Suddenly getting misfires on all four cylinders

My 2012 Prius V has been a fairly low maintenance car. It has about 117K miles on it, and the biggest issue was that at 103K, I had to do a head job. That is early. The dealer wanted a fortune, so I did the job myself. It was actually pretty easy, but it took quite a while.... Much of this was waiting for the head to be checked and surfaced... I was actually surprised it needed the latter as the car was taken out of service pretty quickly once the bucking started.

Anyhow, at 117K, I've suddenly got misfires on all the cylinders and a code for a random one as well. Originally I thought this was probably bad gas (my daughter bought a tank at a sketchy gas station). I ran the car down to 34 miles remaining and filled it with a known station. I cleared the code and in about 25 cycles there were no errors although the faults were still pending (normal if a fault shows up in 40).

Fast forward to today... Suddenly I have PIDs on all 4 cylinders and the random PID again. I'm mystified. I changed all the spark plugs just a bit ago (didn't do it when I did the head job because I didn't have them on hand at the time). The coils are all original. However, I'm thinking that it is highly unlikely that all four would fail at the same time (again, *ALL* cylinders are reported as misfiring). I cleaned the EGR galleries on the intake manifold at the head job, and they were actually really clean then. I also cleaned the EGR valve itself at that time.

I don't know if this is helpful or not but.... I think the 'check engine light' came on while my daughter had been driving on the freeway for probably 40 minutes or so. I don't it was right after a cold start (I'm trying to confirm). I can also state that, by and large, I can discern no misfire, unless is is a *very* infrequent hiccup, although I'm not sure if that is a phantom of my imagination, frankly

So, I'm a bit stumped. I'm kind of assuming that the ignition side is probably OK. I'm also thinking that the injectors are probably OK (both for the same reason... all cylinders have PIDs instead of just one). And I'm kind of discounting the EGR simply because I cleaned it all just 15K miles ago... That pretty much leaves fuel, I guess... Maybe the fuel filter?

Any ideas are welcomed!

 

Good question.... Yes, the plugs were OEM, brand new in the box. And, if there is any concern, the gasket/seal kit for the head job was also OEM from a dealer (not a questionable eBay dealer either, where I suspect stuff is counterfeit).

I did NOT have the ability to gap the plugs from the box, though. The plastic tube that protects the electrodes were secured in the box, but unfortunately I couldn't find my gap tool, so I had to wing it and *hope* they were gapped correctly.

 

Coolant level is stable. And I just did an oil change too; there was no water in the oil. I really don't think this is a head issue (although anything is up for grabs), which is what I suspect you are thinking of. Don't get me wrong, though. Everything is fair game to ask about. As for the gapping, that is kind of what I figured, but I couldn't find my gapping gauge anyhow.

I have not pulled the fuel pump assembly so I cannot comment on whether or not there is water in the bottom of the tank (I assume this is what you mean by the "sump". The Toyota has a funny assembly, though, so perhaps you are referring to the whole sender/pump/filter setup?). What do you mean by "dry gas" and how can I do this? I assume you mean I should fill the entire tank with this product, although I am not sure where. I live in a major metropolitan area and the gas I put in should be pretty "fresh." I do go to different stations though

I definitely cleared the codes. They still show up as "pending" because I can't clear that, though. But having the codes become active again before completing 40 cycles is, I believe, only possible if you actually have another misfire session. That is my understanding but I'm always interested to hear if my assumptions are incorrect.

When I did the head job, the whole EGR assembly was off the car. I took the time at that point in time to clean the whole intercooler assembly well *and* the EGR valve itself. I blew the cooler out and, cleaned it, verified there was no build or obstructions, then performed similar maintenance on the EGR valve. I did not (and don't really know how) to confirm that the stepper motor on the EGR valve itself is actually functioning as intended.

The cleaning was done personally so I'm quite confident it was cleaned well. I also personally looked at, and cleaned, the EGR passages within the intake manifold. Frankly, mine were not very dirty. Compared to some of the pictures I've seen of other manifolds, mine were pretty clean. Although there definitely was evidence of use, none of the passages were blocked and the crud coming out was nasty but there wasn't a ton of it.

 

OK, I looked up 'dry gas'. I am guessing you are referring to an additive, such as HEET, which will somehow bind to any water and render it less disruptive than in its native state.... No, I have not done that but I shall get some tomorrow, if I can find it locally.

 

Air Boss: yep, long ago I got my pilot's license (don't actively fly now, but have a Falco in my garage... different story!). I'm aware of the drains and preflight function in an airplane, but I've never seen anything like that in a car.

ed: The plug swap was about 250 miles ago after the first episode of the misfire DTCs. The plugs didn't look bad at all, and I did look down the spark plug tube to where the spark plug resides. There was no oil there and no oil on the exterior of the plugs either. So, I did confirm that the valve cover seals are not leaking. It is amazing how many things you fail to remember to write down in a post until someone asks! It is a great question, though, so thank you for asking about it....

I'm took a LOT of care when I did the head job, so I'm confident that I torqued them properly. I did replace the TTY head bolts (again, forgot to mention that) with OEM bolts during the job, even though the original bolts actually still spec out as being usable, per the Toyota manual.

I haven't done a compression test because, to be honest, I'm not entirely sure what the correct approach is on how you would do this with a hybrid car. Do you remove all the coils from the other spark plugs, etc? Would I be introducing a whole host of DTCs that only confuse things? I'm just not sure. I'm also pretty darned confident that the head is fine. But I'll always qualify that.... We all make mistakes. Surgeons leave gauze, metal bits, etc, in patients on an alarming basis, so I am fully aware that I could have screwed up too. I don't have the tools to 'sniff' the coolant for hydrocarbons (the definitive thing that confirmed the head gasket was bad before... other than the massive bucking bronco of an engine!), but I may end up going over to my favorite shop and ask them to do that if I can't find anything else out. In the meantime, I actually have to deal with a major bubble on the side of the tire that just cropped up. I rotated the tires (fore and aft) when I did the plug/oil change 250 miles or so ago, and the bubble wasn't there. But, it popped up and it *definitely* needs to be fixed. I already have an appointment to have the tire reviewed for warranty replacement tomorrow. I only plan to drive to the shop (local) and that is it... The bubble is about 3.5" in diameter and protrudes about 1/2 to 5/8 of an inch.

Thanks for the info on the gapping.... I probably read that someplace but have forgotten. I'll make sure to remember not to mess with iridium plugs!

 

Thank you. I appreciate the compliment....

To be honest, I didn't think the head job was really very difficult. It just took a lot of time. But it was all very logical. Due to the large number of parts that had to come off, however, it was essential to have a good process for tracking parts though. That included a plethora of small bags that I marked with a Sharpie, and also replacing the bolts/etc after removing them. Even with all of that, though, there were a LOT of parts.... I felt like I was on a journey to Middle Earth or something! LOL

I bought a container of HEET today. I haven't put it in yet because I wanted to wait to see if anyone advised against it. But, in the end, it *is* a gas engine, so I would be a little surprised if this were the case, but ????.

I bought an adapter so I can get down to the plug with a compression tester. I'm hoping I don't need to do this, though, because it is a medium pain to get the plugs out. You have to remove all of that lower windshield cowl stuff. I'm hoping that the HEET fixes the problem, although I'm still not sure how alcohol, the main component of HEET, results in a *removal* of the water. But, it does seem to have good reviews.

 

Well, I thought the HEET had done the trick, but after about 160 miles, I got another set of misfires on all cylinders. Damn! It only seems to happen when my daughter is driving the car, but she says she can discern no ill behavior with the car, acceleration, sounds, etc.

I'm at a loss.... I guess I'll have to take the plugs out and do the compression test. Does someone have the procedure for how this is done on a Hybrid car? I'm also wondering if it makes sense to replace the fuel pump and filter assembly. I know those are 'lifetime' entities, but I'm really searching for what other causes there could be.... Fuel or air seem like the only two things that would suddenly cause problems with all cylinders at the same time, and only periodically. Or... Is 160 miles not enough for me to give the HEET to do its job?

 

Thanks for the info.... It would be a bummer if this were another head gasket problem. I really did take my time and work very carefully. I don't usually "miss" on stuff like this, and I followed all of the steps. Lots of research on it. BUT, I also fully recognize that I'm not perfect. I'm not so arrogant as to say I couldn't screw up. :-(

As for running low on oil. No, this engine has never been abused in any way. It has had a good life, which is why I'm hesitant. The check engine lite only came on one time... I got in one day and the car refused to start. It turned out that the inverter went bad and had to be replaced (fortunately it was under warranty still). Other than that, the only time the maintenance lite came on was if it hit its mileage for maintenance. Up until about 2.5 years ago, it was maintained at a dealer. We then went to a reputable mechanic. More recently, I've taken over much of those tasks.

I can't say I checked the oil regularly before.... I can say that I do now, but I've never had any knowledge of the car eating oil.

 

I am curious about something here.... If the problem is that it is very difficult to get the head gasket done correctly, then it doesn't seem like a short block would help. You'd still need to install the one thing that is difficult, so you'd likely end up in the same boat, wouldn't you? And replacing the short block would really only be needed if the cylinder/pistons were defective in some way, right? I am just trying to better understand the idea behind the short block in this case.

As far as diagnosis.... I know there are several different types of failures. Assuming there is a head gasket issue, I can say that the oil looked fine, so I don't think there is water to oil passage, If there is cylinder to water, then it seems like I should have hydrocarbon incursion in the water. This is how we confirmed the HG problem the first time, actually... But the car was starting very rough then; would the current non-discernable misfire every 160 miles or so be enough to cause measurable hydrocarbons in the coolant?

I can pump up the coolant, I guess, and check with a bore scope. What pressure are you recommending? And are there any other tests that will hopefully give better clarity?

thanks all!