Corolla 1.8VVTI 1ZZFE Misfiring When Cold

[John Singleton]

Kia Ora from New Zealand.

I (my wife) have a Corolla with a 1.8 1ZZfe engine that I have recently changed the valve cover (rocker box) gasket on. That's the only thing I did!

Since then the car has had a persistent, harsh misfire when running from cold at low revs, under reasonably heavy load, for approximately the first 5 to 10 mins. After that it seems to run fine and pulls like a steam train. There are no indications on the dash.

I have changed the spark plugs and have even pulled the ECU fuse (to try and reset the ECU) in an attempt to clear the fault and this appears to have helped a bit.

All I can think of is that one of the coil-overs has an issue, but I've had one of them go before and this fault feels totally different.

Do you fine guys and gals have ANY ideas before I start spending $$$$'s on parts that I may not need?

[FROSTYBALLS]

Moved to the Corolla club.