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P219a - Rough & Shakey @ all cruise speed

Discussion in 'Gen 3 Prius Technical Discussion' started by PurplePrius, Jan 5, 2021.

  1. PurplePrius

    PurplePrius New Member

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    Hello:

    New to this forum but member of a few others (Nissan & BMW). Thought I would ask those that may have experienced what I about about to describe. Currently have 155k on our Prius Persona and have only done routine oil changes, plugs, breaks, and transmission fluid change. About a month or so ago, I noticed a rough acceleration issue that was acting like the car was misfiring. It was generated at speed from 20-35 but did not persist so I didn't scan the car. Fast forward to a few days before Christmas, now after warm up, it runs as if the car is misfiring (20+ to 70 mph) at cruising. Pulled the codes, only p219a was showing, diagnostics did not show any misfires on any cylinder. Read on this forum, there are issues with EGR & Cooler. Pulled those off, was able to clean EGR, but cooler was clogged even after have Ropple Industries try to vibrasonic clean it. I just replaced with new cooler. Issue still persists. Changed, plugs, issue still persists with P219a. I clean everything except intake, which I will most likely do next. Have been reading about blow head gaskets but have no coolant loss or fluid in oil. Not sure where to go from here. Have seen everything from pulling heads for valve clearance, A/F sensors, MAF sensors, etc. The car accelerates fantastic, you don't feel any miss or power loss, not overheating, just the P219a and rough cruising speed. I have also run a full bottle of techcron and just added 93 octane fuel. Banging my head here, definitely don't wont to involve the dealer as they tend to experiment to find the issue.

    Has anyone else had this issue? What was the resolution?
     
  2. mr_guy_mann

    mr_guy_mann Senior Member

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    All right. So in normal operation all 4 cylinders operate equally, and the engine computer uses the signal from the upstream air fuel sensor (AFS) to measure and correct the fuel mixture. This is Fuel Trim and is applied to all cylinders. Short Term trim (STFT) is an immediate response and its goal is to keep the AFS centered on whatever the target mixture happens to be. Positive trim is fuel being added to the "base injector on-time" for those operating conditions. Negative trim is fuel being removed.

    Next is Long Term trim (LTFT) . Its goal is to keep STFT centered near 0. If STFT moves away up or down for too long then LTFT makes a correction and keeps it in memory. (example- if there is a slight vacuum leak and STFT goes to +10% at idle, eventually LTFT will go to +10% while STFT returns to near 0). STFT plus LTFT equals TOTAL FUEL TRIM, which is the full correction to fuel injector on time.

    What does this have to do with your code? Well, fuel trim is applied to all 4 cylinders. The feds decided that car makers had to keep tabs on individual cylinders. So the the computer can look at the AFS signal and figure out what the mixture is from which cylinder and can adjust the fuel trim for that specific cylinder. If the fuel trim for any one cylinder varies by more than 15% from the others, the ecu will set a P219a code.

    SO, really ANYTHING that affects what comes out of a cylinder's exhaust port (ie, the exhaust gas mixture that is sampled by the AFS) can cause this. Compression, valve function, ignition, injectors, exhaust leak at the manifold, etc. Injector problems near the top of the list BUT THAT WOULD BE A GUESS! It will be difficult to diagnose a problem that is symptomatic only at cruise.

    Posted via the PriusChat mobile app.
     
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  3. mjoo

    mjoo Senior Member

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    How can it adjust per cylinder when there aren't 4 separate sets of sensors for each cylinder? Wouldn't you need 4 O2 sensors minimum - one per cylinder?
     
  4. bisco

    bisco cookie crumbler

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    do the intake and get back to us
     
  5. ChapmanF

    ChapmanF Senior Member

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    My 2010 manual doesn't list a P219A. Has it been added in later editions of Gen 3 manual?

    If so, the page with the detection condition and monitor strategy ought to clear up how the system detects it.
     
  6. Mendel Leisk

    Mendel Leisk Senior Member

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    Yeah intake manifold has small Exhaust Gas Recirculation passages, one per port. You can clean the Exhaust Gas Recirculation components till they shine, but until you deal with intake it’s all for naught.

    When cleaning the intake, DON’T disconnect throttle body coolant hoses: there’s more than enough slack that you can lift the throttle body off and just tie to the inverter conduit or whatever.
     
  7. mr_guy_mann

    mr_guy_mann Senior Member

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    This strategy is called Individual Cylinder Fuel Control and was initially rolled out on (some?) 2011 cars, with full implementation a year or two later.

    Posted via the PriusChat mobile app.
     
  8. mr_guy_mann

    mr_guy_mann Senior Member

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    As I understand it, each exhaust gas pulse goes past the AF sensor in order. The ecu makes a deliberate shift in trim to one injector and watches for the response from the AFS. Once it has "synced up" that pulse with a particular cylinder, it just keeps track of the pulses (computers are pretty good at counting and math stuff - Oh, that pulse for cylinder 2 is a bit lean, let's give it +5% and keep an eye on it) I imagine it periodically rechecks its "sync".

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  9. Elektroingenieur

    Elektroingenieur Senior Member

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    Yes, from 2011.
    In two ways, according to the Repair Manual (more info):

    “Air Fuel Ratio Sensor Monitoring Method

    “When the ECM detects an air fuel ratio imbalance between the cylinders based on the fluctuations in air fuel ratio sensor output through all 4 strokes of one cycle (2 rotations of the crankshaft), the ECM determines that there is a malfunction.

    “Crankshaft Position Sensor Monitoring Method

    “The ECM monitors engine speed fluctuations. When the engine speed fluctuates significantly, the ECM judges this as an air fuel ratio imbalance and then determines this as a malfunction.”​
     
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  10. PurplePrius

    PurplePrius New Member

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    Appreciate the responses. I have cleaned the intake and it didn’t look like some of the pics I have seen. I didn’t take any pics. The intake ports on the head weren’t obstructed and and honestly didn’t look bad for 157k. Replaced pcv ( wasn’t stuck). Only noticed a oil residue during intake cleaning. Went ahead and replaced ignition coils. In short no change. Let me clarify what I mean at cruise, the issue doesn’t occur on acceleration or deceleration only when you are applying constant accelerator pressure to maintain speed. On an interesting note. If I unplug egr valve the issue is gone. I recall seeing a post where someone tried the same thing. Running out of option. I can replace injectors but there are no acceleration issues. I purchased the BG Hybrid EPR and try to clean any carbon on rings. Any other ideas here?
     
  11. ChapmanF

    ChapmanF Senior Member

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    If you unplug the EGR valve, the ECM dials the ignition timing way back to protect the engine, and that by itself can change your sense of how the engine is running, so it might not tell you as much as you think.

    Do you have compression or leakdown test results?
     
  12. PurplePrius

    PurplePrius New Member

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    No but will do
     
  13. PurplePrius

    PurplePrius New Member

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    Reached out to a local Prius salvager who advised he was familiar with my situation. He said it was bad news but sounds like a blown head or cracked block. He told me to perform a combustion leak test. This test tool along with test fluid that detects combustion gases in your coolant. Performed the test 3x with no color change. Performed compression test with the following results
    Cyl #1 165
    Cyl#2 160
    Cyl#3 165
    Cyl#4 165


    Going to perform BG Hybrid EPR clean tomorrow
     
  14. mr_guy_mann

    mr_guy_mann Senior Member

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    Hope that includes removing the intake manifold and physically cleaning the EGR passages. As I understand, the gen3 uses individual passages branching out from the EGR valve and cooler to each cylinder. If one or more passages are completely blocked, any chemical system (such as BG) cannot reach that blockage.

    Posted via the PriusChat mobile app.
     
  15. ChapmanF

    ChapmanF Senior Member

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    I'm not seeing how such a chemical would get into the EGR passages even if they weren't blocked.

    I kind of doubt it's the same chemical by the time it turns up in the exhaust.