Topic: Gasoline Additives

[tenpenny]

Here's an interesting question for anyone out there with a ChemEng degree.

I have a 98 Subaru Legacy.  260,000 odd kms.

Here in NB, all of the gasoline comes from the same refinery; the additives are put into the gas at the loading rack when the transports are loaded.  Each brand has their own additives, all slightly different chemistries.

I usually run a particular brand of fuel, but once in a while, depending on where I am, I'll switch brands.  After one such switch, the "check engine" light came on in the Subaru.  (did the gas cap thing, all the works.  Stayed on for a few days).  Took it to the dealer, but on the way to the dealer the light turned itself off, and there were no codes stored.  However, about a month later, I switched brands of gas for one tank.  The light came on the next day.  I switched back to the other brand, and after 3 days, the light went off.

About a month later, due to location, I used that other brand again.  The light came on the next day.  After a week and two tanks of my regular brand, it went out again.

What in the additives would be causing this?  I'm assuming the O2 sensor, or one of the other sensors, is not happy with the chemical mix.

Anyone else out there notice this sort of phenomenon?

[weebl]

That is a weird phenomenon!  I've experienced phantom CEL's before, but they were always one-offs and I could never pinpoint those to a cause.

I'd definitely be interested in hearing if fuel additives could cause this.  Fuel out here is similar, I believe we have 3 supplying refineries, and of course each brand's additives are mixed at the rack.

[tpl]

If there were no codes stored then it was not a misfire  

I think that the only sensors that could go on would be the O2, knock sensor or fuel system.

If the CEL was steady then  the system would wait for some number of engine start cycles and if it did not re-occur then turn itself off.

Exservice wherefore art thou?

[exserviceguy]

Hi Ho Gang,
It would be ever so helpful to know what code was behind the CEL.  I've only known of 2 cases where a CEL didn't produce a 'pending' or 'hard' or 'historic' code.  First is when the fault self corrects and the computer memory, (which is limited), self clears before someone has a chance to scan the system.  The second is my current driver that has flashed the CEL 3 times in 9 months, but never locks a code.
If this were truly fuel additive related, (God knows an almost 8 year old vehicle with over a quarter million klicks operating in the ever so friendly environment of NB wouldn't have any other troubles under the hood), my bet would be on the knock sensor.  If a less than well refined blend of unleaded with the young bouquet of low octane were added to a getting tired engine with an aged to perfection ignition system it is highly possible to get a preignition knock that the timing control can't overcome, thus a knock sensor code.  The knock sensor will easily reset if the knock ceases over the course of one or two start and run cycles.  I know that it's hard to ask a car owner to jog over to a repair shop to hunt down a CEL code, when a lot of these shops charge dearly for the task, (hey they're just trying to make a living too).  So final opinion is: If the light comes and goes irregularly and sparsely, and no other running faults are noted, leave well enough alone and keep gassing up at Uncle Irvine, (big brother loves your money).  Maybe you could luck in and find someone with a genaeric code reader.  If you can get a crash course in using one, (they're pretty easy) run it for the weekend and you might come up with the code.

[tenpenny]

Actually, it was Uncle Irvine's gas that caused the CEL to come on....Esso, for some reason doesn't.  Now the fuel thing could be a total coincidence, I don't know.  Never rule out coincidence.  It could be weather related; I didn't pay attention to the weather involved those days, perhaps the CEL was scared by the sun (such an unusual occurence this spring).

The weirdest thing was that the morning I was on my way to the dealer, a 10 min drive, the CEL turned itself off about 1/2 the way there....I assumed it would reset afer some restart cycles, but I didn't know it would reset while running, in motion....and then clear its memory.(!)

And you're right, I can't conceive of any other possible problem after all those miles!!!

[barrie1]

Have you had alot of rain in your area lately as the moisture can cause weird things to happen with an engine as well. I have seen codes tripped for a short time until it self clears itself out by moisture trapped in the wrong spot.  

[Wetson]

Fussy engine.  Kind of reminds me of the story about the princess and the pea.  I have used Esso brand in my car since I got it (Dec 04) and Just put PC in and no problems.  Car feels the same.  

I wonder if it's something else that coincedently happens whenever you change brand of fuels....

[safristi]

There is an article on some of the engineering used in the fuel system that may explain the Problemo on Mr Kerr's article this week on Canadian Driver...read on MacBeth.........\..
Ya gotta eat/read yer HOME cookin' fellas.......