salimshah

Your understanding is correct about the fuel re-entering the intake. But is it the fuel that you pumped in? If you had used the non Top Tier fuel, would it be any different. All I can say is that you will get oil fumes + air + evaporated-un-burnt-fuel. The percentage of the fuel you pumped in, in the vapors is going to be very small.

In my opinion what you see in the TB is a distant reason to use top-tier gasoline. Actual fuel path and combustion are the prime reasons.

Salim

N4TECguy

EGR principles work exactly the opposite of what you describe. Instead of recirculating unburned fuel (which would increase combustion temps), it recirculates exhaust gas. If all your emissions equipment is working properly, your spent exhaust gas should be mostly inert. When recirculated, it should lead to a dilution of the incoming combustible air, serving to lower internal combustion temperatures and thereby reduce NOx generation (which increases at higher combustion temps and contributes greatly to the visible "smog" you see in many cities).

The carbon buildup you see on a throttle plate is from the PCV valve. The PCV valve ventilates the crankcase, in case the high combustion pressures slip by the piston rings. If the crankcase is not properly ventilated, you see issues with leaks from seals (particularly the rear main seal, if the PCV valve sticks shut), and excessive oil consumption (if the PCV sticks open). Even when the PCV valve operates normally, you will pull some crankcase oil vapors through into the intake, where it will drop out and deposit on colder surfaces like the throttle plate.

Does the soot from EGR contribute to carbon buildup? Yes, but it is dry soot. It should easily wipe off, just like on your exhaust pipe. Furthermore, these engines are not direct injection and should not have a lot of soot generation. The problem truly comes from the "wet" oil vapors from the PCV, which serves to capture the soot and turn it into hard buildup as it heat cycles.

11bravo

Well, I am certainly glad I have a better understanding of that. Thank you for your thorough and patient explanation. I was apparently confused as to the travel path of EGR vs. PVC. For the record, that is not the reason I use TT fuels, though I did believe it might help keep the throttle body cleaner. I will no longer misinform the internet users of the world.

ColAngus

I love and support your giant explanation, but there is unburned fuel in exhaust, period. I believe (willing to be proven wrong) that the exhaust for EGR is taken upstream of the catalytic converters, plus laboratory combustion isn't even perfect and it's a long way from that in a consumer vehicle so there should be "a fair bit" of unburned fuel.
Now, does that mean all the #VTechronTierTopPowerPlus gimmick nonsense works? I doubt it. But... If there's some Magic Sauce in the fuel, it could certainly still be present in that area.

N4TECguy

If there were significant amounts of unburned fuel in the exhaust, the premise of EGR (to cool combustion temps by providing inert gas as filler material) wouldn't work. Like you said nothing is perfect, but there is definitely not enough fuel in EGR to be cleaning throttle bodies and intake manifolds...that has to hold true for EGR to work.

MellonC00

so....... should I clean the TB or not periodically? Also what should I do with my PCV value? Should I replace that once in a while also?

salimshah

I dont have the service manual, but I would extensively check the vacuum hoses at 120K miles and replace the PCV at that time. By this time valve cover gaskets would need replacement too [good old Toyota/Lexus]. Replace vacuum hoses at 240k.

I expect idling issues around 70-90k and would do the TB cleaning when I clean IACV, not before.

Salim