Acceleration issue after EGR maintenance

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by wasperjaws, Nov 5, 2019.

  1. wasperjaws

    wasperjaws New Member

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    2010 with 138500k mi.

    Last week I had the typical "rough start" on a cold morning and a check engine light came on. I can't remember the exact code right now (something like P0304 maybe) but it indicated a problem with cylinder 4. So after lurking the boards for a few days (I had been here before to learn the ins and outs of a DIY oil change and transmission drain/fill) and watching the awesome Nutz About Bolts videos, I performed a lot of the suggested maintenance on my Prius this past weekend.

    I changed the spark plugs, cleaned the EGR cooler, pipe, and throttle body, cleaned the intake manifold, and replaced the PCV valve. Everything went pretty smoothly besides losing a decent amount of coolant, which I replaced. I will change all the coolant soon since it's past due.

    After I got it all back together I started it in maintenance mode and it ran rough for about 30 seconds before smoothing out. Then I got some white smoke out of the exhaust (none from the engine) for a minute. I drove it around the neighborhood and everything cleared up and seemed fine.

    Today I drove it to work and had it on the highway for the first time and noticed an obvious acceleration issue trying to get up to hwy speed. The best way I can describe it is it felt like I was driving a manual transmission and was in too high of a gear. It was accelerating, but slowly. After slowing down, I floored it to see how it would react and it again accelerated slowly as it again felt like the transmission was in the wrong gear. (I know the CVT doesn't work like a regular transmission, I'm just trying to describe how it felt.) I kept it floored until I hit 80mph when it finally "shifted" and felt correct and smoothed out. I went down to 65mph (typical speed driving to work) and put it on cruise and everything felt normal. When I got off the hwy I experimented with accelerating from stops in ECO mode and PWR mode and both were very quick.

    Any ideas on what might cause this? Did I forget to plug something in?
     
  2. wasperjaws

    wasperjaws New Member

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    I should also mention another symptom was that it used oil. I don't know how many quarts per mile but it was a decent amount.
     
  3. tankyuong

    tankyuong Senior Member

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    Sounds like a blown head gasket
     
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  4. bisco

    bisco cookie crumbler

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    welcome!
    no codes?
     
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  5. wasperjaws

    wasperjaws New Member

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    I haven’t been able to get codes yet but can tomorrow.
     
  6. wasperjaws

    wasperjaws New Member

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    Got the CEL scan today, it's a code for the MAF. I believe on another thread @NutzAboutBolts said this was an easy thing to forget to plug back in.
     
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  7. Pluggo

    Pluggo Active Member

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  8. wasperjaws

    wasperjaws New Member

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    After I came on here to locate the MAF sensor and then plugged it back in everything is back to normal. The CEL light is still on so hopefully that goes off after a few starts.
     
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  9. Mendel Leisk

    Mendel Leisk Titanic Social Director

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    So was it the MAF (Mass Air Flow) sensor being unplugged? It's connector is on the back side of the large air tube heading to the throttle body.

    I'm not sure though, that disconnected MAF would cause that acceleration problem. Anyway...

    There's also the MAP (Manifold Absolute Pressure sensor, it's just below throttle body, on right side (as you stand at front of engine bay).

    If there's a disconnection, or some sort of glitch, it can take 5 or 6 start ups for the CEL (Check Engine Light) to clear.
     
  10. NutzAboutBolts

    NutzAboutBolts Senior Member

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    If your vehicle wasn’t experiencing any of the symptoms before the maintenance, and then you got a CEL, that’s mostly the cause of the problem. A bad MAF sensor can cause issues with engine performance since the ECU detects the air and fuel ratio that’s coming in. Hopefully that’s the only issue you got. If you got the P0304, it’s a misfire in cylinder 4, you should get that checked out as well.
     
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  11. wasperjaws

    wasperjaws New Member

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    Thanks for your replies. As soon as I plugged in the MAF it ran like normal. I initially had the P0304 but it went away after I changed the plugs.
     
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  12. Mendel Leisk

    Mendel Leisk Titanic Social Director

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    It's sooo easy to forget to reconnect the MAF sensor. You're just about done, just got the air box and tubing reinstalled, the connector for the MAF is hidden behind. Should tie an orange ribbon to it when disconnecting. (y)
     
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  13. wasperjaws

    wasperjaws New Member

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    Thought I would update everyone. I expected the CEL light to go off but it has stayed on. I got it scanned today and now it's reading P0403 - exhaust gas recirculation control circuit. I'm going to disconnect the battery to clear this and see if it is a leftover code or something. I know I got everything cleaned well so not sure what could be causing this.
     
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  14. wasperjaws

    wasperjaws New Member

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    I disconnected the battery for a few minutes to clear the code. When I started it back up the CE light came on as soon as the ICE started up. It's still the code for EGR. Not sure where to begin trying to find out what's wrong. Since the code wasn't on before I started the work it doesn't seem like the EGR needs to be replaced. Is it possible to damage it while cleaning? I used Purple Power and a pressure washer. My gas mileage seems to be slightly lower than before I performed the maintenance, but it's also gotten kinda cold around here so maybe that's affecting it. Anyway, if anyone has any suggestions I'd appreciate it!
     
  15. Mendel Leisk

    Mendel Leisk Titanic Social Director

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    If all the passageways are clear, all I can think of is the EGR valve is not working properly. Did you disassemble it, take off the black plastic cap?
     
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  16. Mendel Leisk

    Mendel Leisk Titanic Social Director

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    Any chance it's a cleaning rag left in one of the passages???
     
  17. wasperjaws

    wasperjaws New Member

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    I don't remember if I took off the black plastic cap or not! I knew I should've taken pictures along the way. I guess all I can do is get back it back off and make sure there's no visible problem, then replace it if needed.
     
  18. wasperjaws

    wasperjaws New Member

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    Now that I've looked up the part I should clarify: I only pressure washed the cooler. I cleaned the EGR valve with brake cleaner or something like that.
     
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  19. Mendel Leisk

    Mendel Leisk Titanic Social Director

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    Yeah same here. I don't think you'd forget taking that apart. I tried tapping the hold-down screws on the black cap with an impact screw driver. They were starting to chew up so I stopped (like the fox and the grapes). I found was able to clean it fairly without further disassembly.

    No bent pins on the egr valve electrical connector?

    You cleared the EGR passageways on the intake manifold?

    Other'n that, a puzzler. (n) <intended to be a head-scratching emoticon
     
  20. wheezyglider

    wheezyglider Member

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    Is the code still P0403 and only that?
     
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