Intermittent Ignition failure

[Strev]

1990 mkii 8v GTi - C. 180,000 miles.

Any ideas - ignition keeps cutting out mostly for fractions of time but sometimes for 3 or 4 seconds. Its not an earthing problem (have checked earthing points), as the stereo keeps working normally when it happens. Its as if I've turned the ignition key off and on again. It will do this several times on my short 10 minute drive to work. I think it gets worse the longer the journey, but this might be coincidence.

Any suggestions?

Cheers.

 

[mk2mark]

That's weird, I just had a similar problem this morning. The electrics cut out twice as I was going round right hand bends in low revs when I accellerated. The second time it cut out for a good few seconds and I turned the key off and on which seemed to fix it. Seems like a very strange problem. I need to check the rest of my grounds.

[rubjonny]

start by replacing the ignition switch, then look at any alarm or immobilisor that may be installed
The TCI unit is worth replacing as its easy to get to and they are plentiful in scrappies as all MK2s with electronic ign had them. You'll find it on top of the ecu bracket under the small plastic cover at the left side of the scuttle area

[Strev]

Mine is usually for such a short period the rev counter drops to zero then back again and warning lights flash. The other morning though i nearly came to a standstill before it came back again. Very odd.

[Strev]

When you say ignition switch, do you mean where the ignition key is? Also, what is the TCI unit?

Cheers.

[rubjonny]

the ignition switch is bolted behind where the key is yes, you can just about get the screw out with a bent watchmakers screwdriver
The TCI unit is part of the ignition system, it controls the coil

[Strev]

Thanks - which would you say is most likely to be the problem and is there any way of testing without replacing?

Also - any idea how I immobilise my immobiliser? Its one of the touch key types, located in the blancing plate above the lights switch.

Cheers.

[rubjonny]

I'd say most likly is ign switch, then imobilisor followed by TCI or ign fault elsewhere.  Might just be a damaged wire, or possibly your hall sender starting to break down.  This is the plug in the side of the dizzy, though usually when they go the rev counter goes dappy.

Since its an intermittant fault testing is very hard!

[Strev]

Rubjonny - Last night's trip home was worse then ever - cut out 4 times trying to park at home! Definately seems to be worse the longer the journey/ warmer the car. Does this make it any easier to diagnose?

Cheers.

[rubjonny]

not really, but it points more to an engine bay problem.  If you wiggle the ign key does the engine cut out?
Also run the car at night and see if you can spot any arcing around the leads, dizzy & coil