Misfire due to oil in combustion chamber - causes, replace/repair engine?

What is most likely to cause this issue is the lack of engine oil changes at the proper interval (5K miles), using a poor quality of engine oil, or allowing the engine oil level to drop below the lower dimple on the oil dipstick.

It definitely would be much more expensive to repair the engine vs. buying a used engine for $400 and swapping the original engine out, labor would probably cost ~$1,500.

 

This dealer is probably incompetent. Bring it to another dealer.

If you know how to remove the spark plugs, take a look at them. At 3000 miles, there shouldn't be much wear on them. They would have to be severely fouled to cause a misfire code.

You probably just need to clean out the injectors and make sure they are working properly

 

JC91006 Is probably right first make sure that what dealer told you is true.

Only if you are thinking of replacing or tearing down engine:

If only problem of the engine is the oil getting past piston rings then first I would test if problem would go away by cleaning piston ring grooves and oil return holes. You can partially clean them by pouring solvent or diesel into cylinders from spark plug holes. And leaving it for day or two. This has worked on some Toyota engines that have used lots of oil. You have do oil change afterword since cleaner that gets through gets into your oil. Also you have to get rid of cleaner that is left in the cylinders. Normally easiest option is to crank engine without spark plugs but with prius you may need to do something a bit differentially.

If the engine has run with almost no oil then only real repair is to replace engine.

 

At 165k miles, many things could go wrong with the car engine. However the Prius engine does hold up quite well so unless it's been neglected, it shouldn't have severe problems that require replacement this early on.

Many people have burning oil issues at your mileage. Make sure your oil level is not low, that "might" be the reason for your problems but it's something you should keep an eye on. My cars burn up to 1 qt of oil in 1500 miles or less. So a car that only holds about 3.75 quarts, at 5500 miles, you'll be pretty near empty with your engine oil.

You can try dumping a bottle or 2 of Techron fuel injector cleaner into your fuel and see if things will improve after a couple tanks. This is probably what the dealer would call an "injector cleaning".

 

I would check to make sure the injectors are all working properly, this dealer should be able to do it with it taken partially apart. You really shouldn't drive a car with a misfire, it could do more damage. Does the check engine light flash or remain lit? They say it's safe to drive a car with a lit check engine but not safe to drive a car with a flashing check engine light

 

Your oil change intervals are OK. The implication behind your question above is that you do not periodically check the engine oil level. If this is true, then it is highly likely that your engine has been consuming some oil, the oil level dropped below the minimum acceptable, and engine damage was caused by insufficient lubrication.

At this point, you need to see what the spark plugs look like. If your car ran OK for 3K miles after the plugs were changed, then I doubt that fuel injectors are the issue.

 

A low engine oil level is the most likely reason for the engine damage that your car has, assuming that the dealer tech's description of the problem as posted by you is valid and that the issue is spark plug fouling due to excessive engine oil in the combustion chambers resulting from abnormal cylinder/piston wear. You now know that you must check your engine oil level and all other engine compartment fluids periodically and I hope you will remember this when you buy your next car, whatever it may be, and no matter how new or old that car is.

Even if your car has a perfect engine, how do you know that the engine oil level is correct after the lowest-paid individual in the service department changed the oil - if you don't bother to check the oil level yourself? And since we live in an imperfect world, you need to realize that engines typically will consume some oil especially after you log 100K+ miles, not to mention whether or not the engine oil was properly filled by the mechanic.

Worn spark plugs would cause engine misfire symptoms but would not cause the severe engine damage that you have described, at least not at 165K miles which is only 45K miles past the normal schedule and 15K miles past the schedule for California vehicles.

A remanufactured engine will probably cost more than a new engine block. You can buy a new engine block for $1,335 plus shipping here:
2007 Toyota Prius Parts - AutoNation Toyota Gulf Freeway Parts

However a substantial labor charge is required to remove the old engine, transplant the cylinder head and intake/exhaust manifolds from the old engine to the new engine block, and there will be a charge to replace parts like the engine coolant pump, thermostat, serpentine drive belt, idler pulley, timing chain, cylinder head gasket, valve cover gasket, oil pan gasket, oil pump front cover assembly, PCV valve, intake and exhaust manifold gaskets etc. with new parts. Some of those parts are consumables and with the others, it makes no sense to reuse old parts with 165K miles logged. Further, when the cylinder head is removed, maybe the mechanic will determine that the head needs to be rebuilt, which will require a substantial machine shop charge, maybe another $1K.

Also consider the market value of your 2007 Prius and think about whether it makes sense to spend $5K+ on a new or remanufactured engine plus the associated labor charge.

If you can find a competent independent trained on Toyota hybrids or at least specializing in Toyota vehicles, with access to Toyota Techstream or equivalent and the factory repair manual info, that would constitute a reasonable dealer service alternative. Maybe you can get a used engine installed for $2K - $2.5K total. Obviously you bear the risk regarding how long the used engine will last but if you get an engine with low miles that should be a reasonable risk to assume - unless the prior owner thought like you that the engine oil level could be ignored.

 

Spark plugs $40 for 4 online (not sure why they needed to change this again)
Ignition coils - $77 each online (all 4 are bad?)

Parts will be $350

Make sure you get a good warranty on the $1500 repair. Make sure that'll fix your problem.

 

Has any garage performed a cylinder leak down test on the ICE to positively identify failed or failing ICE components due to oil starvation or other mechanical defect? I don't understand how one shop can indicate one symptom and the other something completely different unless one or the other has done more sophisticated diagnostic testing. $1525 for 4 plugs and 4 coils, is better than $4k but all the same, WOW! I'm not sure what your DIY skill sets are but if in fact the plugs and the coils are your issues you can teach yourself a $1200 lesson pretty quickly. There are plenty of How-To's on here and Youtube for inspiration. Good luck!

 

at $1500, I just feel there has to be more to it. I can't imagine a 1 hour job being $1200 in labor charges

 

if it fixes the problem, i think you did well. all the best!

 

I am going to say it.... I know all that matters is you have your car back and it runs fine now and blah blah blah but, WHAT THE $*!)& did you just pay ?!?!

That repair shop charged you $1,525 to replace the iridium spark plugs and your ignition coils!?! Seriously?

That can be done by a basic DIY'er for under $200. I suppose I come from a different world, but even for testing fuel pressure and other small things, $1,525 is on the insane end of high. I wouldn't ever return to that shop, even if Jesus was the mechanic himself I also wouldn't tell anybody - your neighbors, in-laws, boss/co-workers, or friends what you just paid for basically a full modern day tune-up, unless you enjoy being ridiculed.

Of course, I realize not as bad as the highway robbery the dealership was trying to attempt...but still. I had to say what I did. Happy your car is fixed for less than the $4000 or whatever the dealership quoted, but damn.

 

Now I'm going to say it.

Nooooo, they charged $1091 (plus env chrg and tax) to fix the problem. They charged $351 to find out what to fix. They also threw in $1500 of diagnostic time as a goodwill gesture and had 4 of their guys (including the owner) looking at the problem to come up with their diagnosis.

It's all good and well to say :

but unless you know what to fix you're up s#!t creek without a paddle. In my experience you pay your professional for their knowledge and skill. If I had that myself I could save a whole lot, but I don't so I pay someone who does. BTW, seeing as the basic parts are $305 (by JC's reckoning and $753 by the shop's), I don't see how you arrive at $200.

There is no shame or ridicule in paying someone for their knowledge if you don't possess the skills or knowledge yourself.

The only thing that I agree with you is that it seems that it took them an insane amount of time to reach their diagnosis. It seems that the repair shop agrees by throwing in $1500 of diagnosis for free.

I also agree with JC, there is probably more to it that it seems on the face of it.

Just my $0.02 worth.