P0302, P0300 misfire codes after cleaning Throttle Body and MAF

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by bumblediy, Mar 20, 2016.

  1. bumblediy

    bumblediy New Member

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    Hi all, I have a 2005 Prius with just over 150k miles. Recently I started to feel a slight shudder when I was accelerating, and sometimes when idling. I decided to try to clean the throttle body and MAF sensor. I made sure to use the correct cleaners and was very careful with the MAF sensor. Afterwards, the check engine light came on and Torque found the trouble code P0302. The shuddering also got worse, with some fairly violent shaking on startup. I tried to clean both again and drive the car around for a few miles in case it just needed to burn off some gunk, but after a while I got the codes P0300, P0303, and P0304. Also, the engine light was flashing during parts of the trip. How could I have messed up such basic maintenance? Are there any nearby hoses or connectors I might have disturbed that could be causing this? Any suggestions what I should do about the trouble codes? Much thanks to anyone who tries to help me!
     
  2. JC91006

    JC91006 Senior Member

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    did you plug the MAF sensor back in?
     
  3. bumblediy

    bumblediy New Member

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    Yes, and I made sure it clicked in too.
     
  4. bumblediy

    bumblediy New Member

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    The second cleaning seemed to make it a little worse, but it already got really bad after the first cleaning.
     
  5. JC91006

    JC91006 Senior Member

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    I think your problem was already there when you first started cleaning. How did you clean the throttle body?
     
  6. bumblediy

    bumblediy New Member

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    I removed the MAF sensor, then wrapped some strips of an old t-shirt around a screwdriver and sprayed throttle body cleaner on it. I used that to scrub both sides of the butterfly plate and the walls of the tube.
     
  7. JC91006

    JC91006 Senior Member

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    This shouldn't have have made the problem worse. How long have you had the car? Does it have a clean title?

    There aren't that many problem areas in the Prius. I can see the failure of a single spark plug or single coil....but to have all of them fail at once.....it's not normal

    I would probably do some maintenance on those areas.....the spark plugs are the easiest to change (and should be changed at 150k). Then see if there's improvement. But with multiple misfires....I'm thinking it could be something like fuel injectors or fuel pump
     
  8. bumblediy

    bumblediy New Member

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    Yes, the car has a clean title and I've had it for about three years. I'll look around the forum and try to figure out how to change the spark plugs.
     
  9. JC91006

    JC91006 Senior Member

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    Try cleaning the throttle plate again, just spray some throttle body cleaning fluid on the plate and then wipe clean. Then use a little WD40 to lubricate the plate edges. There is a chance you have a bad throttle body, that would need replacement.
     
  10. S Keith

    S Keith Senior Member

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    I changed an air cleaner on a Honda Civic Hybrid, and all hell broke loose. P030*, flashing CEL, running like crap, etc.

    8X bad plugs (they have 2X per cylinder).

    My theory is the change to the inlet conditions allowed this problem to manifest itself. This may be pure crap, but 8 new plugs, and it ran like a top... they looked horrible... may have been the orginals at > 200K miles.

    I'd check the plugs... particularly if you don't know their history.
     
  11. JC91006

    JC91006 Senior Member

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    You also would want to install the proper OEM plugs, don't use anything aftermarket.

    The plugs are on Amazon for only $7.05 each.
    Denso (3324) SK16R11 Iridium Spark Plug
     
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  12. Mendel Leisk

    Mendel Leisk Senior Member

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    @S Keith Been there, done that. With ours Honda had been equal opportunity: when I pulled them it four Denso in one row, four NGK in the other. Checked the valve clearance at the same time.
     
  13. S Keith

    S Keith Senior Member

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    Same. Denso in rear, NGK in front. I think they come this way. I went all 8 NGK.

    Still need to do the valves.
     
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  14. Mendel Leisk

    Mendel Leisk Senior Member

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    I found to take the valve cover off it helps to take off the dipstick tube. Then you can shift an electrical conduit out of the way better. And of course the dang cowl has to come off.
     
  15. edthefox5

    edthefox5 Senior Member

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    Random misfires sometimes indicate a failed lower bearing assy particularly in a Prius a failed connecting rod usually from one or more low oil events. All the lower end vibration confuses the crank sensor reading.

    The best indicator of that is to ask you how many times have you run the engine oil so low the check engine light came on?
    Its a tough little motor but run the oil low once real good and the upper area of the bearing assy runs dry and burns up. The cylinder walls and upper rod wrist pins are splash lubricated. No oil no splash.
     
  16. bumblediy

    bumblediy New Member

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    I've never had the CEL come on due to low engine oil, although the oil level got close to the low mark on the dipstick once. I've since started keeping a closer eye on the oil level and topping up as needed.
    I'm trying to gather the tools to change the spark plugs right now. They were last changed 60k miles ago.
     
  17. JC91006

    JC91006 Senior Member

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    If the plugs were changed 60k miles ago, they should still be good. The OEM plugs are rated to go 120k miles.

    Has the car over heated recently?
     
  18. bumblediy

    bumblediy New Member

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    I don't think the car has ever overheated, at least I've never seen a CEL related to that. I found some mention of the wiper cowl allowing water to leak into the engine compartment and it was raining pretty hard last week in San Francisco, could that have caused the spark plugs to wear out prematurely?
     
  19. JC91006

    JC91006 Senior Member

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    It's just uncommon to have that many failures at once. Usually that points to problems that are not related to spark plugs. Coils can fail but once again, not that many at once. I don't think your spark plugs are the cause if they only have 60k miles on them
     
  20. bumblediy

    bumblediy New Member

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    Update: Problem seems to be fixed! I removed the ignition coils to look at the spark plugs and the hole that was second from the left (probably the cylinder that the P0302 code refers to) was filled with water and rust. I had all the plugs replaced since they were only $8 each at O'Reilly, cleared the codes, and the car has been running fine with no new codes so far after a 15 mile test drive on the highway. Hopefully I won't end up having to replace any ignition coils as well. The water probably came in through the wiper cowl, a problem mentioned in several posts on this forum and in TSB EG063-05. I plan to caulk the seam to prevent this from happening again. I still find it very strange that the problem appeared in full force only after the throttle body cleaning. Also strange that first it was just the P0302 code, but changed to every cylinder code except for that, but I'm just happy the car is ok for now. Thanks to everyone who took time out of their Sunday to offer suggestions.
     
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