Intermittent misfire 1998 E280

[t15dja]

Hi,
I wonder if anyone could suggest what might be wrong with my 1998 E280, 35,000 miles.
I'm experiencing an intermittent engine misfire from start-up about 1 - 2 times per week. No particular pattern to it - just seems to happen at random. No warnings on dashboard. Problem doesn't go as engine warms up but if I stop the engine (cold or hot) and restart it the problem usually disappears.

When its happening the car has no acceleration and idling is quite rough - seems like it isn't firing on all cylinders. Car has FSH and all spark plugs were replaced about a year ago.

Don't understand why should a stop and restart clear the problem?
Thanks in anticipation

 

[Shude]

Anything that works after a restart like that is probably a sensor. In this case I'm thinking Mass Airflow Sensor (aka MAS) or the crankshaft sensor/sender, although the latter is usually more predictable.

The MAS is a common fault and is almost considered a consumable or regular service item on some models!

If you search the forum you will find lots of threads about this

 

[Dieselman]

ditto

 

[t15dja]

Price for a MAS

I'm just recovering from being quoted £280 by the local stealers for a new MAS for my 1998 E280!!!
Can anyone tell me if that's the going rate or can they be bought at a more sensible price elsewhere (and if so where)?
Thanks in anticipation

 

[1001graham]

I had a similar problem on my E320 although mine was anything above 3-4000 rev's. I was recommended to change the MAS and wow what a difference. Not only cleared the problem but the car is so much more responsive and fuel efficient. Not saying it will fix your problem but if you want to give it a try I got a replacement from http://www.airflowmeters.co.uk for £91 +VAT including free next day delivery - better than the £250+ quoted from the Merc' dealer.

[FONT=Arial, Helvetica,
sans-serif]www.airflowmeters.co.uk[/FONT]​

 

[t15dja]

A happy ending!

Well....replaced the MAS yesterday (a doddle to do by the way - just one jubilee clip to loosen and the air filter box clips to undo) at a cost of £183 from GSF Carparts (www.gsfcarparts.com) for a new Bosch item (same as the original factory fit).
This was nearly £100 less than the stealers so I was very pleased with that, but I see 1001graham has got one for even less (see thread above). At the time of purchase still felt that was an awful lot of money for a small black piece of plastic and a few wires (but read on.....!)
Car now appears transformed! - very willing to accelerate and revs eagerly ! Amazing what difference that small black piece of plastic and a few wires has made!
I'm surprised how I'd got used to what had become increasingly dull performance - until the recent misfire problem brought things to a head.
By the way the new MAS has also solved a problem I was having with the autobox. I didn't mention that in my first post above because I thought it was the start of a totally unrelated problem.
Gear changes were becoming decidedly irregular and un-smooth, with a definite surge in revs between gears 3 and 4. All that has now gone with the gearbox working as smooth as ever. Not sure how the MAS influences the performance of the autobox, though - perhaps someone could advise.
So, if anyone is experiencing the same problems as I was, i.e. lacklustre performance with occassional misfire, and confused autobox performance, you would do well to consider replacing your MAS !
I'm so pleased I'm going to go out and give the car a damn good cleaning !

 

[t15dja]

P.s.

Thanks to Shude and Dieselman for suggesting the MAS (didn't know of its existence before !)

 

[Shude]

Thanks to Shude and Dieselman for suggesting the MAS (didn't know of its existence before !)

Glad to read that it's sorted!

 

[Dieselman]

I'm so pleased I'm going to go out and give the car a damn good cleaning !

We normally refer to this stage as a damn good thrashing

Yup the MAF will affect the autobox as it tells the ECU how much air is being drawn by the engine so the load and trottle position is calculated accordingly.