Has any Mk3 Golf owner seen this before please ?
P reg (96) Mk3 Golf 2ltr GTI, 8 valve.
Vehicle fails at random intervals, no spark from coil. Coil lead held to block, spark may or may not return when engine turned over. Plugs, leads, cap and coil replaced. Local VW dealer and local independent unable to diagnose despite having all the fancy gear.
Owner has found that if he unplugs and replaces the plug to the ECU, vehicle will restart immediately. ECU is Siemens 5WP4-256 ( 037-906-125R )
Does this ECU have some form of immobilizer circuit that may be mall functioning and is it safe to do a substitution test with an identical ECU from a near identical vehicle ?
Any input much appreciated, thank you, Pete.
petel@clara.co.uk
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Adam and I have had a couple like this. There is a problem with amplifier/coil assemblies and the Hall-effect triggers in the distributor can be suspect, however, the unplugging the ecu bit tends to throw doubt on these components unless it is coincidental. If the car has an immobiliser then the replacement ecu will have to be coded to the car, not a problem if properly tooled up. Really need to see the car while it is misbehaving to progress further.
Andrew
Simplicate and add lightness!
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Thanks for your reply Andrew. As I am not familiar with VWs, could you please clarify what this amplifier/coil assy is ?
Personally, I feel that the ECU is a red herring as well and I am now told that the unit does have an immobilizer circuit, so a substitution test is not viable without a laptop, lead and some fancy software.
Thanks again, Pete.
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The amp and coil are mounted together on the bulkhead. They are available separately but we favour changing as a pair if proven faulty.
Andrew
Simplicate and add lightness!
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Thanks Andrew. Will pass this on to the owner and advise of the outcome. Rgds, Pete.
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Had a similar problem with a renault megane. The RAC chap said it was probably the coil assemblies and that he had seen several similar problems on VWs. In the end changing all 4 coils did the trick.
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