[V6-12v] Timing belt tools

James4ihl at aol.com James4ihl at aol.com
Mon Feb 23 18:55:20 EST 2004

> On a totally different subject - here's one for you to scratch your heads 
> over. On my hesitation problem, which those of you who are regulars will 
> recognise, I had a bizarre experience today.
I always fill my car with super-unleaded 98 ron fuel, because that car is 
supposed to run on the higher octane fuel, according to the manual, fuel cap and 
ignition manual. You can fill it with 95 occasionally and it won't bother, but 
you shouldn't use full throttle/ high speeds for extended periods, you know 
the deal.

Well, here's the thing - the hesitation disappears with the 95 fuel, and 
idling and everything are better. Now, that really shouldn't be, at all. But it's 
a clue, right?

So, here's the thing. I know that the timing map on this generation of engine 
has two map knock ranges, for 98 and '95 or less'. And the timing map retards 
the timing when it detects 95 or less fuel. So my initial thought is what if 
it's 'stuck' (for want of a better term!) on the 95 setting, so that when I'm 
putting 98 in, as I normally do, it's not, in effect 'advancing' the timing 

Does that make sense? I know what I mean, but it's hard to describe it on 
email... Anyway, so the question that follows is: I know that the ECU 
retards/advances the timing in response to the octane rating of the fuel, but how does it 
work out which fuel is in there? In other words, which sensor, or combination 
of sensors does it use to work out that info? Because my problem probably 
lies there...

Any thoughts?

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