Ethanol & Throttle - Toyota Nation Forum : Toyota Car and Truck Forums
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#1 Old 03-11-2010, 03:32 PM
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Ethanol & Throttle

When ethanol evaporates, it leaves a residue of varnish and other deposits. Does the engine design of the Camry call for ethanol to pass through the throttle body? If so could the ethanol be increasing the stickiness of the throttle?
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#2 Old 03-11-2010, 05:37 PM
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no the fuel does not flow through the throttle body. Your car has fuel injectors, one for each cylinder. Carbon can build up on the butterfly of the throttle body and cause it to be sticky. Do a little reading on how modern engines work.
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#3 Old 03-11-2010, 07:48 PM
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Before I got my 2007 Camry, I owned two cars. One was a 1972 Ford Mustang and the other was a 1988 Ford Taurus. I freely admit that I am behind on how modern automobiles work. I know about fuel injection and that most of the fuel goes initially through the injectors. I have been reading up. The design recirculates some of the unburned combustion gases to improve the gas milage but exactly where these gases reenter the system wasn't clear.
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#4 Old 03-11-2010, 08:03 PM
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Quote:
Originally Posted by sixtyone View Post
When ethanol evaporates, it leaves a residue of varnish and other deposits. Does the engine design of the Camry call for ethanol to pass through the throttle body? If so could the ethanol be increasing the stickiness of the throttle?
While ethanol may decompose (or polymerize) to form varnish, and may even be a solvent for varnish-producing substances, it doesn't, by itself, leave a varnish deposit. There are many other components in gasoline that are far more contributing to deposits - and additives to control them to a manageable levels. Quick 'gumming up' of the throttle is likely a symptom of fuel with insufficient detergent additive package.

As to your second post - yes, every modern car employs EGR (in one way or another) to control NOx emissions The exhaust gases are metered via the EGR valve and go into the intake manifold, well downstream of the throttle body.
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#5 Old 03-12-2010, 07:06 AM
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Egr
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#6 Old 03-13-2010, 05:29 PM
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How does the throttle body get dirty then? If the egr gases enter well downstream there should be nothing but clean filtered air before that, I don't get it,
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#7 Old 03-13-2010, 05:40 PM
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Originally Posted by warpedrotor View Post
How does the throttle body get dirty then? If the egr gases enter well downstream there should be nothing but clean filtered air before that, I don't get it,
A number of mechanisms contribute:
  1. Engine shut-down leaves the entire intake full of volatile hydrocarbons (OK, maybe not full, but certainly containing a bunch) coupled with considerable heat. This causes breakdown of the same, and deposits to the 'cool' surfaces.
  2. Do realize that air isn't just flowing one way in the intake; it's bouncing back and forth; the reason intake runners are a specific length (or can be varied in effective length) is to take advantage of that. This means that while the engine is running, the flow inside the intake manifold is back-and-forth, including all the way against the throttle. This means that the manifold (and the back surface of the throttle body) is exposed to the same hydrocarbon soup.
  3. Also realize that the air filter is not 100% - particles of small size get through. Coupled with sticky coating of the hydrocarbon soup, they can build up.
Counteracting all of the above are coatings of the intake parts, and fuel detergent additives. They do a decent, but imperfect job. The intake track cleaning takes care of the (relatively small) part the fuel additives miss. It also explains why different folks have different degree of trouble with deposits - some fuels aren't as effective at controlling deposits as others, and some drive cycles (short start/stop ) also contribute.
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#8 Old 03-13-2010, 06:03 PM
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Thanks for the info.
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#9 Old 03-14-2010, 11:03 AM
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On the V6 the EGR valve connects to the intake manifold right next to the throttle body.
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#10 Old 03-14-2010, 05:37 PM
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So I guess there's no PCV with associated gases to contributing to this mix? Used to be a source of crud at the base of the carburetors on old V-8s I used to work on.
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#11 Old 03-14-2010, 06:38 PM
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Quote:
Originally Posted by warpedrotor View Post
So I guess there's no PCV with associated gases to contributing to this mix? Used to be a source of crud at the base of the carburetors on old V-8s I used to work on.
Yes, there is PCV - but the amount of blow-by is much less in a healthy modern motor than it was 'back in the day' with the old stink-pots.

And frankly, one of the biggest advantages is having the old carbs go away - they had lousy cold-start mixture control, as well as cylinder-to-cylinder mixture variation that contributed to crud going into the crankcase. I remember the old cast-in-manifold Ford 6's having to run 2 or 3 different plugs to work around the too-rich and too-lean cylinders... Sometimes the best thing about the old days is that they're gone.
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#12 Old 03-14-2010, 09:15 PM
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Agreed, my Camry has about the same usable (needed) power as my last old v-8 had with an engine half the size using 45% less fuel without flooding or hesitating or stalling. I'm not too nostalgic either..
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#13 Old 03-14-2010, 10:06 PM
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Ethanol use

Quote:
Originally Posted by sixtyone View Post
When ethanol evaporates, it leaves a residue of varnish and other deposits. Does the engine design of the Camry call for ethanol to pass through the throttle body? If so could the ethanol be increasing the stickiness of the throttle?
I have a 2004 Camry and use E-10 Sinclair 89octane in a V-6.
I don't know what ethanol blend you are using [probably E-10 which is 10% ethanol and 90% gasoline] but it doesn't matter. Only air passes through the throttle body. The fuel is injected by each injector at each intake valve where it mixes with the incoming air. If you use a good air filter and change it every year,you shouldn't get any kind of deposits at all in the throttle body. Ethanol is almost 100% pure grain alcohol. They make about a 100 million gallons of it a year six blocks from where I live. Grain alcohol, like rubbing alcohol , evaporates without leaving any residue at all. Try adding Chevron Techron to a full tank of gas every 3000 miles or so to keep the injectors clean.A sticking throttle is a whole new subject.
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#14 Old 03-15-2010, 06:53 AM
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There is one. on the V6 it's located on the passenger side of the engine compartment.
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#15 Old 03-15-2010, 07:16 AM
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Quote:
Originally Posted by hossmaster View Post
no the fuel does not flow through the throttle body. Your car has fuel injectors, one for each cylinder. Carbon can build up on the butterfly of the throttle body and cause it to be sticky. Do a little reading on how modern engines work.
+1 this answers it all. An keep a clean filter for the MAF sensor good.

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