1.2 puretech turbo misfire under load

[sjhaycroft]

Hi all. I've been experiencing an odd issue with my Citroen C4 Cactus 110bhp. When driving down the motorway in 5th gear and foot to floor at around 60-70mp/h the car will occasionally misfire and then continue to accelerate. It doesn't do it all the time and only does it in 5th and at those speeds when I'm guessing the engine is working it's hardest? I took it to Citroen who suggested spark plugs as these were black on the ends. I had the spark plugs changed and still the problem remained. I had been exclusively filling up with Costco 99 fuel for the past 8 months. I was going away for the weekend and needed to fill up. With no Costco around I filled up with Shell V power. I wondered if the fuel could be causing the issue so tried replicating the issue down the motorway on the way back but for the life of me I couldn't get the car to misfire. Could fuel actually cause a misfire?

Thanks for any input.

[sjhaycroft]

Also, there were no error codes logged on ECU.

[sjhaycroft]

It misfires with the costco 99ron fuel

[sjhaycroft]

Any ideas as to what causes it? If it was something like the fuel pump would it misfire more often and not just when it's at motorway speed? With regards to shell fuel, I don't mind paying the 10p extra per litre as I'm only having to fill up once a month. Very economical little motor.

[sjhaycroft]

Does anybody know what makes shell v power different to costco 99 aside from the mix of detergents? I read somewhere that with turbo petrol engines the MON number of fuel is more important than RON but don't know how true that is.

[sjhaycroft]

Twig62, how long your 208 been doing it for?

Anyone any ideas as to the cause of the misfire?

[sjhaycroft]

I've run in two tanks of shell v power now and the car misfired again last night.

[sjhaycroft]

It only happens when my foot is to the floor.

[sjhaycroft]

and only does it in 5th gear however last night is did it when foot was to the floor in 3rd gear. Prior to last night it's only ever done it in 5th on the motorway and when foot is right down on the accelerator.

[sjhaycroft]

So are we saying it's normal for the engine to do this?

[sjhaycroft]

Twig62, did you ask about the issue at your second service?

Regarding reducing the spark plug gap that mignon mentioned. I was on a parts website looking at spark plugs and it said 2 bosch plugs were compatible with this car, the only difference was that the spark position was 5mm on one and 4mm on the other. What would using one of these over the other do to the engine?

[sjhaycroft]

[sjhaycroft]

[sjhaycroft]

I'm guessing it's the spark plug gap?

This is from NGK website

[sjhaycroft]

Sorry, my mistake. When I had a look at the plugs that were taken out of my car when it was serviced I thought 4/5mm would be big. What would the difference in those 2 types of spark plug on the engine performance (if any)?

[sjhaycroft]

Mines a 5 speed manual. Is's twig who's got the 6 speed auto.

[sjhaycroft]

When I started running mine on v power it didn't do it for a tank or 2 and then the problem came back. I'm now giving esso synergy 97 a whirl.

[sjhaycroft]

Hi. Sorry to resurrect and old thread.
I've just had my gearbox replaced under warranty. Apparently some form of factory defect (so they said). I told them about this misfire and they are adamant that the problem was coming from the gearbox.
Can a gearbox issue actually give off the same sensation as a misfire? (That shake/judder).