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2002 Prius, P0420, 37.4MPG, Misfires, High RPM

Discussion in 'Generation 1 Prius Discussion' started by vk1, Aug 16, 2020.

  1. vk1

    vk1 New Member

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    Hello All,

    I decided to make a new thread for the issue at hand. This is the continuation of this thread about purchasing the car: Prius Gen1 - to buy or not to buy (2 dead modules) | PriusChat

    Long story short, the car has 214,000 miles. On colder days (55F), the engine shakes when starting the car, and very occasionally throws a misfire code on cylinder 1 and 2.

    Very frequently now, the P0420 code turns on. Besides this, the car gets mileage that is out of spec. I am happy even with the mileage it gets, but I think this is a sign that something is wrong. I just completed a 400-mile trip with the car, I got 37.4MPG average.

    On steep uphill grades, sometimes the car would rev up to 3,400 - 4,000 RPM, all the while barely keeping up with cars going 65/70 MPH. Something feels off about the way the engine runs.

    [​IMG]

    Here is how it runs:



    Things that have been done so far on the car:
    • Throttle body cleaning
    • New spark plugs (Denso SK16R11)
    • Seafoam soak of the combustion chamber, seafoam in crankcase, changed the oil
    • Lots of cataclean in the gas tank
    • Rebuilt battery
    My main questions are:
    1. How do I diagnose and fix the engine? Since the spark plugs were replaced, should I do the injectors? Are there any recommendations for where to send them in Southern California to have them cleaned properly? Are there any guides on how to remove them/install them? That would be helpful. I do not have the paid access to the Toyota repair manuals...
    2. The car has already been smogged when I first got it. What should I do about the catalytic converter? I had someone recommend to me that I take it to Arizona, put a 49-state (federal-compliant) catalytic converter on, and sell it. I can't find any after-market manufacturers that make California-certified catalytic converters. Ideally, I would like to keep the car and get a legal cat. Alternatively, what are my options realistically? Does a 49-state cat perform similarly to a California one? When I got my car smogged the first time, I believe no one checked the numbers on the cat or looked under the car.

    Please let me know your thoughts!
     
    #1 vk1, Aug 16, 2020
    Last edited: Aug 16, 2020
  2. bisco

    bisco cookie crumbler

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    have you tried switching injectors to see if the misfire moves?
     
  3. Josey

    Josey Active Member

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    The next thing I would do is swap the #1 & 2 coils with the 3 & 4 and see if the misfire moves. While you're doing that carefully inspect the wiring and electrical contacts and the like.

    I'd also tell you to check the compression, but on this car I have no idea how one would do it since there is no starter to control. Perhaps others here know something of checking compression.
     
  4. vk1

    vk1 New Member

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    No I have not! Do you know where I can take them to get them cleaned? The thing is, the code appears VERY rarely for the misfire. But when I took it to a mechanic, without scanning it he told me he could hear a misfire.


    2320921020 - Fuel Injector. Injector Set, Fuel - Genuine Toyota Part


    At $180 a piece, I don't want to get 4 new ones as that would put me over $700...

    I'll add checking compression to my list. Can't you just unscrew the sparkplug and put in a compression dial? I can run the starter without having the plugs in.
     
  5. Josey

    Josey Active Member

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    I would not get into injectors just yet. It's much more of a PITA than swapping coils and - probably - checking compression. Start with the simplest and move to the more complicated.

    By far the simplest first thing is to just swap the 1/2 with the 3/4 coils and see if the misfire moves to 3/4 (P0303 & P0304) rather than 1/2 (P0301 & P0302). Cross your fingers as that would be an easy answer, but if nothing changes - you've eliminated the next simplest thing and know to move on. So the next move would be compression.

    Yes, to check compression you pull a plug, thread in the gauge and crank. The only reason I'm not certain about the nitty gritty of how is that you don't control the starter the computer does. On a "normal" car you control the starter with the key (so long as the electricals are in order). Your turn of the key sends the juice to turn the starter and you decide when to turn off the juice to stop the starter.

    I've not had an ICE no start or a need to check compression on my Prius, so I'm just not sure how it works with these. With the computer "deciding" to operate the starter, if you disable fuel delivery and spark (which you should do for a compression check), and turn the key I have no idea what the computer does w/ the starter. If it will just crank it for a while, great. Then do it. Someone who knows will hopefully show up to clarify.
     
    bisco likes this.
  6. vk1

    vk1 New Member

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    Thanks Josey, I just ordered a 4 x Denso 90919-02240 set of coils, for $65. I thought why not just replace all of them to not worry about it. I totally would switch coil 1 with 3, but the misfire code only appears once in a blue moon. I wouldn't reliably be able to trouble shoot it...

    Thanks! I will keep the thread update on if this solves the misfire, and ill do the compression next. For the compression, it doesnt matter that Prius uses the Atinkson Cycle? Atkinson cycle - Wikipedia
     
  7. Josey

    Josey Active Member

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    Unfortunately, I can't answer the Q about checking compression or what it means on an Atkinson cycle engine. It's quite possible that you will need a Techstream to command cranking to test it. And while I''m pretty sure that the compression should be just "normal" (say 150-200 psi) I'm not even sure about that. Hopefully someone else on the boards has an answer.

    I would just mention that the misfire is probably more than once in a blue moon since you say that the car shakes upon start up. But having it be frequently or long lasting enough for the computer to set the code might be the once in a while part. It's not as simple as "computer sees a misfire, so computer sets code" just because if the computer threw out codes every time an anomaly came through the wires today's cars would forever be lit up like Christmas trees. So normally a code is set after X anomaly has been recorded X number of times within X time, or X number of times in X numbers of consecutive drive cycles and the like. If you do get a powerful enough scantool you should be able to access a misfire count for each cylinder. It will be expressed as a percentage and it has to get high enough for the computer to toss out the code. At least, this is how it typically works.
     
  8. dabard051

    dabard051 Tinkerer-in-Charge

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    Perhaps not on the high probability list, but... gasoline quality?
    Try a tank of ethanol-free premium and see if the problem persists.
     
  9. vk1

    vk1 New Member

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    Thank you for the replies... @Josey I replaced the coils. They look good, lost two screws in the process! Had to pull off the air box to find them near the injectors...

    [​IMG]

    Upon cold start the engine still shakes the same:



    And I have this problem when the engine is cold ONLY. Is my transaxle/generator/motor1 okay?




    @dabard051 Will try that! Thanks! I haven't tried anything besides 87 count fuel.


    Transmission pan drop, finally got around to it:

    [​IMG]
    The little strainer arm had black metalic particles all over it. Wiped the whole thing down and replaced the ATF IV fluid.

    The pan before I cleaned it: you can see the particles and sludge on the magnet.
    [​IMG]

    After doing the transmission pan drop, the car shakes a little less while breaking with the generative electric motor. Not sure if at all related.

    Based on the way the old ATF looked and had so many metallic particles, should I get a full transmission flush and drop the pan again? From what I was told, the 5 quarts of ATF in the pan is a small part compared to the 12 quarts in the whole transmission. I am worried however that he dealer would rip me off and not actually flush the transmission, but only drain the pan and refill.
     
  10. Josey

    Josey Active Member

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    (Well, the point of swapping coils was to check it out w/out spending $$, but new ignition components can never hurt...)

    I am not a transmission specialist - and there are transmission specialists. Most mechanics, including those at dealerships, don't know squat about transmissions and even fewer will know the Prius CVTs. That said, every transmission specialist I've ever talked to says NO! to a "transmission flush." Drive it another 2-5K or so and drop the pan again.

    I've never dropped a CVT pan (though I'm also belated in getting to mine on my '03), and don't "understand" then as well as typical automatics. But in a typical automatic, the magnet fuzz is just normal. The particles are not normal. Were they metal particles?

    Whatever issues in the CVT this is going to be unrelated to any rough start-ups. You mentioned cleaning the throttle body, but have you cleaned the MAF sensor? (That's an easy one). And if you hook up your scanner - when you first start the car does the engine coolant temp approximately match the ambient air temps (or whatever the under-hood ambient temps would be if you're, say, sitting in the sun. Watch the coolant temp and see what it does when you start, as the car warms up and then up at full operating temps. Same with the actual air temp sensor - actually with the car cold and not running, those two should be in pretty strong agreement about what the temps are.

    What is the status of the check engine light/misfire codes? And of the problems under load like on hills?