My ETS light has been coming on regularly and I understand that I'll need a new control unit in the near future. My question is this: Is there any connection between using high octane fuel (93 Octane) and the throttle body? The reason I ask this question is, it seems that when I use the higher octane fuel, the ETS light stays off and the car runs smoother than when I use regular gasoline. Is this just a conincidence or is there a connection?

i was just reading this and other responses,low octane gas in these particular cars causes carbon build up in the eng.ie;valves rings etc. your crankcase ventilation is responsible for getting rid of some of it.where does the crank case vent to?thats more theory than fact,however the ones ive had to replace on customers cars,for some reason most of the time have been people who run low grade gas or dont get reg service.good luck.

What can expect to pay an independent Volvo repairman to replace the ETS.

I've seen a couple posts here about a correlation between fuel and the electronic throttle body. Its something I'd like to see explained in more depth becase the throttle body is no where near the fuel. Fuel is injected into the intake manifold way downstream of the the throttle body.

The only thing that passes through the throttle body is air.

A good point, I guess the air has to be quite badly polluted to explain the contamination..? And why isnt the dirt trapped in the air filter then?

According to a Volvo mechanics here, cleaning solves many of the ETM cases (but obviously not all) so the contamination seems to be the main issue.
As far as I understand, the crankcase ventilation passes through the throttle body. Could it be crankcase fumes that are causing the problem? If so I guess both oil quality and oil change interval could be involved. The amount of crankcase fumes would probably increase considerably as the engine gets worn?

Or is it simply combustion fumes flowing backwards when the engine is stopped? I have seen "gumming" in the carburettor on some cars I have had. The gumming was above the fuel nozzles so I find it hard to believe it was caused by the fuel. I have always thought it was caused by combustions fumes when turning off but maybe crankcase fumes is a better guess?

Any thoughts?
Rgds
Erik

True, in theory. Take yours apart some time, and explain how all that black stuff came out of the air...
--
01 V70 2.4 M5 and a Mini

Air is full of crap and gunk, fuel would actually clean it a bit. I'd wager that there also a contribution of minor amounts of oil mist from the turbo bearings.

What kills the ETS module is heat and gunk that accumulates in the throttle body. So it's possible that running cheap regular gas would lead to more gunk accumulation, but I doubt it.

Remove your TB/ETS module and give it a good cleaning. Then run high octane quality gas and see what happens. You have nothing to loose and lots to gain.
--
'88 240, '92 745, '98 v70 John, Tampa Bay

I thought I saw an authoritive post in which someone did a failure analysis on a failed throttle body unit. He found that the failure was due to wearing away of the resistive material used in the potentiometer (a variable resistor), which electrically controls the throttle body. There is a "wiper" that moves across the potentiometer when you step on your accelerator pedal. Every time you step, it wipes across the surface of this resistive material. Over time, the material wears away, and voila - ETS failure.

If this is the case, then it has nothing to do with the stuff flowing through throttle body, since the potentiometer has no idea what kind of gas you are using. I suggest that your observation is just a coincidence, and the potentiometer material will shortly wear away so much that your throttle won't work at all.

Keep good walking shoes in the car.

http://www.brickboard.com/AWD/index.htm?id=884279