Air flow meter fault, symptoms

Air flow meter.

I have written about this before in another post but have decided to write about it in its own right. I'm talking about a faulty air flow meter. The best way to find this fault is with a test drive and to listen very carefully to the driver's description. It is no good sticking the vehicle on a computer because as lots of you have discovered it does not show up in the fault codes. Have any of you wondered why? Finding this fault is down to good old mechanical detective work.

The symptoms:

In the initial stages it is quite subtle. The van starts and runs as usual and drives off as it should you then notice that you are having to use a bit more throttle than you used to get out of the turnings; this may go on for some time. Next, in the ebb and flow of traffic the van is not picking up as it should, almost sluggish in the way it gathers speed pointing to a possible turbo problem or a worn clutch in some cases. Finally driving away from a stand still is almost impossible! You have to push down the accelerator pedal a lot just to get up any speed to change up to second gear. On lifting your foot off the accelerator pedal to change gear the vehicle speeds up while you are changing up. On pressing down on the pedal again the van struggles to gain speed. It feels like it is holding back, this is because the air flow meter is not telling the 'brain' the airflow has increased.

I'm sorry to say changing the crank sensor will not do the trick but what is a good idea is cleaning the ERG valve because it will be close to being blocked if the vehicle is being used for a lot of stops start. The combination of these two things will make it purr like a kitten.

Vauxhall Vivaro rear hub nut and brake dices replace

This post has been prompted by the lack of good technical information out there on the Vauxhall Vivaro, Primastar and traffic van and in particular the rear hub settings.

I recently had a rear hub bearing seize up, luckily the bearing had not welded itself to the stub axle. Which is all too common in this type of bearing failure.

I am surprised and concerned to find a lot of miss information on forums. The lack of this information is making a statement like: “if you don't know the torque setting for the hub nut just tighten it up as tight as you can and then put a scaffold pole on the Tee bar and do it up some more!”. This stratagem can be dangerous and will cause the bearing to prematurely fail again. Why? The rear hub bearing is of the taper roller type which means that if you do not set it up correctly it will bind on the runners causing it to overheat and seize. These are not like ball bearings which can be over tightened (which is not recommended) because there is not the same direct affect.

The specialist kit you need to do this job properly:

36 mm socket

1. A thirty-six-millimetre socket for the hub nut. Which is three quarter inch drive that you may step down to half inch.
2. A Tee bar.
3. An extension bar like a scaffold pole no longer than a meter for loosening only.
4. A torque wrench that can go up to three hundred Newton meters. Which are not that expensive. Please note that wrench is Six hundred millimetre long (half a meter) This is the optimum length for this weight of tightness.
5. Spanners and or sockets for the brake calliper mounting bolts of twenty-one millimetres.

300 Newton meter
torque wrench

Destroyed bearing.
Also shows ABS ring.

Be careful not to damage the wheel sensor. The hub nut should be tightened to two hundred and eighty Newton Meters which is surprisingly not that tight - about a quarter of a turn or so after it has been done up normally with a ratchet. The mounting bolts for the calliper cage- one hundred and eighty Newton meters- you should clean the threads with a tap before adding new thread lock and the wheel nuts are one hundred and forty Newton meters and don't forget to put a little bit of lube on the threads.

If you would like to ask any questions or add further to this post, please do.

Related post:   Sticking handbrake.