1.6 16v dodgy starting-immob issue?

[prawn]

Guys, I'm trying to do a bit of fault finding for a friend at work, the car in question is a 51 plate 1.6 16v leon.

The issue is that it's having massive trouble starting regularly, when you turn the key, it'll start instantly, but run for about half a second before cutting out again. sometimes a bit of throttle helps it, but usually it just continues to die. sometimes it takes 4-5 turns of the key to start, others it won't go on the key at all, and required a bump to start, where it's still fairly unhappy, but fires and runs after being forced to turn over for a good 10-15 yards.

We have now also found that if you keep the key held when it starts and dies so it just keeps cranking, after a few fires and a load of throttle it'll eventually take and it's off.

I ran a VAGCOM scan on it (v409-1) and it won't scan module 1 for the engine and says ''can't sync baud rate''

I did an auto scan, and the instruments module came up with an intermittent coolant temp sensor, which I've replaced. it seems a little better, but i think that's just coincidence.

the only odd thing to come up in the scan, was the immobiliser, which instead of just saying ''no fault found'', instead said ''No fault found. OR DTCs not supported by controller OR A communication error occured''

Would this imply a possible issue? the way it's cutting out is very similar to an A4 i had with an immob problem.

Also (possibly related) every time the car is turned off, the mileage on the trip resets, obviously not the overall car mileage, but the trip mileage. i thought this was very odd!

If anyone has any suggestions as to what could be causing the problem, i'd love to hear them!

Cheers

Nick

 

[robbob]

One way of fixing it she should of brought my car!

Ok it might have a pool but least it starts and runs and its a fast swimming pool

 

[Alexis27]

Throttle sensor?

 

[prawn]

Would the throttle sensor be likely to cause this issue? Once it's started it runs and drives just fine.....

Also, what are the likely causes of VAGCOM not being able to connect to the engine control module?

 

[Alexis27]

Does it run ok from a standing start once it's warmed up? Dodgy throttle sensor can mean it's fine when it's warmed up, but you still might see stalling if you try to set off from a red light.

Some info about baud rates here: http://www.seatcupra.net/forums/showthread.php?t=153789

Are you able to give it a try in another VAG car?

 

[Fl@pper]

immobiliser chips going out of sync is a known issue and also the reader coil (fit's over the ignition barrel) is a part that is a known fault on older vehicles and to be honest they are the same design as good as

may be worth a look/test ??

 

[prawn]

Cheers for the help guys!

alexis27: that's awesome about the Baud rate issue, I'd not seen that before. I'll get that changed and give it a scan at lunchtime to see if it works. Hopefully it'll show up some codes that might indicate what the problem is.

the car does seem to always start fine again once it's warmed up, it's only initial starting in the morning, or after it's been parked up at work all day that it causes problems.

Fl@pper: if the immob had gone out of sync, would it still start after some time, or simply not at all?

What's involved cost wise in replacing either the throttle sensor or the immob chip/coil reader?

 

[Fl@pper]

the start eventually thing is what made me think of the reader coil part and not sure on leon cost but last couple i bought for polo + golf were £35 odd for parts

strip out column cowling and trace wiring back to a connector, unclip and fit new one

not hard to do in all honesty but they usually leave an implausible signal fault when they play up so may be worth just keeping an eye on until it gets worse, sounds daft but easier to diagnose and cure than a sporadic fault sadly