Changed the Air Flow Probe

[Blackwaterslim]

I posted a ...er..post regarding my c200 and the general(and much appreciated) opinion was change the MAF so today (I had to save up) I bought a new probe and fitted it...well it has made a difference! the car does pick up and go like it is receiving fuel, if you hit the throttle it hesitates from standstill then picks up and behaves like a 2 litre should.....however, it is very lumpy on tickover at idle it hunts between 8-900 and 500 revs is now deff using much more fuel and is not as smooth as with the old one in? on the motorway I swear it is 500 revs higher than normal 80mph = 3000rpm
It fels like its tuned (showing age here) in the old days if you tuned up your old dizzy sparked motor it would be **** at low revs then go like hell as you pass a certain rev range.......any ideas?

Cheers
K

 

[alexander patie]

yep, you need the self adaptation resetting, or just keep going 'till it re-adapts. to explain, your engine's ecu has learned to adapt to the failing maf sensor. it has adopted long term self adaptation data. it is now using these correction values unecessarliy, causing poor running. in time it will adapt to the new sensor, or you could have it reset by a specialist/dealer as it should have been.

that is one possibility, others include the sensor being a poor quality copy of the genuine thing. assuming you have a petrol c200 it should probably be a bosch one, depending on age etc. there are other possibility too.

 

[Blackwaterslim]

yep, you need the self adaptation resetting, or just keep going 'till it re-adapts. to explain, your engine's ecu has learned to adapt to the failing maf sensor. it has adopted long term self adaptation data. it is now using these correction values unecessarliy, causing poor running. in time it will adapt to the new sensor, or you could have it reset by a specialist/dealer as it should have been.

that is one possibility, others include the sensor being a poor quality copy of the genuine thing. assuming you have a petrol c200 it should probably be a bosch one, depending on age etc. there are other possibility too.

Thanks for reply..it is a petrol (got sick of putting petrol in my diesel) the unit is made by Lucas? bought from reputable source, I have car serviced by MB tec he said to replace MAF...I just bought the probe only as the body it sits in (as far as I can tell is passive) looks new...in fact on inspection the old MAF looked very clean and new...the green o ring looked like it had been in place for only a short time..car had 80k on clock when bought. This self assesment thing...MB tec never mentioned that..

 

[Dieselman]

I'd be very suspicious of the new MAF. Get a Bosch one and it will probably run OK.
Another option is an air leak into the intake trackt or manifold or sticky throttle flap.

 

[alexander patie]

lucas did not make the OE maf sensor for your car. as diesel man suggests, get a bosch maf! as diesel man also suggests there are many other possibilities, but your idling was fine before that new maf sensor was fitted!?!?

 

[Blackwaterslim]

Right then Bosch MAF it is ...bought Probe from German and Swedish guy said was as good as? anyhow they look identical.
Will report on change £150 for Bosch unit thanks again

K

 

[Dieselman]

The pattern ones from GSF are rubbish, often the engine won't idle at all. Gina had problems with a new one bought there a few months ago.

There is a simple way to test the MAF using a voltmeter.

Start here:

http://www.mbclub.co.uk/forums/engine/67791-engine-missing-10.html

 

[Blackwaterslim]

Well have to admit I seem to be a chump! everyone who gave advice said go for Bosch so it was a Bosch one I ordered...£145 complete unit...the body on mine is fine so asked if I could just get the probe...no problemo said GSF dude, and produced said unit £45 made by Lucas. Now WTF is he doing ? if Lucas do not make the part and it is for another motor...plus if the yare truly rank why sell em? so now I am going to get a Bosch unit £150 which means I will have spent £200 AAAAARRRRRRGGggggggg...it was never like this with points and a carb. Had a good look at the probes...they do look identical....and pattern one is in Lucas box and packageing.......Thanks for help, wondering howc far up GSF dudes backside this thing will go.

 

[lynall]

As the new pattern lucas one is no good surely you can get your money back.
I bet they have had loads returned.



Lynall

 

[Blackwaterslim]

Changed Probe to Bosch and guess what...same problem...in fact same without it connectd...so I guess thats a sxxt load of money to prove the fault lies elswhere...now having garage bod do his fault code check ..he thinks the people that sold me the car removed the bulb from the engine maint warning light on the dash..I do not care anymore just want my car to work

 

[Dieselman]

Oops, you should've metered it first..
Check for air leaks into the manifold if not that it's likely to be the lambda sensor, though they don't often fail. You can test for that as well with a meter.

It's not just misfiring is it, as in a spark fault.?

 

[Blackwaterslim]

no new plugs and service. we put a code machine on it and it says (old probe..running lean, new probe running rich) Tech recons its the (as you have said ) the Lambda sensor ..so we are starting there! bloody hell what was wrong with points anyway! will keep you posted..I am sure its a really nice car..however I do look longingly at vectras and mundanos they cost less but seem so much less worry!

 

[alexander patie]

have you had the self adaptation reset like is suggested in post #2? have another read...

 

[Blackwaterslim]

yep, you need the self adaptation resetting, or just keep going 'till it re-adapts. to explain, your engine's ecu has learned to adapt to the failing maf sensor. it has adopted long term self adaptation data. it is now using these correction values unecessarliy, causing poor running. in time it will adapt to the new sensor, or you could have it reset by a specialist/dealer as it should have been.

that is one possibility, others include the sensor being a poor quality copy of the genuine thing. assuming you have a petrol c200 it should probably be a bosch one, depending on age etc. there are other possibility too.

There are other possibilities? do not like the sound of that!

 

[Alan M]

no new plugs and service. we put a code machine on it and it says (old probe..running lean, new probe running rich) Tech recons its the (as you have said ) the Lambda sensor ..so we are starting there! bloody hell what was wrong with points anyway! will keep you posted..I am sure its a really nice car..however I do look longingly at vectras and mundanos they cost less but seem so much less worry!

Did he actually tell you the codes he pulled that allowed him to deduce probes running lean/rich - btw which probes are we talking about the MAF or O2?
How has he tested lambda sensor - is he just using codes or has he actually tested response and output of O2 sensor? Does sound a little like he is going down the often expensive route of replacing parts on a guestimate basis rather than diagnostically testing in a logical process.
Have you, as suggested, had adaptive values reset since new MAF? "new probe running rich could be that if old one causing lean - ECU would have adapted to richen mixture - this could now be to the extent that it's now having difficulty bringing mixture lean enough.
Have you checked voltage output, (or Kg/hr if connected to diagnostic reader) of MAF at idle and higher rpm and compared to specs for your car?

As to Mundeos and Vectras being less hassle - all modern cars use the same basic components to control fuelling so have exactly the same issues. Also as they are cheaper owners often won't want to spend on maintaining them and I bet they are in their ex rep-mobiles wishing they were driving your Merc

 

[Blackwaterslim]

ha ha I would like to think so! well he did use the checker thing and apparantly the code was chucked out by the lambda sensor to say running lean...this code cleared no new codes...so I asked about the adaptive values and he said they were unlikely to need reseting for the MAF ? so he is going to have it back and check voltages etc.
Big thanks for you input
K