Well, as you may have read I filled up with Tesco 99RON last night. All seemed OK until this afternoon when I reset the ECU and re-aligned the throttle body with VAG-COM.

I did this to speed up the learning process and let it adapt to the extra RON's. Now when I come to a stop in traffic it idles roughly, sometimes right down to 500 rpm :thumbdwn:

How did you reset the ECU? I know the Mondeo requires the engine to run at idle and fast idle for a few minutes before taking it for a drive to adapt itself....

Chris

Reset the ECU with the Ross method I will say I am hoping it will solve itself the more it runs.

This is the gist of what it says in the Haynes Manual for the VW Golf & Bora about the engine management system ECU:

The ECU adapts to changes in operating conditions and stores the optimum settings found. These 'learned' settings are lost if the battery is disconnected. When the engine is restarted it may idle and run roughly until the ECU has 'relearned' the best settings. To help in this process, take the car on a road test of at least 15 minutes, covering as many engine speeds and loads as possible, and concentrating on the 2000-4000 rpm rev range. On completion let the engine idle for at least 10 minutes. During this period turn the steering wheel occasionally and switch on high-current equipment such as HRW and heater fan.

Thanks Denis.

I've been out for a drive and it feels a little better.

Meanwhile here's a VAG-COM torque plot to give an indication of difference.

The "other" fuel was Shell non-Optimax

Sounds like the throttle body hasnt reset properly to me.

Sometimes they dont like being messed with.

These 'learned' settings are lost if the battery is disconnected. When the engine is restarted it may idle and run roughly until the ECU has 'relearned' the best settings.

a.k.a. Rediness Codes. They can be set manually if you know the right channels to go into and have VAG COM etc.

Put Tesco super unleaded in my vRS recently(97 Ron?), car lacks punch - feels like its on normal unleaded, I usually use BP, Morrisons, Shell superunleaded, anybody else got any comments on Tesco's super unleaded?:confused:

I usually use Tesco 97RON super or Shel non-Optimax - this test was with Tesco 99RON (not available everywhere). I agree that the car does feel a little different on the 99 but I've yet to decide if it is better/worse.

looking at the graph above from vag-com i'd say that initial torque is better (being higher) but the other fuel gives a higher spread across the lower rev range... the other fuel also appears to give a higher peak torque figure, although the 99ron fuel gives a flatter more constant curve...

i'd say you need to make sure the ECU is settled and run a few more tank fulls of this 99ron fuel through to see how it gets on.

i'm yet to find a Tesco's in the walsall area that has this fuel so will stick to Optimax / Ultimate for now.

forgot to mention that my vRS has a very rough idle atm and has shown the engine light on and off for a few weeks now... i booked it into the dealers for them to have a look and they have ordered a new TB for me, its booked in for the replacement on the 16th Jan.

I recently did a trial of optimax and found the idle to be all over the place, so went back to normal fuel, which was fine, then 2 weeks later the engine light came on and I needed a new intercooler pipe and a few other bits. Havent yet tried any 99 ron or optimax since, but I predict that it will idle just fine now.

Having used Tesco 99 Ron since it came out, I can only rave about the stuff, even tick over, pulls and pulls to the red line, and very good fuel consumption.

Perhaps I have been very lucky, as I have had none of the symptoms as mentioned by others.

Pleased to report that my car has now got used to 99 RON and is running very well. Idle is still hunting a little but it did that before - dirty MAF I suspect

I've been using different kinds of 'super unleaded', as I can't always get to the same filling station. I've not noticed any problems.