Problem after getting mafs repaired!?

[Cook0310]

Hi guys,

Recently had my maf sensor repaired by ecu testing in extremely quick time (highly recommended) as the car couldn't build up revs to leave first gear and diagnostics showed maf fault.

Anyway put the maf back in today and had the bad/esp fault light as they said it would so got it off by cycling the ignition as they said etc.

On test driving it the throttle seems to lack any response after changing gear or if needing to speed up quickly. It seems more of a gradual process rather than instant how it used to be. Idling from cold is poor but after a few goes it seems to settle. When I do manage to get some response from the accelerator it doesn't sound too healthy (sounds harsh on the exhaust)

I also changed the air filter itself when I got the maf repaired.

Could anyone suggest anything? Could it be lambda? Fuel filter? Dirty throttle actuator? There is no lights whatsoever on the dash anymore only the airbag one which comes and goes. I hope it isn't the fuel pump as it sounds a pain to change. Pressure comes from cap when opened and fuse seems fine but I haven't got a meter to check its exact pressure.

Will connecting it to a computer show something?

Much appreciated.

Thanks

 

[whitenemesis]

No point guessing, get the car on STAR and check the error codes.

How much did it cost to repair the MAF? Surely can't be cheaper than buying new?

 

[Cook0310]

£158 through ecu testing and was back with me in three days. Great service.

Would fault codes show if there are no lights on the dash?!

 

[nokia]

a new one would cost that much surely?

 

[Cook0310]

Nope merc I think quote £1400

 

[Howard]

MAS / ECU monolith on the w168 is one item. Coded to the car , so secondhand ones are no good.

Hence why people get them repaired.

ECU testing did ours 4 years ago ( cost a lot more than yours did too , which seems weird ) and the car has been perfect ever since.

Did you refit it yourself ? Make sure 100% that the multi pin connectors are seated properly and you haven't bent any as they are fiddly.

Fault codes would indeed show without lights on the dash. A faulty MAS won't put up a BAS/esp light though , a brake light switch would though ( new brake light switch is about a tenner , and solved the same problem on ours )

Reset them all ( on a star , not a generic code reader ) and go for a little drive , then read them again.

SRS light is likely to be the connector under the passenger seat , or the seat occupancy sensor itself.

 

[whitenemesis]

Thanks for the clarification Howard

 

[Howard]

No , no confusion.

The MAS ( mass airflow sensor ) is part of the ECU on the w168. It's not interchangeable on its own like every other mercedes !

Current MAS / ECU price from MB for the w168 is approx £1400

 

[Cook0310]

Hi Howard,

Yes I put it back in myself very carefully. I'll check again tomorrow but it didn't start first 4/5 times after it was refitted anyway?! When I had codes read last Sunday only the maf came up as a problem so I'll get it re-read tomorrow with hope that has some info.

Thanks a lot for your input.

 

[nokia]

Didn't realise you had an a class. We had a w168 1.4 petrol.

Have you seen aclassinfo.co.uk?

 

[Cook0310]

Yeah it's off there I got the maf details. It just worry a me now that it's still not right after repairing the fault. The main fault has clearly been fixed though as EML is no longer on.

Like Howard said I'll get it re-read and see if anything comes up. Planning on changing fuel and oil filters along with lamda front n back anyway as it's approaching 100k.

Yeah mines a w168 1.6

 

[Howard]

Does it 'stutter' when you put your foot down in first or second ?

Tick over ok , but when the car is under load ( not just revved while stationary ) it judders ?

We had this with ours and it was the coil rail. As per most other things on the w168 , nothing is simple , most cars have coil packs that you can swap out singly. No so the little a class , you have a 'rail' that connects to all four cylinders !

Anyway , new rail sorted our juddering.

You might be best to give the chaps at Forrera ( www.forrera.co.uk ) a buzz Monday as they really know their onions when it comes to the w168 and they happily advise over the phone too.

 

[Cook0310]

Hi guys,

Had codes read and p0170 came up so got ecu testing to recheck and it's not a problem on the ecu itself any ideas what else it could be?

Thanks,

Andrew

 

[Howard]

P0170 - Fuel Trim ( Bank 1 )

No idea what this means though.

 

[Alex Crow]

Has the boot strapping been reset?

 

[Cook0310]

I have no idea mate? How would that be done?

 

[Howard]

We didn't need to bootstrap ours when we fixed it , but I have read that it needs doing on some , good point !

A competent Indy should be able to do it.

 

[Cook0310]

What is it Howard?

Anyone know how/where I'd connect a pressure valve to check fuel pressure?

Cheers

 

[Alex Crow]

The pressure test connects to the O/S end of the fuel rail, but a tester will cost more than a fuel filter.
In fact, if you must DIY it and are looking for a good guess, change the fuel filter for a Bosch, Hengst, Mahle, Knecht or Mann filter.
Never use Coopers, Unipart or cheap brands, as they often lead to fuel pressure regulation issues, giving running faults.

 

[Cook0310]

Changed the lambda sensor today (apparently theres only one on the 2001 model?) and no improvement.

Mobile mechanic that came to do it said it can only be one of two things now - coil rail which seems an easy change or the throttle body?!

Any thoughts on this guys? Howard i see u had the coil rail changed, mechanic told showed me how to change it and seemed pretty easy? One cover and two 10mm style bolts that need to be opened. Are we talking about the same thing?

I hate cars!!! Haha

Cheers