Yet Another Rough-Running Prius - Check Engine Light Lit

The drama continues. Having no confidence in the local dealership, my housemate talked with the owner of a local independent shop I had located. They were amenable to doing a cautious series of tests to limit the amount we had to spend. He was still thinking "head gasket" though, and a possible $3200 repair cost. (!!!) When we went to pick up the car today, to bring it home first so I could test for exhaust in the coolant, the Hybrid System warning light came on - and stayed on - when it was started at the dealership. No sign of coolant in the exhaust by sight or by smell, but this - which we had never seen before with this car. A little chat with the Service Manager and the "tech" we had spoken with over the phone revealed that they had gone ahead and done some of the expensive testing before asking her for authorization. So they wanted us to leave with the car, no charge, but with the warning still on. We were told that there was "no problem" driving it with the 'take the car to a dealer NOW' warning on. We left it there anyway, and both sides will be consulting with Toyota tomorrow. What we found out from the now-free testing was that cylinder one has a chronic misfire not changed by swapping plugs or coils. A leakdown test revealed "50% loss on intake side". They thus wanted to look at the valve springs. Is valve spring breakage a know issue...? Is the car really safe to drive with that warning on? Are Priuses really not all that great after all...?

 

The car has never been run hard, and the timing belt has never broken. Only a defective valve spring could cause the above scenario...

 

"what was the cautious testing to be comprised of?"


Basically, everything short of major part replacement, one at a time. The dealership did a leakdown test that we got for free; next I'm going to use a double-chambered test kit to test for exhaust gases residue in the coolant. The dealership also swapped plugs and coils between the #1 cylinder and another one, and the misfire stayed with the #1 cylinder. It looks like it is likely either a leaking head gasket (but a tiny leak only) or a bad valve spring or valve. Still, there is one internet video in which very similar symptoms were caused by a plugged EGR system. How often does that happen with no EGR code being thrown...?

 

The car didn't see a lot of short trips in which the engine didn't get hot. Some, I'm sure, but not a lot. She is remarkably tough in that she doesn't use the heat in local trips, to avoid an ICE start. The oil was never sludgy or black when changed, and it was always full synthetic.

As for driving it as-is: we're considering it, at least for a few months. Since more than half of her trips don't require the ICE, the car can still be used much of the time with no misfiring.

 

I would have sworn they said that there was an EGR code. Well, that is the next course of action - IF there is no exhaust in the coolant. Thanks.

 

I bought a test kit that lets you check for exhaust in the coolant. When I bought it I assumed that it tests the coolant, but it doesn't: it tests the air in the small dead space at the top of the radiator. You suck in air through the fill cap on the radiator, and test that. So naturally the photos I'm now looking at of PIP radiators have no bloody fill pipe and cap on the radiator! Can I do the test using the air inside the coolant reservoir, after running the engine up to operating temp and driving it a bit...?

 

EPISODE IV: The Creeping Menace

As I mentioned, I bought a double-chambered CO2 test kit. The plan was to drive the car yesterday evening, take it for a slightly longish spin with plenty of brisk (for a Prius) acceleration, pick up a gallon of gas for the snowblower, and then do a test of the air in the coolant reservoir. The engine started ok, no white smoke or smell of antifreeze, but it ran just a little roughly. It was raining, though, and when she turned the wipers on, one was moving more slowly than the other, and they tangled a bit. I later found, after a much shorter trip than planned, that the nut on the driver's side wiper arm hadn't been tightened nearly enough at the dealership. Now we know that they probably did do a leak-down test, but we don't know that it was done competently.

The first test came back completely negative, so I checked the fluid by doing the "breath test" suggested in the instructions. Instead of turning yellow after 3-5 exhalations were tested, it stayed blue until about 15 puffs, then finally turned obviously yellow at 25. There is what looks like a date, in European format, stamped on the bottle, and it looks like the test fluid expired quite a few months ago. I repeated the test of the reservoir, this time doing 60 puffs, and the fluid stayed completely blue. For what that's worth...