much fuel to inject but i could be wrong.

OK, so taking data from the cam sensor, flywheel sensor, possibly an internal clock, the lambda sensor(s), and the MAF, is the ecu constantly learning to change the timing advance/retard and fuel/air mixture at differing revs to provide effective running, have I missed any sensors?

So if any of those are faulty/dirty this throws out the system/ecu, holes on the inlet system, blowing on the exhaust manifold would have the same effect, as each sensor must measure everything its supposed to to return the correct reading, effectively everything must be right for this type of system to learn properly so to speak?

[rockheadrumble]

The ecu won't change the timing as there is no way of doing that unless you do it manually. But it will certainly change the fuel/air mix, that essentially is what the MAP is all about. I think the cam sensor will tell the ECU whan to inject the fuel.

I forgot to mention earlier that a good way to tell if the MAF is nackerd is to disconnect it whilst the car is running, if the idle changes than its a good indication that the MAF is ok as it is changing from one MAP to another.

I recently thought mine was broke because it was boosting really bad but when i disconnected it at idle the engine change was very obvious.

joe

[GreenMachine]

The ecu won't change the timing as there is no way of doing that unless you do it manually. But it will certainly change the fuel/air mix, that essentially is what the MAP is all about. I think the cam sensor will tell the ECU whan to inject the fuel.

I forgot to mention earlier that a good way to tell if the MAF is nackerd is to disconnect it whilst the car is running, if the idle changes than its a good indication that the MAF is ok as it is changing from one MAP to another.

I recently thought mine was broke because it was boosting really bad but when i disconnected it at idle the engine change was very obvious.

joe

Joe thanks for the responses, I've never tried to get my head around electronic everything before, dizzy's of old used to control the low tension side of the coil as well as distribute the high tension, obviously the 850 dizzy only has the ht side of things, so I was assuming the lt comes from the ecu, which is why I was thinking that the ecu could adjust advance/retard?

I also experienced the same change in idle speed when I disconnected my MAF so given what we're saying above what I'm thinking now is I might have a problem with either lambda vacuum or exhaust and given my mileage why not all 3!