Hi folks,

A couple of weeks ago, after a long motorway run, I found my car to be losing power when accelerating – making a "put-put" sound as it did so. Easing off stopped it, but obviously that doesn't help when you're trying to pick up some speed. On the worst occasions the engine management light blinked lots.

Between a friend and a nice AA man, we diagnosed the problem to misfiring in cylinder 1. And while the AA man suspected the coil, following my friend's suggestion of gapping down the spark plug mostly fixed the problem, making the misfiring only happen when I deliberately put a high load on the engine at low revs.

Once back home I took the car to Arnold Clark (who had serviced it a month previously) for them to take a look...

They said they could see the logged problems with cylinder one, but couldn't find anything wrong with the spark plug or coil. They said this sort of problem is typically a fault in the ECU, and it would cost £400-£500 to replace it. They also said they found one of the cables was a bit loose, so they fixed that and told me to see how it went.

Of course, that made no difference.

I am reluctant to spend £400 on a replacement ECU when I am skeptical it will fix the problem. I figure they just told me that to make me go away.

Any body have any thoughts on this?

when did you last replace the plugs? and what "gap" did your mate set the plug at?

could be and sounds very much like its breaking down under load which could be a cracked plug (you probably wont be able to see it) or a damaged lead but as you have said it could also be the coil pack and or ECU start with the cheap things if its out of warranty

I don't think the spark plugs have ever been replaced – the car has done just shy of 30,000 miles. It was the AA man who gapped down the plug by tapping it once on the engine block.

He looked both surprised and annoyed that this mostly fixed the problem – he was sure it was the coil and there was nothing he could do to help.

I hope to take it to be looked at by a mechanic friend next week.

Plugs on the 8V should be replaced every 18k miles

Andy Monty said:

Plugs on the 8V should be replaced every 18k miles

Click to expand...

Ah well, it's possible that they were in a previous service. They are FIAT original plugs, and the AA guy said they didn't look too old, and should last 40,000 miles.

Maybe it's simply that they need replaced.

An update, and a question...

I got new spark plugs, but an investigation by a mechanic friend shows that the coil pack is not producing as great a spark for cylinder 1 as the other 3, so we reckon it's needing replaced. However the new spark plugs (gapped down a bit) is currently keeping the engine running fairly well.

I'm going to see if I can get hold of a new coil pack today. Are there likely to be any issues with the engine management unit with the new coil pack? (Or is there anything else I really need to know at this point?)