Misfire,

[Sean d]

Driving the Z to work this morning and after about 12 miles the car dropped onto 5 pots and wouldn't clear so I pulled up and turned the engine off, started it again and it was fine for a couple of miles and then got the odd miss under load, whipped it to a mates garage and he run a diag, Code 243 Miss fire cylinder 6 popped up,
On the way home tonight I have done about 30 miles of spirited driving with no miss whatsoever, whats you opinions guys, I have purchased a coil that I am going to fit tomorrow, the plugs have only done about 1500 miles but are Bosche 4 spark.

 

[mrscalex]

Don't rule out pin corrosion on the DME. That was my issue.

 

[Sean d]

Just a thought, which is 6 back or front

 

[mrscalex]

1 front. 6 back.

 

[Sean d]

Don't rule out pin corrosion on the DME. That was my issue.

OK, whats the DME and where is it located,

 

[mrscalex]

OK, whats the DME and where is it located,

The central computer. It decides in this case when to send current to the coils. One of my pins was corroded so it never sent the signal.

It's in the black plastic box in the back left of the engine bay as you look in from the front.

Once the lid is off look for the silver box with 5 or 6 connectors coming off it back left. The front and back connectors are regular push fit and the middle ones you push a small tab in and the arm moves back. Disconnect all before trying to pull box out.

And disconnect your battery before you start!

It may sound complicated but it's not.

You're looking for green or white fur on the pins.

It's a really sensible check to make regardless of issues. I am fairly certain this fault is what killed the old engine by fueling the cylinder with no spark, raising the compression and exploding the con rod/bearing. That's the condition I bought the car in so I can't be sure.

You should do a coil and plug swap first with another cylinder and see if the fault moves. If it does it's the coil or plug.

Other common causes are the MAF and vacuum leaks.

It's usually one of these 4 things. I think the DME is a rarer issue. If it's not any of these let me know and I have a full blown procedure to go through the more tricky checks one by one.