2011 prius misfire cyl 2

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by ilovetoracecross, May 17, 2019.

  1. ilovetoracecross

    ilovetoracecross Junior Member

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    Hey guys. Heres the scoop.
    2011 prius, 260km. Car picked up a misfire, on cold starting, tripped a CEL, scanner said "misfire in cyl 2".

    Since the plugs had 70000 on them, i got 4 new ones, and a new coil pack for cyl 2. (Since all coil packs were original. )

    Plug 2 whence removed looked a tad lean..

    Pulled the intake manifold et all and cleaned them out. Ditto. On the egr pipe. Sure enough a load of oil in the bottom of the intake manifold, and on the intake runners on the head. More goop on #2 coincidentally.

    Cleaned it all out installed the plugs and pack and intake manifold gasket and.... Started fine. Drove it a bit .. misfire on cold start. Same cylinder, #2.

    Got a new pcv valve, replaced it, noted more goopy oil in the bottom of the intake manifold. In fact given that i had cleaned it all out 3 days prior, a fair amount.

    While this was going on, i i marked the coolant in the reservoir. It was definitely low to begin with, but with no signs of leakage, i didn't know why.

    After the same 3 days or so of driving, it dropped enough to let me conclusively state it was losing coolant somewhere. But where?

    Topped off the coolant reservoir, continued to drive whilst parts arrived and.... Mpgs are up from 40ish to 44.. Wth.

    Some rough starts when cold, but immediately shutting it down and restarting led to no more cels. Rough start btw is NOISY.

    Soo.. im wondering.
    -what diagnostic tests should i run?

    -my computer analysts access is somewhat limited. Non computer analysis equipment accessis stellar. (,I work as a tech at a race car engineering facility, but its vintage only. So we look at the prius and go "fu$#, where'd they put the carbs?")

    I bought a head gasket and timing chain kit, and was planning to put them in Monday night after hours but the better mileage since topping up the coolant reservoir is throwing me for a loop.
    I've a hard time believing thata car that's misfiring due to a coolant weep into cylinder 2 picks up 10 % better fuel economy, you know? Thanks
    -
     
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  2. ilovetoracecross

    ilovetoracecross Junior Member

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    Update.... I did replace pcv valve with a new one. When i checked the intake manifold again, collection of oil under the throttle bottle and intake runners to the valves. Uncertain why a new valve would let that much through
     
  3. Raytheeagle

    Raytheeagle Senior Member

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    You’ve got a blown head gasket. Start planning accordingly;).

    Good luck and keep us posted (y).
     
  4. landspeed

    landspeed Member

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    Soo.. im wondering.
    -what diagnostic tests should i run?

    -my computer analysts access is somewhat limited. Non computer analysis equipment accessis stellar. (,I work as a tech at a race car engineering facility, but its vintage only. So we look at the prius and go "fu$#, where'd they put the carbs?")

    I bought a head gasket and timing chain kit, and was planning to put them in Monday night after hours but the better mileage since topping up the coolant reservoir is throwing me for a loop.
    I've a hard time believing thata car that's misfiring due to a coolant weep into cylinder 2 picks up 10 % better fuel economy, you know? Thanks
    -[/QUOTE]

    Likely a head gasket; I would be tempted to run standard tests such as compression across the cylinders (however, I know there is a special procedure as you can't crank the engine like a normal car). If there is no evidence of a coolant leak it has to be a head gasket.

    It sounds like you have things in order and have the HG coming anyway; please take pics of what you find and post them here. It does sound like a HG leak. I can't really give more advice than that, as you will know what to do given your experience, but if it was me, and I didn't have time, I would probably attach an analogue temp gauge to the engine to keep a close eye while still using it, to prevent catastrophes, given the fact that we don't have a temp gauge!

    I did once drive a car with a cracked cylinder and pressurising cooling system over 1000km, the first 400km with 'full throttle' after repeated 90 degree corners, after performing a 'modification' involving duct tape, silicone sealant, a long tube. With an upside down coke bottle on the top of the windscreen, duct taped to the outside, half full of coolant, and connected to the radiator in place of the expansion tank. The car ran perfectly well like that, but I removed it once I get home as I didn't know what the police would say. :)

    Please keep us posted; I know lots of people with 2009- Priuses and will be asked one day what to do when their HG goes!
     
  5. ilovetoracecross

    ilovetoracecross Junior Member

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    Im suspicious the head gasket is done thus the momentary arrival of a new one.

    Things im stuck on though is the oil residue in the intake manifold after replacing the pcv. I may have just been too honeheaded to clean the hose super thoroughly but its odd none the less.

    And mileage went up 10 % after dumping in additional coolant.

    Any thoughts?

    Ive thus assumed when cold or cooling down enough coolant leaks into #2 to cause a misfire when starting, then it burns/gets dumped out the exhaust, gets hot and expansion seals the leak :/

    Ill definitely try to check the head with the boroscope prior but looks like im prepping for an all nighter monday
     
  6. Mendel Leisk

    Mendel Leisk Sidewalk Supervisor

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    What was the pipe like? At those kms, the (yet unaddressed?) EGR cooler/valve (and intake manifold EGR passages) have likely been clogging up for some time, leading to hotter engine.

    Just like that? Are you an experienced wrencher?

    It's just doing it's job as usual. Look into Oil Catch Cans.

    Yeah likely failed head gasket.
     
  7. landspeed

    landspeed Member

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    I'm no expert - especially as I have only opened the bonnet, once, on an NWH30 Prius. I know they do build up oil and residue, causing blockages and blowing the HG. As to why - I think it is partly due to a design flaw in (the EGR circuit etc), and probably partly related to the fact that Priuses do burn more oil than other cars, due to having 'looser' engines for reduced friction in the engine. Combined with the low viscosity oil. I have read of people installing oil catch cans to the NWH30 Prius, for this very reason. It is something I would do, when I end up getting one, and I can imagine you probably know a lot more than most about those as well!

    I'm not sure about why the mileage went up, except that there is so much computer control that if the ECU is unhappy for any reason, it probably impacts mileage. It could be overheating led the fan running all the time and putting increased load on the electrical system, or it could be overheating causing detonation and reduced mileage after the engine retards the timing / enriches the mixture (I'm not sure exactly what actions it would take with det, but hopefully it would so something - which would end up reducing the mileage).
     
  8. The Critic

    The Critic Resident Critic

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    After the car is sitting for a while, remove the spark plug for cyl #2. You will likely find coolant to be pooled on top of the piston.

    More info and tips can be found in this thread:
    2011 Prius Head Gasket Failure | PriusChat
     
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  9. ilovetoracecross

    ilovetoracecross Junior Member

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    Yes, albeit mostly on vintage A-M, jags, ferrari, and the other stuff our clients race. But we have literally zero idea how the hell this modern thing works, its rather comical.

    EGR pipe was really clogged up. I freed it up, and will pull the whole cooler and valve off to rebuild this go around.

    Re PCV valve i was surprised at the amount that came out after such low mileage. Im wondering if i overfilled the oil or if something else was going on. Oil and coolant getting dumped monday as ill be extra careful post rebuild and will monitor.
    Yes I've seen the catch-can thread, I'll fab one up if it continues and may ponder better placement of it.

    I just really wanted to be sure prior to wasting the time. I do suspect there will be some coolant on top of Piston 2, we'll see what we can see.

    I suspect im correct that the largely intermittent nature would rule out a faulty sensor further upstream?
     
  10. cww180

    cww180 New Member

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    When people say there EGR pipe was clogged up do you mean air would have a hard time going through it? I pulled mine and it had a black film lining on the inside of the pipe but pretty much would serve its purpose for something to flow through it. I just want to make sure if I should be worried about this film that is on the pipe.
     
  11. Mendel Leisk

    Mendel Leisk Sidewalk Supervisor

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    How thick of a buid-up? There's a lot of EGR plumbing upstream of that pipe, that also can clog. The pipe is just easy to check.
     
  12. The Critic

    The Critic Resident Critic

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    A single cylinder misfire will never be caused by a fault air/fuel sensor. A faulty air fuel sensor would affect the entire bank.

    Use an inspection camera to check for coolant on top of cyl 2.
     
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