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OT - Can an engine run better on 2 cylinders than 4?


LandyManLuke

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Firstly, an apology, this relates to my wife's Focus. I know it's off topic but I'm running out of ideas....

The sorry saga starts a couple of months ago, when the car completely died. It turned out the ECU had failed. A new ( actually second hand/reprogrammed) ECU was required, and appeared to get us back up and running. However, things have not been 100% since.

Along the way, the spark plugs, coil pack and crank sensor have been changed.

On Friday, I decided to pull the leads off in turn to see what was happening. no. 4 had no effect, where as pulling one of the other 3 slowed the engine and made it run even worse.

Given that the coil pack is wasted spark, I would have expected a spark issue to also effect no. 2, but removing the lead on number 2 caused the engine to falter - so it's doing something with the lead on.

Anyway, as a set of leads is relatively cheap, I have replaced the lead on no. 4, and the car now runs worse than it did before! It idles badly, is down on power (more so than on 2, which is also worse than it should be normally, of course) and subsequently has trouble reving.

I don't understand this, how can the engine run better on 2 cylinders than 4?

Is there a mechancial problem that could lead to these sorts of issues? the ignition side has been through about every change it can.

Luke

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Sound as though the coil pack has died.

What quality of coil pack did you fit, we have given up fitting intermotor ones, some don't even work out of the box!

We now only fit a new genuine ford coil pack which incidentaly is a very different design to the old ones.

Be sure that your useing the right spark plugs (i'd imagine ngk tr5a10) incorrect plugs will burn the coil pack out

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Thanks for the reply Dan,

It's a third party coil pack, fitted by a garage when the car first broke down when I was working away. Have you seen them fail like this? it appears to be creating a spark, I guess possibly at the wrong time?

A new set of Bosch HR78NX ('Super 4' spark plugs, fwiw :unsure: ) went in last week, and I've removed and cleaned the IAC. Changing the spark plugs didn't appear to make any difference, at the time.

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Cheers for the experience-based comments - I'm definitely lacking in experience on this one.

I think an original missfire is what killed the ECU in the first place. One of the chips on the ECU was toast. The suspect HT lead could have been the original cause of this, some 6 weeks ago.

It's the wife's car, I hardly travel in it, so it's difficult to say what the history of the missfire is, but there must be a cause to the original ECU failure.

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