Petrol Types
Supermarket Prosecco or Corner Shop Champagne?
Over the course of a couple of weeks in early spring, my engine’s idle started to be kind of erratic, and it started to stall when reversing out of the driveway and at the junction at the end of the street. This junction, being on a slight incline, I just used to coast up to in neutral; but for some new and unknown reason, the engine wouldn’t always recover from the drop in revs when they dipped below the ECU’s ‘set’ low-end value.
All kinds of worse-case scenarios flashed through my mind…
Then, shielding myself from the spiral-decline-of-despair when researching potential causes, I started to think about the more simple and more logical candidate reasons for this new condition; and before long, at the top of my list was the new E10 ethanol-enriched fuel as the prime cause.
Comment: Apparently, it’s quite common for us owners’ to think the worst and quickly descend into a state of despair for the slightest reason.
Background: I imported my turn-key, MSD Atomic, EFI-topped Ford 302 engine from the US, and it was set up for 95 and running sweet-as-a-nut, but unknown to me 95 in the US is 97-99 over here in the UK.
So releasing that 95 is not 95, and when talking to some other owners, the majority of whom were using super-juice anyway, I was persuaded that I needed to remove the obvious variable from the equation… Or, as they said to me in no uncertain terms… “You need to stay away from that supermarket rubbish.”
Note: My engine was obviously running on the raggy edge of ‘good’ with the old UK 95 stuff, so, retrospectively thinking, it was probably a good thing for me that E10 was introduced.
Now… having been unceremoniously enlightened by a couple of seasoned drivers, I was directed to three options: Esso Synergy Supreme: Shell V-Power: and BP Ultimate.
Moreover, when despairingly reading my EFI manual trying to understand how the ECU took care of business, I realised I needed to better understand a thing called “Idle Air Control” (IAC). This was one area I was aware of and this was one area I was avoiding like the plague as it was in my ‘you-know-what-you-don’t-know’ grey-cell repository.
I reluctantly continued reading and getting to grips with this IAC rocket-science tech-talk, and it appeared I might need to tweak the square-bore throttle blades for them to be at a more optimum base setting for the new fuel type. The manual states “Tweaking might be required depending on conditions and engine type”.
I really was not a happy camper at this point…
I deduced the IAC takes care of business using the throttle blades base position as its reference point i.e. the amount it is physically set to be open at idle to provide a constant for the IAC valve to adjust the air/fuel idle mix, as necessary, and in real-time.
So, back to the plot, and having filled up with super-juice, the engine gargled and cleared its throats by swishing and swirling the good stuff around with gusto… The EFI controller re-learned and the engine gave a sigh of relief and settled down into a constant and very nice-sounding burbly idle condition. But then, the revs were a tad high and the IAC count was zero (which, according to the manual, might not be a bad thing in the grand scheme of things).
So, armed with all this newfound knowledge, I decided to have a fiddle with the throttle blades in an effort to lower the intake’s static percentage of air to allow the IAC to perform just as efficiently at a lower rev setting.
Note: The Lambda sensor monitors the air/fuel mix [downstream] and the ECU adjusts for an optimum stoichiometric (new word for me) air/fuel ratio for idle, cruising, and wide open throttle (WOT), so I didn’t have to worry about that side of the equation.
The procedure [according to the ECU manual] is to adjust the blade screws ⅛ of a turn at a time [at idle and when the engine is warm] until the IAC setting is between 5-12%, and at the same time fiddle with the ECU idle limiter to obtain a good idle value… A massive chicken-&-egg situation for me and it took a while, but now, the engine is happy so I’m happy.
As a consequence, I also don’t have to worry about fuel pipe corrosion or clogged-up jets or unnecessary tappet wear or knocking, as all those additional super-juice additives and detergents are doing what they do best… And I now get better mpg.
p.s. My lawnmower runs much better on the good stuff too (but it doesn’t cut the grass any quicker).
Cheers… Steve Hughes (Northern Region)