Carbon build up

What low compression ratio?

 

Build up carbon where?
From what?

Monitor your fuel efficiency.
Check your oil consumption rate.

If both remain constant, then you have no issues with 'carbon build-up.'
Good Luck!

 

Most toyota engines have compression near 10:1.

 

What gasoline do you guys fill-up with? TopTierGas.com brands would have adequate additives to control junk build-up.

Also I assume you are aware some Gen3's had a tendency for knocking typically when a homeowner made a tiny trip (like from driveway to street for parking etc) and then turned the car off, this tended to cause knocking upon cool-off and re-start.

 

Is it possible they all fill up at the same company source? Possibly as fuel quality issue?

 

Use a product like Seafoam or B-12 Chemtool to clean the fuel system and combustion chambers. Simple maintenance if you are concerned about carbon build up.

 

Consider a compression check and / or boroscope analysis from a trained mechanic? Not sure how easy/hard it is to do a compression check on a Prius (a little help , more experienced Priuschatters?), but a boroscope analysis can be done with the engine off and thus should be feasible .
How many Prii in the fleet?
Is brake wear a problem at 50k?

 

Bear in mind to get the spark plugs out (for compression check or whatever) requires taking off the wipers, the wiper motors, and a fair bit of trim around the bottom the windshield.

 

I think the Prius is just a noisy car. The engine noise on start up and at lie speed is normal.

 

The answer to the question I think is "Maybe".

But I also think the majority of Prius see a wide range of operational speeds, including freeway and highway speeds.

Even before I owned a Prius, I've always thought it good to have a vehicle get X amount of time at higher speeds. If for any reason I went a couple of weeks at all urban low speed driving, I would actually plan a trip on the freeway.

I also occasionally run a bottle of Techron through the fuel system.

A fleet of Prius, that never see anything but parking lot speeds? Is a pretty rare consistent and continual driving scenario. I'd think any vehicle used in that manner would be prone to carbon build up.

 

My wife, with one of our sons as an accomplice, pretty much forces me to drive up a local ski hill at least once a year. I'm guessing that would blow out the carbon.

 

Yes , yes, floor the sucker to "blow the gunk out" as Bill Cosby once said in his "200 mph" skit! Where to do this? "Oh any side street." Of course, the one gentleman who deprogrammed the Prius's 112mph speed limiter chip and got it up to 125 mph, IIRC, also went airborne off the road, crashed, and rolled the car at the end.
Maybe adding some Techron once in a while would be a safer option?
Still kind of wish I could borrow a boroscope and take a look inside those engines.

 

B-12 Chemtool does the trick with regular driving.

 

My person experience is that my Prius did gum up with carbon. So much so that I needed a new EGR value just short of 80,000 miles. It wasn't able to be cleaned as it was almost solid.

I did use cheap petrol though and now use Shell.

 

Interesting, thanks for the data point.

I wonder if the throttle plate and MAF are decent surrogate markers for a carbon rich exhaust, or if you can point to any reason your car would tend to run a fuel rich mixture.

 

60k miles of very short trips, often broken up with 30-50 minute gaps? Cabs in the UK have to either return to the rank OR park up waiting for the next dispatch via the computer. Obviously with the Prius the engine is off but it would fire up again when it cooled down and/or when floored. A UK taxi environment isn't good for any car. My diesels would get choked up too.

6

 

May I ask what were the critical symptoms of the carbon accumulating?
Did you also see any sooty-looking deposits on your spark plugs? Any change in compression ratio, higher amounts of pinging, or carbon accumulation on valves, piston , or combustion chamber?
I appreciate the info as I think many of us will experience what happened to you, only at higher mileage because our pattern of use is more a mix of urban and highway driving.
Replacing EGR valve has been easy on my previous cars at least, but disassembling to scrape off carbon is a LOT of work.