Poor running 98 V70R
 

Recently acquired with more teething problems than I had hoped for !

Undid the MAF sensor and she starts but rough on acceleration

Replaced with engine running and she immediately stalled

Started immediately

Disconnected MAF and still running rough

No fault codes logged

No discernible change in misfire when disconnect spark plugs individually

This is not a hassle I have previously faced so any suggestions much appreciated, or from the above can I isolate the problem down to cleaning / replacement MAF required ?

unplugging the maf reverts the ecu to "safe mode", so it'll overfuel, but will usually run smoother, and the turbo should spool up nicely without hesitation as well...

can you please give a bit more information?
any more symptoms? rough idle, hissing sounds under the bay? oil level/oil change to see if its clean or mixed with coolant?
What I've noticed, that if there is no error code, sometimes the ecu doesn't registers one of the sensors, or it is purely mechanical.
I would still suggest to go around with a spray bottle around the air ducting, as it sounds either way like vacuum lines, throttle body or the engine is losing pressure... maybe a pressure test?
if it is not air related, then cleaning the injectors/fuel lines/fuel filter might be a good idea...

but it is poking in the dark right now with just this as information.

one thing you can do, start up the car, and smell the exhaust, if it runs lean or rich (if it runs rich with maf undone, then it should run okay with maf plugged in, so the fuel side should be ok)

also... I've read, that you disconnected the spark plugs... BUT did you check them? maybe new spark plugs? when ive bought my c70t5, the maf was dead, so when i replaced the maf, ive replaced the plugs as well, as they were RUSTED!!!

thats why we need a bit more of a description, as ive listed up any possible problem with the engine
edit: anything possible but the head gasket...

Thanks Reds

I have taken the plugs out and I would say they have only done a few thou.

There is no water/ oil mix and the sniff test I did on purchase was negative

I realised a long time ago that when I am under relentless pressure I can be extremely stupid. Given I have a T5 and and R running the identical block why not swap out one of the known working MAFs ?

Stupid Boy !

Hoping to do today and will post progress

My old T5r used to eat plugs and leads some time before the suggested replacement interval, the only time it ran rough was down to that.

true, all volvo mafs are the same (same part nr as well) until up to 2001, and after 2001 the mafs are doing the exact same job (same resistance, but done with a different material, ecus know their "good" values, the maf only gives a resistance value to the ecu), just more reliable (my 2000 t5 had old maf messing around when i bought it, and the new 2001+maf was a direct replacement... also 70-80quid for unopened ones on ebay, dont stress yourself buying 300quid maf (that is the old one anyways) from ECP)

so no gasket, but if the car ran good/lean with maf plugged in, i would check on the fuel lines, or at least change the fuel filter?
edit: as i assume, that your maf was shot from the start...

Thanks chaps for suggestions

Update
Changing to known in full working order MAF has made no difference :

Poor running - feels similar to running in 4 cylinders but spark sound on all 5 and similar strength

Hooked up VOL FCR and live data shows

Fuel pulse 13 to 17
Revs at idle fluctuate 800 to 864

4 x fault codes on 4.4 including ;
Vehicle speed signal missing - cl 221
Engine speed rpm signal faulty - cl 124

I know the dis needs replacing - coming Tuesday and genuine bouch leads already in the boot but any other suggestions welcome !

I know its not fly-by-wire, but if its air related then throttlebody? Fluctuating idle, poor running... Symptoms of an electric throttle body malfunction... Might work with cabled ones as well... Does it work better if you stay on the throttle a bit, keeping the flap open?
On the other hand... Check injectors (one might be clogged?) , fuel pressure regulator, fuel filter... Worst case scenario fuel pump... Since you said it didnt run rich, id start to think about the fuel side due to the throttle body would make it run rich/er

Edit:does vol ecr shows pedal positions and etc?

Maybe an ecu reset? If that doesnt cleans the rpm signal then some sensors need replacing...

Edit2:damn i had it so much easier...

Edit3:holy crap ure in london! How do you justify doing <20mpg in town? I know im power hungry, but i can barely justify doing 17mpg w my t5 in london...
On the other hand, vol fcr might help me sort out my non-working cc

Edit4: i promise ill stop after this... But... Just but... Isnt the car out of timing? Misfire without misfire, unstable idling, sensor misreads... Adds up... Kinda...

The codes point to the crank position sensor. Plugs in to a connector near to the cam sensor connector and bolts into the top of the gearbox with 1x bolt (10mm from memory).

Thanks chaps

I know we are all stabbing in the dark but every little helps

Ultimately I am confident it is fuel or sensor or both related, we will not give up and eventually get there !

Asch

What makes you think crank PS ?

My recollection on reflection is that if this is faulty the classic symptoms are non start ? Which I do not have she starts on the button every time - albeit limited given I have a knackered alternator as well, just to add into the mix !

And Skies most of my driving is non London- breaks my heart to get 19mpg when you can almost fly out of town and still return 26 !