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.

Lane hogging becomes a road traffic offence

This is just a heads up. How you drive is up to you.  I am not sure who said this to me:. Ignorance is no defense in the eyes of the law.

This was copied from the ITV news so if you would like to know more click the link.


 2:46 PM, WED 05 JUN 2013

Middle lane hoggers to face on-the-spot fines

Drivers who hog the middle lane or tailgate other cars face on-the-spot fines of £100 and three points on their licence, under new measures announced today.

The fine for using a hand-held mobile phone while driving or not wearing a seat belt will also rise from £60 to £100.

Report by Amy Welch.

Handbrake fails MOT.

Handbrake adjuster

This is a stressful time for the motorist; it is where you hand over your pride and joy to a third party to be poked, prodded and shaken into revealing those profitable faults for the garage. If you are an owner maintainer you should be able to minimize these unexpected failures because you regularly service and put right problems as they show up. I know in practice this is not always the case. But it is better and more cost effective if you do, than to be thrown in at the deep end when you are at your busiest.

MOT testers are human and have pet hates. As an ex-tester mine were lights not working and torn wipers. To me this indicated that it may have other MOT issues which proved to be the case on many occasions.

Brake fluid

I am not immune from the unexpected. Having checked the van over and put right the sticking hand brake again, I was confident that it should

 pass its MOT. The van and tester had other ideas. It failed! I was expecting him to say it was a ball joint but no it was that damned hand brake again. Apparently, the brake machine showed that its effectiveness was outside the permitted balance parameters - (MOT speak), and it was the offside that was less effective or put another way the nearside was still sticking.

With the vans 'back end' in the air and the wheels off, I started to check everything again. But this time more thoroughly than before. I started by loosening the hand brake cable at the adjustment in the middle of the van. Then removed each cable from the calliper first checking to see if the handbrake lever was at rest. They were both holding off by a fingernails width even though the cable was very slack.

Surprisingly with this

poxy system this small amount can make the brake bind badly. I freed off the arms as described in a previous post.  Then checked to see how free the movement was on each hand brake cable that ran from the calliper. The OS one was very rough and stiff as the cable moved back and forth in the sleeve. The NS one was less so but on the way.  I changed both to be on the safe side. what's next? The brake pads are not that old, but I checked them anyway. The near side looked OK, and the piston moved freely the same for the offside, but the pads had an unusual wear pattern. It looked like the centre of the pad had crumbled away meaning that only the outer portion was in contact with the disc; could this be the problem? I checked the brake disc carefully; the surface was reasonably flat, and I could not see any reason for the centre wearing faster than the outer edge. The only way to be sure is to replace them. I know! more expense!

Now to fit them. I started by winding the piston back into the calliper. This needs a special tool but if you do not have one you can get away with using an adjustable wrench (the type that bites your fingers if it slips off - ochhh!!) and a G clamp. It is slow and a pain but saves on the price of the tool. Basically, you wind in the adjuster several turns and then use the G clamp to push the piston back. Before you start this, you should pop the hood and take the cap of the brake fluid reservoir and place a cloth over the top to stop the brake fluid pouring all over the engine bay. This may happen if the fluid has been topped up. Once it is wound back clean the mounting bracket area where the brake pad sits and then put a little copper grease on the edges of the pad that sit on the bracket, this prevents sticking. Push the calliper into place, always use the new guide pin bolt provided with the brake pads and tighten to 35 newton meters (26 lbf ft). You should only remove one pair of pads at a time this allows you to reset the piston for the new pads by pumping the brake pedal also reducing the chance of the fluid reservoir overflowing. Spin the disc to make sure it is free and then apply the hand brake with your hand on the lever to make sure it works and releases properly. Then do the same to the other side.

Adjustment settings

Now attach the hand brake cable to each side and adjust the cable. I usually put a bit of copper grease on the adjuster thread to stop it freezing. Wind the adjustment nut up until you obtain a clearance of between 0.1 and 0.5 mm between the operating lever and the stop on the back of the calliper body. You can check this by using a feeler gauge. Now spin the discs, if it feels like it is binding then back the adjustment off until it stops. Hop in the cab and pull on the hand brake several times checking how many notches it come up - one or two is about right but not set in stone. Then check again to see if the discs are binding now the cable has been settled in. If OK, it's time to box it up.

It is a tense time back at the MOT station as they check the hand brake on the brake machine. Has it passed? it looks to me as it's within parameters. Yes! A 'thumbs up,' great news! back to the day job. 


Update to post 18/8/13.

The handbrake is still working properly with no sticking to date. I have noticed that the mpg has increased since sorting out the brakes by as much as ten miles to the gallon which is astounding. So, all those bits I replaced will have payed for themselves.