R129 SL500 MAF Sensor (1993)

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PhilvB

New Member
Joined
Oct 11, 2014
Messages
22
Location
Old Sodbury
Car
500SL
I have a misfire on my 1993 SL500 (R129). All indications are a faulty MAF. I have purchased 3 of these from breakers on eBay at great expense, and none have fixed the issue. It could be that I've been unlucky enough to buy 3 duff ones so:

1) is it possible to test a MAF, other than by fitting it to a car?
2) Is there a cheaper alternative to the Original Bosch 0 280 214 004 part?

Phil
 
Hi,
I presume that you have checked the distributors, leads and plugs as these often suffer from damp.
Have you had it on a diagnostic or code reader for any fault codes that could indicate a cylinder ?.
Hope you solve it.
Bosch MAF s should be fine, though not sure I would trust a second hand one. Unlikely all three duff but ???


Sent from my iPad using Tapatalk
 
Hi,
I presume that you have checked the distributors, leads and plugs as these often suffer from damp.
Have you had it on a diagnostic or code reader for any fault codes that could indicate a cylinder ?.
Hope you solve it.
Bosch MAF s should be fine, though not sure I would trust a second hand one. Unlikely all three duff but ???


Sent from my iPad using Tapatalk

Everything has been checked - even replaced the inlet and exhaust manifold gaskets. A Merc engineer said the code showed MAF sensor failure, but as I said, 3 of them being duff? Could be though.

I've heard of a lot of people having this exact problem and replacing the MAF solved it - after a long search for a siolution.

It's OK when cold, but starts to misfire once it gets warm.

Rgds/Phil
 
Are you still on the original wiring loom?
 
That would be my first port of call then, check the state of the loom insulation. The odds are it's totally shot.
 
On cold start the value from the MAF is somewhat irrelevant as the engine is running massively rich. How warm is warm?
 
So about the time taken for cold start cycle to complete?
 
That's about it. I travel from my house to Tesco, which is about 2 miles away, with no problem. When I return to the car, the misfire starts and doesn't go away.

Rgds /Phil
 
A mechanic friend has suggested the coolant temperature sensor, which is a cheap object and I'll try it.
 
Not impossible, but consider the following:

1) If the sensor was failing you'd see that as wonky readings from the temp gauge
2) If it fails completely it will generally fail "cold", meaning the car will remain in cold start mode which you're already mentioned does not seem to be a problem.
 

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