1.4 Petrol won't start - Immobilser problem?

I have a very strange problem with my 1.4SE. Most of the time it runs perfectly, starts first time, all good. Then, for no apparent reason, it simply won't start. The engine turns over very strongly, but won't fire at all. Not so much as a splutter. And there is no smell of petrol. It did this once when it was in the local garage for a routine service, and the limited diagnostics the mechanic was able to do showed that the injectors were shut off. He was convinced that it was an immobiliser problem.
The problem comes and goes at random, starting fine for a few weeks, then failing again. Sometimes it won't start again for about a week, then suddenly fires up first time and runs perfectly. And so it goes on. . .
The trouble with this is that the car simply can't be relied upon to get you anywhere (or back again), as you just don't know when it's going to fail. And once it does it's impossible to restart.

Any suggestions as to what this might be caused by, and anything I can do to sort it, would be very gratefully received.
 
When the car refuses to start have you noticed if the immobiliser symbol on the dash is present, or in other words not cancelled (disappeared) after a few seconds as it should after turning the key at startup? If it is present try using another key if you have one. Anyway even if the immobiliser startup validation check fails the car should still start for a moment before dying I understand.

Andy
 
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Thanks very much to everyone for the replies.
So am I right in thinking that if it was the immobiliser that was responsible the engine would always run very briefly before cutting out?
It never does that, just turns over quite happily but never fires up or runs at all. Then (usually days later) it will start first time, no problem at all. There is usually no warning light displayed, although sometimes the engine management one comes on.
I've seen suggestions that faulty crank or cam sensors, or possibly the earth connection behind the front headlight can cause this kind of thing.
It's just very difficult to know where to start looking.
 
Hi Andy,

No, there is no flashing 'car with key' symbol, and it never starts even for a moment. So it's looking like it isn't the immobiliser. The only thing that comes up when the diagnostic computer is plugged in is a code apparently relating to the injectors being switched off/not working (the diagnostics at my local garage are fairly limited, and not Audi specific). But what's causing this, if it's not the immobiliser, is a bit of a mystery.

Cheers,

Steve
 
Just to be clear. When the ignition key is turned to its first position you should see a yellow car symbol, (assuming same as my 1.6) which then extinguishes after about 3 seconds. If you see nothing further the immobiliser has checked out okay.

My great sympathy with your problem, intermittant faults are a devil and it it is rendering your car unusable - I would not want to dirive it anywhere knowing I might not get back.

I can only suggest you get a proper full VCDS scan.

You may want to consider inviting Tom(Timmus) for a professional visit if he thinks it might be beneficial - you are not that far from him in Lancaster. Likewise for Paul(Depronman) in St. Anne's.

Hope you get it resolved.

Andy
 
I certainly think an Audi specific scan is the best place to start
I know the 1.4 ECU will kill the injectors if it detects a mis fire, it does this to protect the CAT, so it has that inherent capability

I would hope a VAG COM scan would yield the problem
I'm likely to be busy tomorrow, but can fit you in on Sunday if you want to bring it over to St Annes, should it refuse to start I can easily take you back to Clitheroe

Cheers,
Paul
 
Hi Paul,

That sounds great. I think a scan definitely seems like the way to go. My only problem is that the car is currently in its non-starting mode. It went to the garage in Cltheroe this week for a minor bit of work on the fan belt tensioner, the work was completed without a problem - and you can probably guess the next bit. . . As soon as the mechanic tried to drive it out of the garage, it wouldn't start. And it has remained in that mode for the last few days. So it's stuck there until Monday. I'm just hoping that after another weekend's rest it will randomly decide to start again, which is what it usually does.

So if I can get it to run, I'll bring it over sometime next week if that's OK, whenever suits you.

Cheers,

Steve
 
Hi Paul,

That sounds great. I think a scan definitely seems like the way to go. My only problem is that the car is currently in its non-starting mode. It went to the garage in Cltheroe this week for a minor bit of work on the fan belt tensioner, the work was completed without a problem - and you can probably guess the next bit. . . As soon as the mechanic tried to drive it out of the garage, it wouldn't start. And it has remained in that mode for the last few days. So it's stuck there until Monday. I'm just hoping that after another weekend's rest it will randomly decide to start again, which is what it usually does.

So if I can get it to run, I'll bring it over sometime next week if that's OK, whenever suits you.

Cheers,

Steve
OK in the week any time after 7pm
 
Just to be clear. When the ignition key is turned to its first position you should see a yellow car symbol, (assuming same as my 1.6) which then extinguishes after about 3 seconds. If you see nothing further the immobiliser has checked out okay.

My great sympathy with your problem, intermittant faults are a devil and it it is rendering your car unusable - I would not want to dirive it anywhere knowing I might not get back.

I can only suggest you get a proper full VCDS scan.

You may want to consider inviting Tom(Timmus) for a professional visit if he thinks it might be beneficial - you are not that far from him in Lancaster. Likewise for Paul(Depronman) in St. Anne's.

Hope you get it resolved.

Andy

Thanks Andy. I'm going to try and get it to Paul sometime next week - just as soon as I can get it to start.

You're absolutely right about intermittent faults, they can drive you mad. I had a lovely 205 GTI for many years, until it developed similar undiagnosable problems. It became so unrelaible I finally gave up on it and sold it, something I've always regretted. But I learned my lesson, and there's no way I'm giving up on the A2. We've had the car from new (2001), done 200,000+, and it's had the occasional problem, but on the whole it's been fantastic, and this is the first time it has become consistently unreliable.

Cheers,

Steve
 
Much delayed Update: the A2 is finally back on the road again, after spending the entire lockdown immobile in the local garage. After endless attempts to discover the source of the non-starting problem, we managed to track it down to the relay under the passenger footwell that controls the fuel pump. Worked out this might be the source of the trouble as when the car was not starting there was no sound of the fuel pump priming itself when the ignition was turned on. Once the relay was replaced the car started first time, and has continued to, so that seems to be problem solved. Really nice to finally have the car back up and running - had almost got to the point of thinking it might never happen. Anyhow, just thought this info might be useful for anyone else experiencing a similar problem - it's certainly something to eliminate, as it is fairly easy to check. And the lack of the usual fuel pump priming noise from behind the dash is a very handy clue as to what might be causing the problem.

Cheers,

Steve
 
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