1.8L starting rattle, knock, events

Never. Owned since Sept. 2009, 19.000km.

 

That isn't "knock" or "pre-ignition". It's something in the valve train. I was thinking fouled plugs might be the cause of all this, but it sounds like something not adjusting in the valve train.

 

My two occurances happened under similar circumstances:

1. Backed Prius twenty-five feet out of garage in ECO mode. ICE did not start.
2. Washed Prius.
3. Drove Prius twenty-five feet back into garage in ECO mode. ICE started and ran for three to four seconds before I shut it down.
4. Next morning, started car in ECO mode. ICE knocked and vibrated for five to ten seconds and then ran normally.

The first occurance was in August 2009; second was in October 2010. Currrent mileage is approximately 20,800. Same event has happend in the above circumstances on other cars I have owned, i.e. '97 Buick LeSabre.

Conclusions/theories:

1. Although one can point to similar ocurrances, the frequency of the event is low, random, and probably not capable of being consistently duplicated by testing procedures for Toyota to recognize it as a problem. Pardon my pessimism.
2. There does not appear to be any damage to the ICE after this occurs which indicates that it is not a mechnical interferrence problem.
3. Concur with paprius4030 unburned gas theory as a possible cause, either in cylinders as a rich mixture, or causing carbon to dislodge from back of intake valves into cylinder(s), causing the engine to run rough and knock until excess fuel and/or carbon is burned off.
4. Bottom line for me: It would be nice to confirm what is actually occuring and I look forward to Prius Chat for further developments, but at this point it is not something I am worried about as far as the reliability or longevity of the engine/car.

I appreciate all the thought and effort of fellow Prius owners to solve this mystery. Keep up the good work.

 

Bob if it means anything the 4.0 V6 in my FJ will start rough if it is exposed to temps +40 F or colder. Most of them do that. No knocks, but the engine can become very "lopey" for up to 10 seconds

 

Listening to the video, it sure sounds like metal to metal contact, like the timing chain would make, if loose and rubbing. I believe this engine has an oil pressure powered chain tensioner? That would fit in with the symptoms, if the tensioner leaks down or some other problem, and then it starts working again with oil pressure.
This is the first I have heard where an 08 has this sound, maybe I haven't read enough threads. Never heard on my 07.

 

Voted Never/Not Yet-- 07/10 build, 3,500 miles, started in 40-100 degree temps.

 

19000 km over a year, I've never experimented this phenomena. However, since the beginning I've been using the 98 RON fuel...
Brgds

 

Carbon deposits make no sense, unburned fuel makes a lot of sense. It could be like starting a flooded engine. Some cylinders catch ignition some don't.
Alternatively, valve timing malfunction at start. I doubt if Bob's testing can uncover the issue.

 

Below is a link to an excellent article in Motor Magazine, that makes a lot of "sense", concerning carbon deposits.

The article explains how carbon deposits occur and performance problems they can cause, including the type of problem described in this thread. It is a good read for anyone with an open mind. My only critique of the article is that it is written for repair shop owners and emphasizes remedial decarbonization services sold by repair shops; however, it does not discuss regular use of complete fuel system cleaner additives as a preventive measure.

MOTOR Magazine Article | MOTOR Information Systems

 

The article is written to sell cleaning solutions. It omits a simple fact that engines decarbonize themself when taken out for a nice Hwy driving (Italian tuning).

If carbon is such a widespread problem, why only 2010 Prius is knocking and not other cars or even the previous generations?

 

Well just to set the record straight...my 08 did it once also. I agree there seems to be more complaints of this in regards to the Gen 3 compared to the Gen 2. But with these cars being so new I still think it has more to do with unburned gas left in a cylinder or 2 from the night before. That's my uneducated opinion, and I'm sticking to it LOL

 

[quote:Originally Posted by friendly_jacek
The article is written to sell cleaning solutions. It omits a simple fact that engines decarbonize themself when taken out for a nice Hwy driving (Italian tuning).
If carbon is such a widespread problem, why only 2010 Prius is knocking and not other cars or even the previous generations?

The below excerpts from the MOTOR Magazine article support paprius4030's opinion, and mine, that the problem may be fuel related; such as, a stuck open injector, which would flood the cylinder after the engine is shut-off, and again when the engine starts, until the injector unsticks and closes; or, a stuck closed injector, which would cause the other cylinders to be overfueled until the injector unsticks and opens; or, injector(s) with partial restriction and uneven fuel spray pattern; or, lots of other possiblilities.

Let's all be "friendly" and keep our minds open.

"most injector designs rarely fail due to mechanical or electrical faults. The most common problem relating to injectors is restriction. Even slight restrictions will skew both the injector’s atomization quality and the fuel volume it’s able to deliver at a given engine load and rpm.

Given time, contaminants in fuel tanks, fuel lines or the fuel rail—or even in the fuel itself—will always restrict injector flow; that’s a fact. Foreign particles such as rust will also accumulate within the injector filter or fuel filters to effectively reduce fuel flow. Extremely small rust particles may even pass through the tiny injector filter itself, causing altered spray patterns as well as reduced injector volume; they may even prevent the injector pintles from seating properly (see photo 1 on page 50).

Whether a pintle is sticking on or off its seat, overfueling of cylinders will always occur. If an injector’s pintle is off its seat, not only will the corresponding cylinder be flooded with fuel, but also the PCM (via O2 sensor feedback) will reduce fueling to other cylinders, causing a lack of performance (and a reduction in fuel economy), and creating the potential for engine, piston or ring damage. On the other hand, if a stuck pintle never opens, that cylinder will receive no fuel at all and the PCM will try to correct a lean bank issue by overfueling the rest of the cylinders on that O2 sensor bank. These scenarios are common on vehicles whose fuel systems have not been regularly maintained. Injectors need to be very clean for optimum system performance and fuel economy.

Injectors. Aside from the injector plugging issues from fuel contaminants mentioned earlier, carbon deposits (from heat soak) that build up on fuel injector tips will inevitably cause an uneven fuel pattern spray. As a conical spray pattern deteriorates to unevenly atomized type patterns, an increase in activated carbon buildup will also naturally occur."
​

 

The night before the knock happened, I got in and moved the Prius 2 feet ahead and shut it off. I think I shut it off while the ICE was "warming up".

The next morning the knock occurred. It never happened after that.

Could it be related to something in the ICE and moving only 2 feet ahead and shutting down immediately? I notice that sometimes, when I park my Prius and engage the parking brake...the Prius slightly moves forward (like some gears "lock"). Maybe that slight movement is enough to cause some issues when ICE starts up? Maybe shutting the ICE while warming up AND that slight movement is creating the issue?