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Stumble at idle post TB and Injector cleaning

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by rodri9o, Oct 26, 2020.

  1. rodri9o

    rodri9o Junior Member

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    Hi All!

    My 06 Prius is up to 252,000 miles!

    Last week I got in the Prius to go to work in the morning and it was idling really REALLY rough where it sounded like a jack hammer under the hood! I let it sit and eventually it stopped after warming up. After going through this in the morning for a few days after the car sat overnight, I finally got a check engine light: Cyl misfire 3, cyl misfire 4, general cyl misfire.

    So, thinking the car has so much mileage, and I replaced plugs and coils back in April of 2020, I went and had the injectors cleaned and reinstalled. Prius ran even better, but still had an occasional shudder and rough idle for moments at a time.

    I went and cleaned the TB in place with spray and rags and cleaned the MAF with MAF spray, put it all back together. Went for a spin and for the first 30 min it was idling high, then low, then high again. I parked it and pulled the black terminal on the starter battery for about 20 min...thinking it would clear the memory of the TB position?

    After battery was hooked up, I reset the auto window and radio pre-sets....and the idle was now normal. Car ran really really well and I went and did and changed the oil (it was time). I thought I had it all resolved!!

    I got in it this morning and it stumbled/shuddered again! very lightly, no engine lights, but still shudders!

    Do I need a new MAF?

    I'm hoping it is not a fuel pump....

    Any advice?
     
  2. mr_guy_mann

    mr_guy_mann Senior Member

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    One way to check the MAF is to use a scantool (or Torque app and adapter) to look at fuel trim data in the engine computer while the engine is operating properly. Fuel trim is the computer's adjustment to fuel injection on time based on the signal from the oxygen sensor (air-fuel sensor).

    Normally the short term trim cycles near 0%, + or - 2%. If short term is too far from 0 then long term trim will try and correct that to bring short term back to 0. Short term plus long term equals total trim. I usually see total trim on a Prius at 5% or less (near perfect) but anything at +/- 10% range won't cause me concern.

    If the MAF sensor is bad (misreporting the actual airflow) then the ecm will make the wrong calculation for injector on time. The oxygen sensor will respond and fuel trim numbers will hsve to make a big shift (over +/- 10 or 20%). So large fuel trim numbers MIGHT indicate a problem with the MAF. Or it it could be any if a dozen other things that could affect fuek mixture - injectors, vacuum leak, exhaust leak, injectirs, fuel pressure, temperature sensor, wiring problem, etc.

    As far as misfire on starup. There are acouple of other possibilities as well. You could have sticking valves, or maybe a seeping head gasket( not common on Gen2 but it could happen).

    Posted via the PriusChat mobile app.
     
  3. JC91006

    JC91006 Senior Member

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    You should just disconnect the 12v battery after you clean your MAF and throttle body. Reconnect after a minute and the car should run fine.
     
  4. mr_guy_mann

    mr_guy_mann Senior Member

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    The OP already did a battery disconnect, reports normal idle speed.

    Posted via the PriusChat mobile app.
     
  5. JC91006

    JC91006 Senior Member

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    If it's shuddering while you're driving, it may be many issues. Bad plugs, coils, transaxle.....all kinds of stuff. You should have codes
     
  6. rodri9o

    rodri9o Junior Member

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    Well, to update here (it's been a while) I ended up removing the throttle body, intake manifold and saw some CRAZY stuff in there: a coating of oily crud....black, sooty, and looked like tar! GROSS!!

    Here's what I ended up doing:

    -Firstly the throttle body was so cakes up with crud on the intake side that I went through a can of carb cleaner and scrubbed it all out... and it same out MINT!

    -Secondly, I had the intake manifold SOAKING, stuffed with rags in brake cleaner to remove all of the soot and oil varnish that was build up in the runners!! Just kept spraying and scrubbing as deep into it as I could with brushes until, after 4 cans of brake cleaner, ALL of the aluminum inside was shiney and not coated and clean!

    -Then I looked at the intake ports on the head and they were also cake sup with crud! I soaked a rag in gasoline and stuffed it in each port, then used a paint brush handle to try and remove as much of the oil residue crud from in there!!! I don't think I got all of it, but I'd say I got almost all of it!

    I think I may need to install a catch can??

    In the end it all went back together with new gaskets and and can ran pretty well after. Been through about 3 tanks of techron to hopefully get any of the crud I loosened up in the intake ports that didn't come out...and hopefully some of that worked it's way out. I still get stumble here and there...but it is 90% less frequent than what it was before I pulled everything apart. I'm hoping this is just any last remnants working themselves out? Any ideas on what this stumble could be?? Still no CEL's and it runs and drives well...get pretty good mileage for 250k+ (37-42 in stop and go...not much hwy driving in the past 3 months). I may replace the plugs just for the heck of it. The coil packs are about 6 or 7 months old.
     
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  7. rodri9o

    rodri9o Junior Member

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    Thanks for your responses guys!

    I am going to look into the Torque app and the adaptor. What adaptor is needed? I only have a regular OBDII scan tool. I'd love to see what the values are and determine if the MAF is on the fritz.


    Yes, all good calls and also what I thought. The shuddering is (IMO) definitely coming from the engine and it seems like a momentary loss of ignition...like a coil pack gets unplugged for .05 seconds. I will replace the plugs; they are cheap enough and it is easy to do. Coils are not even a year old, but I did not get them from Toyota...maybe the aftermarket coils are crappy?

    No CEL's...I only had misfire codes when the stumbling was really bad but since I did the intense intake plenum cleaning no codes...
     
  8. rodri9o

    rodri9o Junior Member

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    Forgot to mention...still have a stumble from time to time and id like to resolve it.
     
  9. Mendel Leisk

    Mendel Leisk Senior Member

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    This may be just a third gen head gasket thing, but is the engine coolant level stable in the reservoir?

    Cleaning out all the intake crud may do it though. Positive Crankcase Ventilation having negative consequences, lol.
     
  10. bikes4u

    bikes4u Member

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    You can unplug your EGR and see if still stumble. If it stops stumble your EGR is clogging
    Posted via the PriusChat mobile app.
     
  11. edthefox5

    edthefox5 Senior Member

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    G2 engine does not use egr.

    Oily crud is coming from the engine via the Pcv valve.
    Your engine must be eating alot of oil and has very bad blow by.
    What brand oil do you use?

    The G2 engine is an extremely clean running engine and will not suffer Toyota ring clogging either if high quality oil is used throughout its life with a decent OCI.
     
  12. rodri9o

    rodri9o Junior Member

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    I've always used Castrol high mileage. Always at 3000 miles....sometimes 4000 when pressed for time.

    So, do i understand it correctly that the blow by is what may well be causing the stumbles?

    Guess if thats it, then its an engine teardown and new rings??
     
  13. edthefox5

    edthefox5 Senior Member

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    Yes it has extreme blow by based on what your seeing. You pulled the 2 rubber hoses off the throttle body you saw all the gunk in the hose right

    you can confirm this by taking the valve cover off and see how bad it is in there.

    how long have you owned the car?
     
  14. mr_guy_mann

    mr_guy_mann Senior Member

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    A stumble is most likely an occasional misfire- not enough to set a code but you can still feel it. Possible causes can be: sticky valve, weak valve spring, marginal compression, weak ignition coil, uneven injector flow or poor spray pattern, intake valve deposits (when you were cleaning, did you gett all the carbon off the valves- down to bare metal?), ingesting a slug of pooled oil from the intake, etc etc.
    How much time and money do you want to invest to try and fix this?

    Posted via the PriusChat mobile app.
     
  15. rodri9o

    rodri9o Junior Member

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    You know what....I'm an idiot...I didn't clean the damn hoses:censored::censored::censored: I didnt notice any gook coming out of them, but then again I didnt look....just disconnected and re-connected.

    I guess that's the next step is seeing what it is like in there...

    I got the car in Feb of 2018 with 192k just to commute and put on about 500+ miles per week for about 1 year. Once I got the car, I 9 changed plugs, oil and trans fluid and just drove it on 91 or 93 octane with an occasional Techron fuel system or injector treatment every few months. Currently at 253,000 miles.
     
  16. rodri9o

    rodri9o Junior Member

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    sticky valve - Is there a check for this?

    weak valve spring - Is there a check for this? I may well be pulling the valve cover off (see above responce to edthefox)

    marginal compression - I could throw a tester on it, but when it iddles the car doesn't stumble consistently...just periodically. It does seem to happen more when the car is cold, but sometimes happens when warm.

    weak ignition coil - the ignition coils I replaced with were not OEM...should I install OEM ones?

    uneven injector flow or poor spray pattern - Had the injectors cleaned about 1.5 months ago, tested and new o-rings.

    intake valve deposits (when you were cleaning, did you get all the carbon off the valves- down to bare metal?) - I tried all I could to get the valves cleaned but it was so hard to reach in there. They looked clean and without the oil residue crud from where I saw, but the opposite side I could not see.

    ingesting a slug of pooled oil from the intake - Intake was cleaned out and used bout 4 cans of brake clean to get the inside of it back to silver aluminum....it was all black/tarred inside. I will check (once sun comes up) if there is still oil pooled up in the intake manifold.
     
  17. rodri9o

    rodri9o Junior Member

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    Engine coolant has been stable the entire time. It seems a catch can for the PCV crud would be a good thing to install once this stumble is resolved.
     
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  18. rodri9o

    rodri9o Junior Member

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    Well...I just went outside, pulled the filter cover and opened the TB plate. Peeked in there with a flashlight and saw some golden colored oil pooled up in my nicely cleaned manifold....

    (n)o_Oo_O

    Sure hope this isn't the end of my lil'Prius:cry::cry::cry:
     
  19. Mendel Leisk

    Mendel Leisk Senior Member

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    That's normal sans oil catch can. An effective can will reduce that by 80~90 percent. It won't completely dispel but helps a lot. Some stuff still slips through, and I think a bit of oil is also being spit back out of the intake ports; I've seen that when I'd cleaned the intake, then removed intake again just a few weeks later.
     
  20. edthefox5

    edthefox5 Senior Member

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    Sounds like you did a good job on the oil but previous owner did not take very good care of it probably Dino oil at the dealer with poor oci.

    if you open the throttle body butterfly and look in there there’s always a big pool of oil in the bottom there it’s part of the Atkinson cycle weirdness that and the big plenum chamber in the intake manifold.

    given how nasty the oil was be aware there’s a small oil filter used for the vvt cam system. It uses oil pressure to advance ignition timing.that oil filter will be very clogged. Right beneath cylinder #1 is a hex head bolt. There’s a little inline filter behind that bolt it will be very clogged. Use a high quality hex tool that bolt is on really tight you have one chance of getting it out. I did a write up on it years ago use search forums link up top and search:

    VVT FILTER

    I’ll see if I can find it I listed the hex tool size.

    the deciding factor on the motors health is how much oil it eats between oil changes but at that mileage and a poor oil change oci from previous owner that may be a moot point. As far as the cops I’m not a fan of replacing denso electronics with after market parts as most after market parts are China crap
    IMHO.
    Keep an eye out for a new motor we see many G2 motors replaced on this site, lots of info.
    Good luck.