NWS4Guy

Correct, not sure how I missed replying to this earlier I apologize. Carbon builds up naturally anyway, it's the washing of the valve by fuel with additives which prevents the buildup (not stops, just prevents excessive amounts from forming) on the valves.

That said, the injector is doing the spraying, not getting sprayed. Think about a garden hose, or showerhead where there is hard water - you see desposits form around where the water comes out of the holes, over time it can cause the spray to divery and not focus correctly until the lime deposits are removed.

Rhytid

Your analogy of the garden hose or showerhead doesn't make sense to me. Yes, in WATER, you could have minerals dissolved in it. However, in the case of our cars, we are talking about carbon buildup coming from burning of OIL, no? And as far as I understand it, there is no OIL in the fuel, correct?

I don't mean to sound like I am beating a dead horse but just logically, this issue is driving me crazy.

IAS5

go to page 14 here...

http://www.google.com/patents?id=fLI...page&q&f=false

m444

IAS5, Thanks for the nice patent citing for an engine valve with a catalytic coating on the valve stem to help prevent deposits.


Rhytid, Gasoline is hydrocarbon based & one can get gummy varnish residues just from the gasoline. Gasoline is a complex mix of short and longer chain hydrocarbons, including special additives. The injector nozzle is pretty fine & can get clogged with fine particles and gummy buildup.

Oil deposits can build up on the intake valve stems from crankcase venting to the intake, exhaust gas recirculation and reversion of combustion chamber gases into the intake (due to cam timing overlap).

There is also oil blowby from the rings/pistons, which can plate out on the cooler surfaces, after combustion.

Rhytid

Hey, thanks for trying to explain this issue to me. I guess my confusion stems from the fact that I was under the impression that the carbon buildup of the valves was strictly due to the burning of oil residues. And that in non-direct injection engines, this problem was resolved by putting additives into the gasoline to "dissolve/prevent" the carbon deposits.

My old brain is having a hard time wrapping itself around carbon deposits forming from just gasoline itself. I can even understand "gumming" of the injectors but having a hard time with carbon deposits. If the carbon buildup of the injectors is all due to "blowby" then OK. That explains it.

IAS5

should have read a little deeper into the page- sorry!

NWS4Guy

In addition to blowby there is also the EGR which takes the unburned vapors and recirculates them - those parts which didn't burn will typically be heavier anyway and more likely to be gummy.

surgeon

Back to square one. The claim that there was 'bad gas' seems baseless. I have driven another 600k and it has recurred. This time with a full stall.

Rhytid

First of all, so sorry to hear that. That really sucks.

Just a wild conjecture here but is it possible you have a bad ring on one or more of the cylinders? I mean, if the injector is getting carbon buildup and the carbon is MOSTLY from oil residues, isn't this a likely scenario?

Or am I out in left field?

m444

Gasoline is a hydrocarbon compound. It has carbon in it.

"Gasoline is a complex mixture of over 500 hydrocarbons that may have between 5 to 12 carbons."

http://www.elmhurst.edu/~chm/vchembook/515gasolinefs.html

See those graphical representations, the "C" is carbon.