Hi,

bought new MAF (and eventually replaced it 6 times within a week!) due to p0102 error happening every now and then (once every 2 or 3 weeks).. anyway, the maf is verom vdo (siemens) and bought from a well known maf shop.. when i look at the new maf reading.. at idle it shows on avg 1.8 g/s and at some moments i can see it go as low as 1.08 g/s .. the max is 156 at WOT..

now, there is NO maf errors (or any other error), but when the car goes into operating temp (80c) after driving, when i stop and put on P or N, the rpm raise to 1.4K and keep steady there until i turn of the car and turn it on back.. if the A/C or high beam are on, the RPM will stay steady at 800 when i put on P or N!!!!!

The rpm in other situations is stable, some rare ocassions, when the car is warm and i turn it on, i see it fluctuating -+50 and the car hesitates very little, and this disappears if i put on D and drive the car.

checked form vaccum leaks (with wd40 spray) only sprayed around the air filter and maf and under the filter (in case of the 12$ hose!) and nothing with revs changed whatsoever! - didnt spray on the EGR or under bullys just in case the area is hot and goes on fire! but inspected by eye and all lines look like brand new!

checked the connections, all look clean and sparky! and just in case sprayed them with elec connection cleaner..

when i checked obd2, i can see that when the car goes into close loop, it gives within a min closed loop - FAULT. but i cant see what the fault is!


Car: w209 European (same as w203 engine) clk 2004 1.8L petrol kompressor M271 Engine. car is only 40k miles and very little driven, well taken car of.. new spark plugs (after the issue arise), air filter is getting changed every 2 months as a prevention for maf damage..


what i noticed also, that after changing brake pads, the car braking is not as usued as to be.. a small touch on the brake pedale is enough to hold the car.. now i have to press too much (as if i was driving my grandpa pickup!) the pedal has the same feel, but not same perofrmance -- not sur eif this issue is realted to the above isssue or not!


any help is appreciated!

any advice?

 

wow.. 125 views and not even one "sorry for you" :-)

 

WSE ,Can't help you with the MAF. but take a look at this site for breaking in your new pads. http://stoptech.com/tech_info/wp_bedintheory.shtml

Good luck , let us know how you go with both problems . Carsy

 

Thanks carsy, Will make sure to update you when I find a solution..

 

I noticed that sparkadv is flucuting very high and very low making the car shake while the rpm look steady!!

attached the saved log for pcmscan: http://www.2shared.com/file/bt7xwHrv/banana.html

 

WSE,
I have read on this forum that disconnecting the MAF may give some help in fault finding.

Try the search tab top RHS

 

I already disconnected it and ran for 5 days with no high idle and car was running perfect (at least better than maf plugged) - only difference, when maf is plugged, the car kicks in faster at roundabouts and so..

now, there is no way that 6 mafs to be dead.. all are original and all are new and from wellknown german only-maf-biz

the results here are from this morning when p0102 was set with p1072 (came later)

https://mbworld.org/forums/attachmen...reez-frame.jpg

and

https://mbworld.org/forums/attachmen...rror_codes.jpg

 

Please do us a favour. Check the MAF part number on the black plastic cover on the MAF to ensure it is a Mercedes MAF. A VW/Audi MAF looks identical but will not work on a Benz.

You have to ask this question if it runs well with the MAF unplugged on a default engine map.

 

the maf part is correct - checked it more than 10 times before i order and after i ordered a genuine merc maf (only supplied by VDO siemense, 500 USD)

The car runs very well on normal operating temp when maf is unplugged (at least no high idle, and a very unnoticible hesitation)..

I noticed a small hssss noise when the car was idling and my ear on the throttle area (there is some strange electric device on top of it, i think the hsss comes from there) but sprayed on it nothing in rpm or engine changed!

the high idle only happens if i drive the car when normal operating temp and then put in park, all others including cold have no high idle.

I already unplugged the maf, and it idled perfectly, but also i already changed 6 mafs (originals from siemens) and all did the same! when i put an ebay cheap maf, it idles fine!! can all these 6 are defected? noway!

 

Grasping at Straws.

Is there a module which increases fuel/air (throttle) when the engine has the a light load at idle. You say all is well when the headlights or A/C are on at idle.

Maybe this "Module" is not decreasing the throttle when they are off.??

If it was a carburettored engine I would say that you have a slight air leak to the carb. Have you been around & checked all hoses & run around & tightened everything up.

Good luck.

 

I think its managed by ecu, that changes to the higher load table (which is usually pre-set table that wont change or get affected by anyother factor).. I tried to think about what modules affected it (like icv,.. etc) but digged in everywhere and they say my car has no such things! - info over internet can be extremely misleading and can cost more than bringing to dealer (who said originally, I HAVE NO CLUE when i told them the symptoms!)

the car is EFI and slight leak wont change the rpm because the ecu is very fast to adjust, so you will barely notice unless the leak is massive which will make the rpm fluctuate up and down.

when i unplug the maf (while idling high) it returns to normal idle immediately... i just put cheap *****e chinese banana maf and it idles perfect, but performance wise, car is lada 1980!

ps. when the car was idling at op temp, i unplogged oil dipstick, and nothing changed in idling at all.. what does that mean? this should be considered a leak, but nothing changed in my car! not even a cel (kept it unplugged for 5 mins)

 

How old is the battery ? Is the AVR operating correctly ? Alternator about 14.5 volts above idle ? I have seen weird happennings on this forum which are caused by a weak battery.

More straw grasping !!

 

yeah, this came to my mind - will check today when i leave my job.. i think i can check through dashboard.. battery is anyway 7 years old now, but when i travel and leave the car parked over 30 days, i can ignite it in just one switch on.. will keep you updated

thanks carsy!

 

You are very much mistaken, the ecu is not designed to compensate for air leaks its designed to use the infomation it recieves from the sensors, now if you have an air leak which is very common on a 271 engine, the airmass value will change so the ecu will make different load calculations. which will cause all sorts of running faults. your airmass should be around 2,2g/s at normal idle speed with no load (ac off), check your crankcase ventalation hoses. they split and suck air right under the airbox at the throttle body.

 

Now Im more confused - i have been told 3 totally different g/s for my engine.. some said min 5, some said 3.3 and you say 2.2 and science say its a rule of 1liter = 1g which ends up 1.8 g/s - und currently my car goes on 2g/s on average, but sometimes dips to 1.08 g/s and one moment it got 0 g/s for a second! <-- at that moment, the car never shaked!

checked the partial load vent hose and its fine (not same type of house went on american cars.. it was already enhanced from factory when the car bought)

i unplugged the dipstick and didnt feel any difference when the car idled.. not even a cel (so i though a leak may not give any difference if its there, so more doubt about having a leak.. the question is, how to professionally and correctly and easily cehck for leak.. apart from dealer way!)

thanks

 

Using genuine Mercedes diagnostic equipment, on a 271 engine that has no problems you will see around 8kg/h airmass with no load that is lights off ac off and steering straight ahead. at operating tempreature around 90 deg C . what diagnostic tool are you using when you see these airmass values drop off to zero?

I have fixed plenty of these faults and i can tell you the first place to look on a 271 engine is those breather hoses for the crankcase and secondly check the valve timing.

that car has a very long intake tract it can leak anywhere, the correct way is a special tool which prssurises the intake to about 300mbar then you listen for leaks.

 

Agree any vacuum hose leak, EGR leak, ECCS/purge valve leak, captive crankcase ventilation leak etc. will throw you out.

 

what is valve timing?

I see a forth number for mass readings now! which is a lil bit more than the avg i get.

I just plugged the chinese banana maf and drove in traffic for 2 hours with a/c on and a/c off and i can say safely no errors, and idles very fine - performance is ****e (response isnt the same as the genuine part)

i use generic elm with pcmscan and it rarely drops to zero but backup to normal reading within a second.. did that twice (while making random drive scans) - and got the p0102 both times.

yeah, the professional machine.. which my area lack of! i wish the english can learn from the americans on how necessity is a real mother of invetion!

 

forget about using chinese or aftermarket parts, airmass sensors are critical sensors use only genuine parts... your scan tool could be giving you false readings (like dropping to zero) at times.

Valve timing is the relationship between the crankshaft and the 2 camshafts, and they are mechanically timed with a timing chain.
On a 271 engine the cam gears wear and the chain can jump a tooth, or the chain stretches retarding the valve timing to the point where it affects engine breathing.

things like air leaks and valve timing will all affect the airmass values. the ecu will try to compensate until a "mixture formation at idle speed" end stop is reached then a fault code is usually set.

once you repair your air leaks the control units mixture adaptation should always be reset back to zero.


BTW. 8kg/h is 2.2g/s

 

+1

Another thing to check is the throttle body. The plate actuator can either develop oscillation or become sticky. This does not usually throw a code/CEL. Cleaning can help but usually means replacement. Also do a throttle reset for good measure. See stickies for procedure.

Your MAF still worries me but you have tried so many I think we can forget about it being that.