Misfire following plugs and leads swap

[MackemPete]

Just went to pick my car up after my mates garage fitted new plugs and leads. Car idles fine but had a misfire as soon as you tried to rev it.

He's going to double check the connections tomorrow, however I would have thought a misfire would be felt at idle too? I seem to remember that when I bought the car it spluttered a bit like this and it turned out to be coil packs.

[Supateg]

It's very easy to fit the plug leads but not fully seat them on the spark plug.
Double check I guess

[MackemPete]

It's the perfect idle that has me flummoxed. He's completely going to check the basics as it went in driving OK and came out misfiring.

[gruffalo]

What leads did he fit?

[LincsCerb]

Check that they have fitted NGK plugs. I recently serviced mine and euro car parts didn't have any NGK plugs but did have some Bosch super 4 which were an alternative part, so fitted them and had exactly the same problem misfire unload. So I replaced them with NGK an the misfire was cured bit annoying really as the idle was smoother with Bosch.

[Tanguero]

Good idle and misfire under load is typical of a coil pack failure or possibly an HT lead not properly plugged in.

[Boosted LS1]

gruffalo said:

What leads did he fit?

Good lord, not that old chestnut. I'd hate to think they were magnificent chores lol.

[MackemPete]

No following good advice on here I went with standard OEM from TVR car parts for the leads.

Plugs were DENSO Iridium Tough Spark Plug [VK20].

I've got my fingers crossed it's just a loose lead. Need her back for a run up to hartside on Sunday.

[Mr Cerbera]

I know I'm not a nice person but I would want 'my mate's garage' to explain why they didn't replace the plugs with the Manufacturer's recommendation ?

[Boosted LS1]

^
Maybe because have improved since 'back then'?

[Jhonno]

Boosted LS1 said:

^
Maybe because have improved since 'back then'?

Yep.

That is what I am running and it purrs with them, and new OEM leads and new Bosch coil packs.

[Mr Cerbera]

Boosted LS1 said:

^
Maybe because have improved since 'back then'?

Point taken

[gruffalo]

Mr Cerbera said:

Boosted LS1 said:

^
Maybe because have improved since 'back then'?

Point taken

There have been some quite recent cases of them causing a problem.

I would also not expect a supposed supirior product to have to improve so as not to cause an issue.

[MackemPete]

Cars all sorted. They had a couple of leads the wrong way around!

Definitely pulls a lot cleaner with the new plugs and leads. Smoother part throttle running with less surging. Makes it nicer to drive.

[gruffalo]

Good news!

Did you get up to Hartside?

[MackemPete]

Sure did. Woke a few people up too:
video

[gruffalo]

That looks epic, great stretch of road!