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[tgm147]

Right guys, making progress!

Fitted a new MAF yesterday and the car went like dirty stuff off a shovel. Once, the engine decided to hunt around at idle but that stopped. However this was the start of a new problem. Done about 50 miles in it today and all was fine until I was only a few hundred yards from home. The gearbox went into limp home mode. I pulled over, ignition off and on again and we were all sorted. 20 feet later, back in limp home mode but with the EML on. Limped it back to the house and plugged the diagnostics in. The voltage to the MAF sensor was only showing 0.2 with no flow detected over the sensor. I took it off, cleaned the contacts as much as I could with WD-40 and put it back together. It then registered a higher voltage and air flow over the sensor. This raised with the engine revs. Happy I'd sorted the problem, I took it for a spin round the block. 2 roads away, it gave up again and wouldn't drive on petrol or gas until I'd unplugged the sensor. It was a good tight firm connection so I can only guess that something is going open circuit or close to it?

When I unplugged the sensor completely it showed as nothing on the voltage on the diagnostics. Is tomorrow the day where I start taking the wiring loom to bits in the engine bay looking for a knackered wire?

[symes]

personally I would use electrical contact cleaner on connections not WD-40

[tgm147]

Was all I had. Going to have another fiddle with it this morning and if that doesn't solve anything I'll start taking the loom to bits unless anyone else has any other ideas!

[PhilRich]

When you say 'New MAF', are you saying Brand New OEM MAF ?

[tgm147]

When you say 'New MAF', are you saying Brand New OEM MAF ?

Yup, brand new one from Vauxhall.

[Cliffo B]

Anyone near with a known good running MAF?
I would be checking that MAF before I started pulling looms apart
In my experience they rarely fail unless suffered bad abuse
I always make sure of the connectors though

[Jimbob]

New Maf, does not guarantee working maf.

what are the readings with the old one...may pinpoint to wiring or maf then.

[Cliffo B]

Hope you did'nt spray WD40 into the sensor
The elements within don't like contamination of any sort

[tgm147]

New Maf, does not guarantee working maf.

what are the readings with the old one...may pinpoint to wiring or maf then.

0.4 volts at idle and no flow over the sensor. And no, I didn't spray WD-40 onto the sensor itself, just a little on the electrical connection.

[Kevin Wood]

I think you have two options:

Buzz all the connections through from MAF back to ECU with an ohmmeter. Give the loom a good waggle and check they are solid connections.

Borrow another known good MAF and see if you have bought a dud one.

The fact that it's losing both air temperature and MAF makes me think it's either the power supply or ground to the sensor that's come adrift.

[Kevin Wood]

Oh, and make sure all the engine loom ground connections are OK. I think there's one by the fuel rail on the 4 pot and another by the ECU?

[tgm147]

Right I've unwrapped the loom as far back as I dare and checked all the connections I can. The wires going into the sensor seem ok, there's no breaks till half way across the cable tray which is as far as I've stripped and I've given the connection to the ECU a good jiggle about with no change. The code for the air temperature has gone now too at random. Where is this sensor? I'll follow the wires back from that too. I can't find the earth points though. I'm still rather new to the electrics side.

[Kevin Wood]

Air temperature sensor is built into the MAF.

[tgm147]

Air temperature sensor is built into the MAF.

Well, that was easy! 

Just been out and bought a multimeter. Car is driving with the MAF plugged in but feels really down on power. 

right I'm guessing I need to measure the continuity of the connections back to the ECU which would mean common ground going to an earth and the other connection going to each pin on the MAF connection?

[tgm147]

Update time.

The fault appears to be in the plug itself at the MAF end. I've plugged it into the spare MAF and by moving it around, I can get it to make a good connection but as soon as the clip is pushed home, it's gone again. Like the cable has worked lose. Is it possible to take the plug on the MAF end of the loom apart? I've had a poke around but can't work out how it comes to pieces.