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.

[E-bmw]

Based on the principle that it is the fuel burning that causes the "fire" of course the fuel can be the root cause of the "misfire".

[stevieturbo]

So are you saying it is misfiring with the supermarket petrol, or Shell petrol ?

[sjhaycroft]

It misfires with the costco 99ron fuel

[Bennachie]

There are reports of something similar elsewhere; cured by exclusively using Shell fuels, but standard 95 ron not V power. The v power you have put in will clean the system but you are gaining nothing by using 99 in your engine....

[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.

[GreenV8S]

I suppose it's possible that the engine is a little marginal under those exact conditions and some small difference in the fuel composition is just enough to provoke a misfire. I've read about people attributing misfire issues to the introduction of ethanol blends and that's the sort of thing that can vary between fuel brands.

[Mr2Mike]

Bennachie said:

There are reports of something similar elsewhere; cured by exclusively using Shell fuels, but standard 95 ron not V power. The v power you have put in will clean the system but you are gaining nothing by using 99 in your engine....

Turbocharged engines running high compression ratios are exactly the kind of engines that tend to benefit from higher octane fuels.

[FredClogs]

We've just bought a cactus 1.2 110bhp and i had what I thought was a misfire the first time i drove it and googled to find its a fairly regular feature of this engine.

First thing i suspected was i hit the rev limiter or the traction control had kicked in as there is no rev counter on these things and the 3 pot engine is pretty willing but I'm not sure and it hasn't happened again.

I do think your wasting money putting 99ron fuel in it though i can't find any suggestion it needs it.

[GreenV8S]

Sometimes more expensive fuel grades have a lower ethanol content and give better mpg as a result of the higher calorific value.

[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.

[Twig62]

sjhaycroft said:

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.

Interesting as I have a Peugeot 208 fitted with this engine which occasionally does the same thing. I mostly run it on BP or Shell 95 octane but occasionally treat it to a tank full of V Power/Ultimate. I think it has done it when any of the fuels have been in the tank.

[Classy6]

Run it to near enough empty, then fill it back up again with £10 worth of the other fuel. If it start's running like crap again you'll have your answer.

[Kccv23highliftcam]

Mr2Mike said:

Bennachie said:

There are reports of something similar elsewhere; cured by exclusively using Shell fuels, but standard 95 ron not V power. The v power you have put in will clean the system but you are gaining nothing by using 99 in your engine....

Turbocharged engines running high compression ratios are exactly the kind of engines that tend to benefit from higher octane fuels.

now, now, now, there you go with that logic again...

[Bennachie]

The turbo is the size of a cotton reel - really, it is soft blown and does not benefit from anything more than 95.........

Good engine though...

[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.

[FredClogs]

Does it only happen if you bury the accelerator into the carpet in top gear at cruising revs?

[Mignon]

Same advice as I gave one another thread. Reduce the spark plug gap.