Yet Another Rough-Running Prius - Check Engine Light Lit

2013 PIP Base. This is my housemate's car. She drives it gently, and I drive it when needed - also gently. It first seemed a bit rough in the 42-47MPH range earlier this year. We assumed that it was old gas, ran it down to one fuel bar, and refilled it with fresh mid-grade or premium - I forget which. It made no difference. She just had the car in for the 30K service last month, and had them clean the fuel injectors as well, at my suggestion. Again, no difference. With the arrival of the current frigid weather, it also began, according to her, to "Ice Lock" - that banging sound on cold startup as ice chunks in the motor break apart. I advised her to always let the engine warm up fully on a trip before shutting it off. She uses EV mode only for local errands, but also uses Hybrid mode once or twice a week for longer trips. Today she started it to run an important errand, and got a rough, noisy startup (I don't know if it was ice lock or just ran roughly) AND the check engine light came on and stayed on. It remains on, and the car is definitely running rough for about 20 seconds on ICE startup. She says that last week she may or may not have found some non-viscous liquid with an oily sheen, under it. (She had to move the car for snow plowing and doesn't know if the liquid came from this car or from somewhere else.) This car has never run at all rough before this year, and had only ice locked a couple of times since new. It gets serviced one a year (we don't drive a lot of miles since retiring) and is always parked outdoors. Ideas? It got new Toyo Celsius tires last year.

 

Thanks for the detailed reply. I also saw, somewhere, that a loose air box to MAF fitting could let enough air in to mess up the air/fuel ratio. Thoughts? I'll take a look at both as best I can, but I don't do much work on cars at all, these days - too many health issues.

 

I already have a BAFX OBDII reader that I use with my Leaf. What app is best for the PIP, and where is the OBDII port on it?

 

Looks like that app is Torque Pro, and I've installed it on my phone.

 

"This is not a thing, there's no ice inside - if there was then trying to start it would ruin the engine "


I was exaggerating a bit, but it is indeed a "thing." It sounds like what I described, believe me. Here is a thread on it.

Cold start with vicious knocking. | PriusChat

IIRC, Toyota eventually issued some sort of service bulletin on it.


I've actually been here for many years, having joined somewhere around 2010. For some reason the site forgot I existed and I had to create a new account.

 

It doesn't sit "unused." It gets used about twice a week in EV mode, and taken for longer trips (20-30 miles) with the ICE running once or twice a week - just about every week. It has always run great up until this year. It gets serviced every year.

 

We try to use the fuel in the tank up every month or two. The first thing we did, as I wrote, was to make sure it got a full tank of fresh gas, with Techron in it, and it made zero difference.

I will be checking the gas cap when I read the codes tonight. I think that's unlikely, though, as the rough running came many months before the Check Engine light.

One theme I'm seeing here is the use pattern being the culprit. As long as the ICE gets fully warmed up with every drive in which it runs, I don't see the problem. We rarely shut it off with the engine still running - we live at the bottom of a hill and it usually shuts off well before it gets home. She retired several years ago, so counting from then it went at least two years with this driving pattern and no problem. When I use the car every month or so, I don't baby the engine. I'm now leaning toward the dealership never having really cleaned the throttle body and EGR pipe...

Oh, BTW: where is the OBDII port located on the Prius? I want to read the codes tonight.

 

Thanks. I got the codes - three for misfiring cylinders - and cleared them. They didn't return immediately but one was "pending." IIRC, they are P0300, P0301, P0302. The car idles roughly, but smooths right out with throttle. The plan is to have the dealership clean (with more than car spray) the throttle body and the EGR plumbing, plus new plugs.

 

Hey, if getting three things serviced fixes it, I'll consider that a win! The throttle body and EGR should have been done at least once in six years, but the mileage is so low that no one ever thought of it. The snag I see, though, is the spark plugs. My god!!! That should win a bad design and/or 'best way to keep people from working on their cars' award. I've seen $1200 quoted for plugs and coils, so I hope the blasted coils are ok...

Speaking of working on my own cars: yes, I did, for many years, starting when I was about 15. I'm 61 now, and once I could afford to have others work on my cars, I went that route. I'm trying to think of the last real, hands-dirty automotive job I did myself... probably a tuneup on my then car, a '95 Civic EX, about 7 years ago, before I started driving Leafs. Yes, the PIP's oil is clean - so clean it's hard to read the stick. The car was serviced in the Fall, and as usual the oil was changed then.

Finally: do the codes for misfires have another, hidden meaning? The Torque app didn't mention any...

 

The quote was in a comment section on a decent YouTube channel. The video was on how to change the plugs - by removing every trace of the windshield wiper system, first...