Engine 850: B5254S/2.4/20v: car won't idle with MAF plugged

[wwatu]

Hi,

I have a '96 year volvo 850 2,5L and 125kw(170hp) Saloon.

Have a few questions tho, when I plug in my MAF, the car idles like this:

https://www.youtube.com/watch?v=IfLNxWGZAWY

Without MAF it runs much smoother, but doesnt idle very well either, bogs out usually after a while, when braking etc.

Video:
https://www.youtube.com/watch?v=Z3v6z40TvHA


So my question for you is do I need just a new MAF, or do I have a vacuum leak somewhere,TPS is faulty, faulty AIS or lambda.

One more question though, do the DIY led error code readings can be done with this model?

Thanks in advance!

[Tension]

With the MAF unplugged, the car goes into limp mode. The problem is not the MAF. Read the codes.

[wwatu]

Originally Posted by Tension

With the MAF unplugged, the car goes into limp mode. The problem is not the MAF. Read the codes.

Alright, but does my model support led error code reading?

[Tension]

Yes. You will need to build your own reader. All you need is a 12v LED and optionally a push-to-make button. Schematics are available online.

[wwatu]

Originally Posted by Tension

Yes. You will need to build your own reader. All you need is a 12v LED and optionally a push-to-make button. Schematics are available online.

Alright, thanks, tried 2 different diagnostic tools today, neither of them worked, last chance is tomorrow, hopefully get a proper diagnostic, if not, I'm going to try the led method.

[Tension]

Don't waste your time. The 850 doesn't support OBD-II, it just has the connector. It's the LED method or nothing I'm afraid.

[scutyde]

96 20V either have the LH 3.2 which has 2 ECU which can be read with led or the Motronic 4.4 which can only be read with Sotware (VolFcr can for example).

If the car runs better without the MAF then your MAF is shot. And starting from 96 the 850 supports OBD II (except ECC, Cruise, Motronic 4.3 from turbos and Fenix )

[Tension]

Originally Posted by scutyde

If the car runs better without the MAF then your MAF is shot.

That's bollocks

[scutyde]

Ok my bad answer was not complete:

So the 20V engines are very allergic to air leaks . If you have one and the MAF is good the engine will play up and most likely throw a MAF error as it will notice that something is wrong. A common problem is the big hose from the air box to the throttle body. This will explain why the car runs better with the MAF plugged out as the car substituts the values. So check that all air intake hoses and the small ones are intact.

If there are no air leaks and the car runs better without the MAF then the MAF is faulty. Again the engine management will substitute the MAF values (I presume according to the throttle potentiometer and MAP sensor (if one is fitted).

As far as I know the LH 3.2 will not run without a MAF so I think most likely yours is a Motronic 4.4.
You can easyly check by counting the number of ECU's in the big black box near the washer reservoir: 2 for LH 3.2, 1 for Motronic and 1 for Automatic if car is an automatic.

[wwatu]

So, finally got my hands on yesterday. Finally have time to update.

So.

First of all, I think it's quite clear what's the problem, at least hopefully it'll fix it totally when replacing MAF.

It looked like this when I unplugged it:


Second thing, I wanted to ask is that if there's something missing in my fuse/relay box:



Had 2 ECUs


Also somehow had oil around the spark plugs which I cleaned up:




Also wanted to ask which oil should I use in my engine, everywhere I hear different types I should use, so can't really decide. In the winter it gets up to -25C in severe cases and summer +30C.