Carbon build up

Rough running that got worse quickly. The car really struggled to run and was knocking and clattering. The new EGR really helped but I have since had to run some fuel system cleaner through and that has helped significantly.

But as I've mentioned in other threads, the driving here is different. My car barely got to 30 mph and mainly consisted of accelerating up to speed, coasting for a couple hundred yards before braking, turning onto another road and repeat. Then there were the quiet days explained above where the car would cool then only be driven half a mile and allowed to cool - and repeat for 10 hours. On a busy day it was foot to the floor playing catch up. A nice steady run for 20 miles at 60 mph every day would have been the dream journey.

 

Carbon build up mainly affects direct injection engines and since there's no fuel contacting the valves there no way of cleaning it but to scrub the valves by hand or do walnut shell blasting, but since we have multi port injected we can alleviate carbon clean up by using fuel injection cleaner and ones in a while give it a good 1 mile high rpm run once a week, and using good oil changing on time helps too.

 

I am not familiar with the symptoms that the OP described, but the spark plugs that I removed from my 2011 at 93k had the least amount of carbon that I had ever seen.

 

If carbon buildup is a problem try RXP. Ive heard many great things from people claiming it made a difference. It is a little orange bottle and typically costs $6 to $8. It is designed specifically for removing carbon build-up from the engine. Most autoparts places keep it behind the counter, just ask them and they will know what it is.

 

perhaps because it's such a different engine from camry?

 

Many vehicles are using Variable valve technology to add egr functions to the vehicle without the use of a egr valve. I am too surprised that there is an egr valve on these vehicles.

 

can you think of one with an engine like the prius?

 

It is the same block as in the corollas with a different head. It is an Atkinson cycle, after reading up on the motor I've found out that the egr works in conjunction with the VVT to further increase thermal efficiency. Most cars have been using VVTI to replace the egr (as well as increase engine performance.)

 

thanks! so prius is looking for efficiency/emissions and others are looking for performance?

 

Ya, the VVTI that the Prius has increases performance as well as efficiency.

 

One can only hope so, or else your combustion chamber is taking a horrible beating

 

Which of course has nothing to do with EGR valve.

Speaking of the combustion chamber though, is carbon build up in the chamber a problem in Prius ? Or any car for that matter ?

Addendum: I spent a little time Googling my question. The short answer seems to be that long life plugs with minimal carbon deposits is good evidence that all is well and 'cleaners' are best left on the shelf in the store. If carbon is being deposited, the fuel injectors seem to be the vulnerable target, and then a cleaner has at least a rationale for use.

 

Put a container of Chevron Techron in your gas tank about every 6 to 8 months and I don't think you will ever have any trouble. I have been doing that for years.

 

Question: Is it possible to use VVT to achieve EGR functions on an Atkinson cycle engine? If so, I would have thought Toyota would have done it, to save on the cost of including an EGR valve. I'm guessing it (i.e. VVT-EGR) is not compatible with the necessary late closing of the intake valve on the Prius Atkinson cycle engine, so an actual EGR valve had to be used.

Further, has the EGR valve, or clogging thereof, been confirmed as the cause of the severe knocking at startup experienced by many G3 owners?

 

I used to get the knocking at start up, well it happened about 3 times and I believe the modification was carried out as it stopped happening at about 30,000 miles. I'm wondering if the modification is what is causing the clogging of the EGR valve. Perhaps the original manifold was better but had this occasional knocking. The new part doesn't cause knocking but does cause a silent (and thus un-noticable) build up instead.

 

Don't forget that Prius has cooled EGR, how could you achive that with VVTi?

Why cooled EGR? To avoid knock maybe?

 

I believe the real reasons for having an old-fashioned EGR valve are simple. It's too hard to do using VVT in an Atkinson cycle engine. The Prius engine already uses VVT, to control the Intake valve timing as part of the Atkinson cycle control. I guess they haven't figured out a way for it to do both EGR and Atkinson cycle, all in one.

And maybe it's cooled (though this is not unique), to reduce the risk of igniting the fuel-air mixture flowing in and out of each cylinder.

At this point, I'd like to clear up what may be a common misconception about where the rejected (pushed back out) fuel-air mixture goes to. It doesn't just hang about in the intake manifold, or push back out towards the air cleaner. While one piston is beginning its (open-valved) compression stroke and pushing out mixture, another cylinder is just beginning its (normal) intake stroke. So, the air-fuel mixture being rejected by one cylinder is simultaneously being sucked into another. There's a kind of "hopping about" process occurring inside the intake manifold, where the last slug of mixture goes into one cylinder, "gets told Not Wanted here" so flows out and sideways along the manifold to the next cylinder on its intake stroke.

This probably explains why it's so common to see liquid fuel residue in the bottom of the IM. (This is probably mostly non-volatile fuel additives, rather than raw fuel - the fuel components will have evaporated away, leaving the anti-knock and other additives behind.) Anyway, as there's a lot of fuel-air mixture rushing in and out of ports and back and forth along the manifold, I guess it's not surprising that some additives condense out.