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.

Vivaro couldn't pull the skin off a rice pudding.

The van has developed a running fault that started a month or so ago and has become progressively worse. It has taken us some time to chase down the cause of this problem.

The symptoms:

 This fault shows it's self when you drive away from a stand still. You have to push down the accelerator pedal a lot further than is normal to get it to speed up enough 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.

 

Thought process and action.

 

This suggests that it is a fuel problem. But it has nothing to do with fuel, injectors, high pressure pump, fuel filter or related sensors. Another suggestion was the turbo, but we could hear it spooling up. We checked the turbo pipes, ducting was tight and not blocked. We found a couple of lose hose clips but not enough to cause power loss. Also checked to make sure the waste gate solenoid worked as it should.

At one point we thought the ECU needed a re-boot, again it did not seem likely. Thinking about it, it was a flow problem the only other thing that came to mind was the air flow meter. Before we paid out on a new meter we surfed some motoring forums for pointers, but no one had this fault it would seem. We came across a thread that suggested the changing of the airflow meter would sort it out, but this gentleman also had the crank sensor replace. After a short discussion we decided to go with the air flow meter. Bingo! got it in one and what a relief, it would have been an expensive mistake otherwise.



Air flow meter

 

Extra work.

 

While we had the air filter housing off, which is a pig remove, we thought it prudent to check the glow plugs as it only takes a couple of minutes with a voltmeter. We found that two of the plugs didn't work. The ERG valve drew my attention because the inlet manifold was covered in oil suggesting the gasket had failed or the bolts were loose. You have to be patient when removing it as it has a build-up of oil residue. On removal, it was found clogged with a thick coagulated oil that took a bit of cleaning up.

 

It runs and pulls like a train now. The rice pudding skin doesn't stand a chance!