Intermittent misfire

[BlackMagic]

When I was on the motorway last night the engine started having occasional 'coughs'. The car was cruising at constant speed and the coughs were occasional (2 or 3 every minute or so). It then went away for a hour but returned later.

It sounds like a poor electical connection, but where to start looking? Does theECM hold a log of faults?

Any thoughts would be great before I start fishing around under the bonnet.

She is a 1991 S2.

Many thanks

William

 

[Dan944t]

Hi William,
i woukd sugest looking at your spark plugs , leads , rotor arm , rotor cap for any sighns of corrosion or cracks in the leads, and replace if needed or clean connections ect. make Sure all leads are pushed home correctly and spark plugs are tight also ect

daniel

 

[PSH]

Check your crank sensor multiplugs...could be loose, broken due to brittle plastic or just corroded....if these are fine check Dan's list..it's probably a loose/corroded connection somewhere..

Pete

 

[BlackMagic]

Check to see whether the rev counter drops to 0 when it "coughs". The signal to the rev counter comes from the DME, so this can be relevant. Any work done on electrics recently? Does the car have an immobiliser? Sorry not a solution, just stuff to think about / check. I had a similar issue that eventually turned out to be a loose plug under the fuseboard, but that's highly unlikely unless it's been worked on as mine had.
HTH