Really simple cure to dodgy running.

[ZippyVR6 0]

Hi all.

 

For a few months I have been plagued with dodgy running, nothing serious. Just fast idle on start up and hunting for revs till warm, and the occasional stutter when coming off the gas.

 

I have changed, and cleaned ISV, cleaned up MAF. checked leads and plugs, and all sorts.

 

Not once did it occur to me that a higher octane fuel was the answer.

 

Last year when the fuel prices went mental I stopped using 98RON fuel.

 

I kind of forgot it even existed, and only last week when I picked up the wrong pump by mistake did it occur to me I always used to use super unleaded.

 

This week the car is a different beast. It starts right, revs settle down immediately, and doesn’t jump about like it used to.

 

In hindsight it seems blindingly obvious, but thought it might be of use to someone.

[Conker 0]

Good result!

 

Here's a question... Would you bother driving for 10 miles to get 98 or 99 RON (V-Power), or drive for 1 mile and get 97 RON (Esso Super). Is the extra miles worth it, or is 97 RON enough?

[muppetlab 0]

Hmmmm. I have been using high octane petrol (vmax, tesco super) for the last week or so in an effort to make my car run a bit better for the Mot. It does seem a bit less lumpy through the rev range. However it does seem to have trouble starting in the mornings now, needs a bit of pedal where as before on low octane it used to fire right up. Might be a coincidence, cant say for sure until i check it out with some low octane stuff.

[Critical_Mass 10]

I have to go out of my way to the the vpower stuff - even more so when i move house. But i definately think its worth it, the car just feels smoother and slightly more eagar on the throttle.

 

Though its at 116.x pence at the moment, and who knows if/when it will go up further :(

[WigsVR6 0]

I always use high octane fuel (Tesco's 99 Ron) and never have any idle problems. However I spent a week in Wales last year and couldn't get hold of any super unleaded so ended up buying the nomal stuff. The change in the engine was instant with it stalling at junctions, roundabouts ect most of the time in fact getting out of the garage forecourt it stalled on me.

 

Makes me wonder if some of the stalling problems that are posted on here are caused by using 95 Ron fuel and not the ISV. Wondering what people think about this is it feasable?

[timthetinyhorse 0]

am i correct in thinking that the ECU adjusts to different fuel types and therefore when moving back to 95 the ECU may take time to notice the difference and thus cause the stalling problem? this may just be modern cars so if this is the case ignore what i just said.

I tend to run my 9A on a mixture of both fuels depending on how my pocket is feeling that month but i cant say i see a huge difference ither than around an extra 2mpg.......is this just a VR thing?

[Veearrhsix 0]

Though SORN'd for a while now, I do recall noticing drastic change in engine 'mood'. Re: various fuel types.

[Mawrick 0]

I would presume the ECU might be doing something - as in the "manual" of the cars it normaly states that it will performe x horsepower with a given RON.

 

And basicly 98 RON is of better quality then 95 :)

[Bullfinch 0]

If you look in the owners manual a VR6 is meant to run on 98 RON unleaded. Stick to that and all should be fine. 8)

[Supercharged 2]

Yep - it's always meant to be 98RON

[8vMatt 1]

Right then, as it does seem to make a difference, best stick to the good stuff then. Shouldn't matter about the cost, considering the small mileage I do :norty:

[Jonny777 0]

I'll only ever buy petrol from Shell and BP now and only they're vpower/ultimate ones.

 

Car gets far better MPG and runs a hell of a lot better on it. I won't touch supermarket fuel as i've heard stories about it being full of crap.

[KipVR 1]

I would presume the ECU might be doing something - as in the "manual" of the cars it normaly states that it will performe x horsepower with a given RON.

 

And basicly 98 RON is of better quality then 95 :)

 

spot on, RON is a measurement of a fuels ability to withstand pre-ignition, the higher the number the better. All the ECU does is use the knock sensor to sence where the limit of the fuel is, therefore advancing (or rather not retarding) the ignition further with the 98 RON, which in return gives you better performance. It usually takes the ECU a while to adjust it's settings though, and of course it's only as accurate as your knock sensor so make sure that's working.

[millerman 0]

i normally put shell v power in its closest and i have a v power card and get money off fuel vouchers :D but sometimes i use std unleaded and i cant say ive ever noticed that much of a difference it certainly does not cut out at roundabouts or run lumpy and i dont think i get less miles to the gallon but then i drive with a heavy right foot so i dont get too many miles to the gallon.

i find some of your findings very bizzar i could understand if you had the 1.8 16v with out the knock sensor as you would notice the difference like ryan_16v has found but not the vr ???

[OllieVR6 0]

I won't touch supermarket fuel as i've heard stories about it being full of crap.

 

You should have a read of this, I only use Tesco 99 these days:

 

http://www.thorneymotorsport.co.uk/tuni ... port.shtml

[timthetinyhorse 0]

a very good article it has to be said but i feel that the advantages may not be as aplicable to much older cars due to the different engine management types etc.......very informative though, would be interesting to see a similar test complete on a older car with more primative management

[Jonny777 0]

I can see the advantage of the 99 RON stuff but thats fairly obvious as its higher, but i dont have any that sell it near me to even try it.

 

Rather use the specially produced fuels from the specialists. Summat from Tesco doesnt strike me as being the best...

[Philuk 0]

nearest shell with Vpower to me is 6/10 miles away, nearest tesco with a decent fuel is 40 miles away. i use sainsburys super which is 97RON lol

[muppetlab 0]

A friend that races stock hatch told me the tesco's stuff is among the best he could find, apparently lots of them use it in racing so it cant be that bad,