Need help clearing p0303

Discussion in 'Prius v Care, Maintenance and Troubleshooting' started by SAV man, May 1, 2019.

  1. SAV man

    SAV man New Member

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    I have a 2014 prius with 170k mi with a 2012 motor with 70k miles on it, it is running rough with only a little gas applied at low rpm with a load chatter like an old car trying to die (dieseling) but catches back up to running great once the gas is heavily applied, with no power loss. When I start it, its a little hesitant its hard to tell, runs good, when I get down street around the block it starts this missing chater problem.
    Work performed to solve issue, MAF sensor, Smoke test of evap, Changed spark plugs ( the old ones all had the same burn patterns, used but not the problem), swapped coil pack, swapped injectors and injectors ohm were 12.1 swapped anyway, swapped pcv valve, cleaned EGR pipe wasn't to much build up and made sure EGR plunger was plugin freely, Performed a leak down test and all cylinders were within leak tolerances, Swapped crank/cam sensors. I did not perform coil wire test for the plug showed no signs of foulage, How do I test the ECM and do i need to? I do not know were to go from here can someone HELP???!!!!!
     
  2. The Critic

    The Critic Resident Critic

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    Have you tried cleaning the EGR ports within the intake manifold? What about the EGR cooler?
     
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  3. rjparker

    rjparker Senior Member

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    When you say swapped coils and injectors does that mean you replaced them? If not I would for cylinder 3. A weak hv battery will cause chatter on initial acceleration especially when the hv charge indicator is low. Could be two problems.
     
  4. SAV man

    SAV man New Member

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    The pipe was not bad at all, It didn't need cleaning,but cleaned it anyway. I just put the motor in the car a couple of years ago in 2016 with only 60k on motor, with 20k miles since I installed it. How would the coolant of the EGR isolate cylinder 3? And if it is the EGR how is the car running great for 45 -60 sec with a faulty EGR? Wouldn't it always run shity? I did a compression test and all cylinders hold compression @65-70 psi not the head gasket.I will do the EGR today I guess, Its really weird the car runs great for 60 secs then the ECU is receiving signal from who KNOWS were, telling the car to run like shit. This is why I am thinking its the ECU how would I know if it is? is there a sensor for the sensors? I am a Cabinet worker by trade so I this is only one of my many hobbies,thank you for the input.
     
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  5. SAV man

    SAV man New Member

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    I stripped all part, in working order from the motor I pulled, so I have several extra parts they all work. I even swapped coil packs on the car first, the problem did not fallow the coil pack, it stayed specific p0303 cylinder 3 miss fire. whats crazy is the misfire is not noticeable until the car has been running for 60 seconds then you notice the misfire, so for 60 sec upon start up no misfire drives great. Shouldn't I be ale to Isolate what signals the computer is receiving and when? And if so how do I do that?
     
    #5 SAV man, May 2, 2019
    Last edited: May 2, 2019
  6. bisco

    bisco cookie crumbler

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    welcome!
    have you checked the service manual?
     
  7. cnc97

    cnc97 Senior Member

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    That is not enough compression. The min spec is here.

    Standard compression pressure:
    1373 kPa (14.0 kgf/cm2, 199 psi) or more Minimum pressure:
    1079 kPa (11.0 kgf/cm2, 157 psi)
    Pressure difference between each cylinder:

    Sounds like the ICE is worn out.
     
  8. The Critic

    The Critic Resident Critic

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    I suggest a compression test and a leakdown test.
    I don't think your compression test was done properly. 65-70 psi is very low and would cause misfires on the other cylinders as well. @cnc97 listed the values you should be seeing for this engine and I highly doubt that a 60k mile engine is worn out.

    I am curious if the misfires start right away but take a few minutes to really become severe. Do you have access to a scan tool with a decent set of live data pid's? A lot of things can change during engine warm up - injector duty cycles change, cam timing changes, engines can/will go into closed loop, egr behavior changes, etc. As a general starting point you need to find a way to record data from the relevant pid's and find out what exactly is happening when the misfires start (or become more severe).
     
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  9. rjparker

    rjparker Senior Member

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    Many of the most baffling problems are the result of assumptions that incorrectly validated a component when it was actually bad or intermittent. You go through the whole process and check off the boxes only to find one of those things that was “checked” was at fault in the end. I have seen P0303s that were actually multiple coils. Hopefully you have checked the misfire counters and have cleared all codes and looked for the newest indication.

    What pro mechanics often do is put a scope on the coil and injector signals. The characteristic waveforms may be distorted or missing on a bad circuit. Often, with experience, they can spot head gasket and timing problems at the same time. Certainly the ecu drives those circuits but is obvoiusly the last item to be replaced, in part because of the setup required.

    I would lean against an egr problem since you have inspected it recently. Plus it throws its own codes as do most sensors. Sometimes it pays to have a pro check it with their advanced tools.

    0E43C661-56FF-4D6F-83B8-D4F236A9BEA3.jpeg
     
  10. cnc97

    cnc97 Senior Member

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    If the compression tester was accurate, then compression is leaking past the valves back into the intake and exhaust. I’d try a second test. Techstream will do the test, or you can run it how I did mine. Remove all the plugs and coils, unplug the injectors. Install the gauge unit the first cylinder. Put it in ready mode and hit the gas. The engine spinup will get the job done.

    Try that and report results back here.
     
  11. rjparker

    rjparker Senior Member

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    I will remind you that a weak hv battery will cause chatter on initial acceleration especially when the hv charge indicator is low. See if it goes away from a dead stop with the hv battery showing a full charge. The engine is tuned to require a certain amount of help from the hv battery which goes away if the unit is approaching failure. Mpg usually goes down as well.
     
  12. cnc97

    cnc97 Senior Member

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    I had not thought of that. And you even said that in your earlier post.

    Or, if the engine swap was recent, the damper or clutch plate could have vibrated loose. The chatter of the plate or flywheel could be interpreted as spark knock. The removal of ignition timing by the ICE ecm could cause a misfire when that happens.
     
  13. SAV man

    SAV man New Member

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    Thank you all for the replies and help, I revisited everything, I miss spoke on compression @ 65 more like @165 still did another test and got cylinder 4 to give a compression @130. So as I put everything back together for a quick HV charge I got one of the coils to fail Im thinking of Multiple points of failure. Im going through and working out all suggestions this weekend. And do ANOTHER compression test.... Thank you all for the help!
     
  14. cnc97

    cnc97 Senior Member

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    That’s better compression readings. Try adding a couple of tablespoons of oil to #4. If it comes up then the rings are leaking down. Move an injector from #1to #3. See if the misfire follows the injector. You may find the injector simply wasn’t plugged in properly as well.
     
  15. padroo

    padroo Senior Member

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    It sounds like he is in open loop on startup and then the car goes into closed loop then the misfire starts.
    On startup the car starts in open loop and uses a default strategy until the temperature comes up and then goes into closed loop when it starts taking information from the O2 sensor or whatever Toyota calls it as well as other inputs.
    I can't explain why it is #3 cylinder giving you the problem. Sometimes OBDII reports the wrong cylinder.
     
  16. rjparker

    rjparker Senior Member

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    He said a found a bad coil, probably caused his p0303. Should change them all because the rest have the same history.
     
  17. padroo

    padroo Senior Member

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    This does not sound like the part of a misfire after 60 seconds.
     
  18. mikefocke

    mikefocke Prius v Three 2012, Avalon 2011

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    Could the coil could be heat sensitive. Opening when warm, closed and working when cold.
     
  19. SAV man

    SAV man New Member

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    Ok. was not satisfied with any of the reading, after further inspection found the injecter wasn't seating right, that ended up being my loss of compression, cylinder 4 @ 120lbs added oil and little change @ 125. Made sure the injectors were seated satisfactory the compression went up in cylinder 4 to 157lbs. Put everything back and it now runs like it did good for exactly 57.07 sec then runs the misfire. What do you think?
     
  20. SAV man

    SAV man New Member

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    I think your right. How would I remedy the situation? What is Open Loop and Close Loop? Were do I probe?
     
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