Occasional odd engine misfire

[phade]

Hi everyone,

I have a rather odd problem with my beetle. It has a very occasional misfire (eg. once every few days or so for a few seconds), but however I cannot find the exact cause of the fault.

When I used my VAG 1552 fault code reader to check the fault memory, it has always replied "No Fault Regonised".

I have done the following so far:-

- Replaced HT (ignition) leads. One of the old HT leads has snapped off due to corrosion
- Replaced relay 30 (ECU relay)
- Replaced relay 80 (fuel pump relay)
- Replaced fuel pump (later found out that the old fuel pump was ok)
- Checked the voltage from the ECU (J169) to the hall sender (G40). This was within specified limits according to my Digifant Fuel Injection VW booklet.
- Replaced distributor. The hall sender on the old one was faulty (I used a pair of pliers and wiggled it's socket). The ECU did not log this fault.

I have thought of a couple of other possible causes, but I cannot tell if it will fix it or not. They are the following:-

- Ignition transformer
- Engine oil temperature sender. I had found that the socket was very loose on the sender its self.

If replacing the above doesn't work, does anyone have an idea of what else it could be?

Cheers,

Phil