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Random Multiple Cylinder Misfire?

Discussion in 'Gen II Prius Care, Maintenance and Troubleshooting' started by MainePriusGirl, Dec 24, 2011.

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  1. MainePriusGirl

    MainePriusGirl New Member

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    My Prius is a 2005 with 196,000 miles. Last week I had the oil changed and snow tires put on. Today it was 19 degrees. Not sure if any of that matters. This morning, the Check Engine light came on (steady - not flashing), and the car began to sputter when I would accelerate in low gears.

    The local V.I.P. Auto Parts store just ran the codes for me, and came up with a P0300: Random Multiple Cylinder misfire. Specifically, P0301 (cylinder #1 misfire) and P0302 (cylinder #2 misfire).

    They couldn't do any further diagnostics today, but gave me a list of possibilities. They also said the oil level is fine, and they doubt it's the ECM.

    How should I proceed? I'm afraid of running up a huge cost in just diagnostics? One simple thing they suggested was changing the spark plugs. Possibilities for the problem include:

    - short in engine wire harness
    - Connector / connection
    - vacuum hose connection
    - ignition system
    - injector
    - fuel pressure
    - mass air flow meter
    - engine coolant temperature sensor
    - compression pressure
    - valve clearance
    - valve timing
    - PVC hose connection
    - PVC hose
    - ECM

    Help?! Please! :confused:
  2. PrimeRisk

    PrimeRisk New Member

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    The very first thing to do is to check the condition of your 12v battery. A weak battery is the cause of tonnes of issues with the Gen2 Prius. Search the forum for ways to easily test the 12v battery. 2nd, are you sure you have enough fuel in the tank and is there any chance you've got water in the fuel?

    If the battery and fuel checks out, I'd look for moisture where it shouldn't be (like in the sparkplug wells) and damage to the spark plug wires.
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  3. MainePriusGirl

    MainePriusGirl New Member

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    Thank you for the quick reply! I also just read elsewhere that it could be related to "running out of gas, or poor fuel quality." The gas is low, so I"ll put some high-test in now. I suppose there is a chance that some water got in.

    Otherwise, I'll have to wait until Monday to see a mechanic. Terrible timing with the holidays! Thanks for the heads-up on the 12v battery.
  4. seilerts

    seilerts Battery Curmudgeon

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    Check the oil level. Oil change + check engine light = oil overfill.
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  5. MainePriusGirl

    MainePriusGirl New Member

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    I did check the oil level, and it is slightly over. The guy at VIP who ran the codes for me felt that it wasn't sufficiently over-filled to cause a problem. In further digging, it looks like the spark plugs might be a good place to start: A code P0300 may mean that one or more of the following has happened:

    Faulty spark plugs or wires
    Faulty coil (pack)
    Faulty oxygen sensor(s)
    Faulty fuel injector(s)
    Burned exhaust valve
    Faulty catalytic converter(s)
    Stuck/blocked EGR valve / passages
    Faulty camshaft position sensor
    Defective computer
  6. ursle

    ursle Gas miser

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    Keep your receipts from the oil change, they can pay for any damages caused by overfilling the oil. Take it to a dealer and let them replace any parts that are now oil saturated in the maf sensor. Seriously.
    Also let the dealers equipment read the codes, hopefully the dealer will have delt with an overfilled crank case in the Prii before. And welcome to PC :)
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  7. MainePriusGirl

    MainePriusGirl New Member

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    Thank you :cheer2:
  8. PrimeRisk

    PrimeRisk New Member

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    I'd hold off on the high-test fuel, it's not likely to help much of anything. The higher octane fuel just prevents pre-ignition of the fuel in the cylinder. The Prius doesn't have a high-compression engine and you weren't getting a Knock or Ping error code. I would fill up just to make sure you aren't running low on fuel and if you think there is a reason you may have water in the fuel, try one of the commercial gasoline drying additives (like Heet).
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  9. Patrick Wong

    Patrick Wong DIY Enthusiast

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    The iridium spark plug change interval is 120K miles. Unless you know that the plugs have been changed recently, I would agree that the plugs should be replaced now.

    It is also possible that water may have entered the spark plug wells for cyls 1 and 2, causing the misfire.

    I doubt that the 12V battery is causing this particular problem. Good luck.
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  10. fuzzy1

    fuzzy1 Senior Member

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    Before spending much on diagnostics, clear the codes (a ScanGauge is very helpful) and keep track of how often this repeats. Is the sputtering continuing?

    I say this because my older car, a '97 with 160k miles, has experienced two episodes of this without known cause, both clearing on their own. One episode was a year ago, repeating only once the next morning. The other was almost a decade ago. But neither episode produced any more than barely noticeably power issues, and could have been fuel problems.
  11. MainePriusGirl

    MainePriusGirl New Member

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    Thanks everyone. I can't even remember the last time the plugs were changed, if ever. I know...shame on me. I bought this car new in 2004 and it has been very good to me. The guy at V.I.P. also thought it might be the plugs.

    Any suggestions on how to proceed with getting this solved without being totally ripped off? Should I ask them to check specific areas, e.g. 1) double-check the possibility of oil overfill, 2) next, check the plugs, 3)...? Or do I just hand over the car and wait? I'm working on very limited funds, considering I just put over $400 into the car last week. Limited as in either pay the mortgage or fix the car. Ugh.
  12. seilerts

    seilerts Battery Curmudgeon

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    I don't think there is anything serious wrong with your car. It may well be a waste of money to take it to someone right now. Yes, you are due for plugs and a new PCV valve, but I'd give it 90% that the codes were solely from the oil overfill, which caused some oil to get into the intake and cause misfiring. You probably need to drain off at least 1/2 a quart, maybe more. Ideally, the oil level on the dipstick is anywhere from halfway to 3/4 of the way up to the top dimple relative to the bottom one. You can clear the code by disconnecting the battery negative cable for 5 minutes, or try turning the car on (Ready) and off three times in a row before the engine warms up, i.e. Ready, wait 5 seconds, power off, wait 1 minutes, Ready, ...
  13. MainePriusGirl

    MainePriusGirl New Member

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    The oil is actually over the top of the fill line.

    Yesterday when I drove it, it went about 10 miles before the sputtering started. Today it started immediately. I'll try clearing the code, and draining off some oil first. Then plugs are next.

    This forum is awesome, by the way. :rockon:
  14. PrimeRisk

    PrimeRisk New Member

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    I'm not sure that the oil over fill has caused all of these codes to be thrown, but the Prius is very very sensitive to having the crank case over filled and you should get that taken care of immediately. As far as the 12v battery issue goes, due to recent events I am convinced that a weak 12v battery can cause absolutely ANY code or series of codes to be thrown in the Prius which may result in any number of odd behaviors. During my most recent 12v issue diagnosis I'm pretty sure I saw the MFD cursing at me. Check the 12v system anyway!

    I've always had my oil changed at the dealer on the Prius for a couple reasons. 1st, my dealer offers maintenance plans for $100, including tax and disposal fees, I get 4 oil changes, 4 tire rotations, and one other service (wipers or air filter). 2nd, if they over fill the crank case and cause an issue, they're easily on the hook. It can be a bit harder to get Jiffy Lube or the type to take responsibility for issues like you're seeing since they don't logically seem to be related.
  15. MainePriusGirl

    MainePriusGirl New Member

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    This morning, I took the car to the garage that had done the oil change (it's a local family business, supposedly very reputable). When I asked them to check for possible overfill problems first, the response was "oh, it couldn't be that." I figured, being a woman, that I would get that kind of response, i.e. completely dismissed. I had them look at the car anyway, and further diagnostics, according to them, indicates it's either the spark plugs or the coil packs. They quoted me $370 to replace all. Can't afford that right now, and I just spent $400 on snow tires last week!

    Came home and called V.I.P. to get a quote on new spark plugs. They are going to change all of them today for $77. The coil packs are pricey (over $100 each?) and I'm hoping the plugs do the trick.

    Again, thanks everyone. Getting this info gave me some "peace of mind."
  16. seilerts

    seilerts Battery Curmudgeon

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    Don't forget to have them do the PCV at the same time.

    You'd never need to change out more than one coil pack, unless you found water in more than one spark plug well.
  17. uart

    uart Senior Member

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    Get them to check the oil level and drain it to just under the full line before they fit the new spark plugs. You say the oil is just slightly overfilled now, but we don't know how much oil has already been frothed up and drawn into the intake already. It seems like a recurring theme here, people reporting this type of problem just after an oil change. Too much so to be a coincidence.

    BTW. With nearly 200k miles on your Prius you probably should be making fairly regular dip stick checks. Just make sure you check when the car is parked on a level surface and has been switched off for at least 10 minutes (to allow the oil to drain back). You should wipe the stick once and then re-insert it to take a reading. I think it's best to fill it to just shy of the full mark. Better to be a few mm under than to overfill.
  18. Patrick Wong

    Patrick Wong DIY Enthusiast

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    For $77 I question whether your repair shop is going to use the correct Denso or NGK iridium spark plugs. They will probably use a cheaper plug which will not have as long of a service life.
  19. The Critic

    The Critic Resident Critic

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    I really doubt a slight overfill will cause a random cylinder misfire. Logically it does not make sense.

    Starting with the spark plugs makes sense if they have not been replaced before. The coils can be tested individually and replaced as needed. A s long as the plugs are of the correct heat range and type they should be OK for troubleshooting purposes.

    Sent from my MB860 using Tapatalk
  20. edthefox5

    edthefox5 Senior Member

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    I wouldn't have VIP do it I'd have the garage do it.
    Go to an auto parts store and get 4
    Denso SK16R11 or
    NGK IFR5-A11 plugs. $ 12 each. So for the correct 4 plugs the cost is $50 alone.

    Take them to the garage and have them install them and ask them to check for corrosion on the ignitor pack connector ends. That corrosion can be cleaned off the connector ends if not to bad. If so corroded they need to be replaced dealer cost $75 each.
    But if an ignitor has failed the car would run really bad from the get go. You would know it. Worse case the ends are just corroded.

    Then ask the garage to clean the throttle body and MAF. That's easy and takes 5 minutes. Your way way overdue for a throttle body clean and that can cause all kinds of driveability issues. Like all modern cars the throttle body gets pretty sooty. If your curious about that search my old posts as I have a very detailed post on how to clean the throttle body with pictures.

    Your garage should not charge more than $100 for the plugs, and tb cleaning.

    And by the way you are way way overdue for a trans fluid change too. And the cv joints and struts are done too. I'm just a ray of sunshine aren't I?

    Good Luck!
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