Possible throttle body issue

Discussion in 'MZR Knowledgebase' started by Wrestler216, Mar 7, 2021.

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  1. Wrestler216

    Wrestler216 Greenie Member

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    Long story short, my car is currently undrivable as it will barely accelerate up to speed and struggle's up hills.

    While troubleshooting today I noticed while driving and looking at the guages on cobb ap
    accelerator pedal position read correctly from 0-99 while throttle position never went above 32%. Obviously if this is correct it would explain my issues.

    My question is, is there a way to check whether the throttle body is not opening all the way while driving or if the throttle position sensor is reading false and sending the computer bad data causing the issue? Has anyone had a similar issue with the throttle body before?

    Fuel trims are around +10% when driving and at idle. Vacuum is good and the car has practically brand new plugs and coils.
     
    Wrestler216, via a mobile device, Mar 7, 2021
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  2. Sho

    Sho Silver Member

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    Throttle position should go to 76% at WOT. Sounds like a throttle body issue
     
    Sho, via a mobile device, Mar 8, 2021
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  3. Mikey27

    Mikey27 MSM Motorsports Silver Member

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    Does it feel like the pedal has a massive dead spot? Does it feel choppy instead of a smooth transition?
     
    Mikey27, via a mobile device, Mar 8, 2021
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  4. Wrestler216

    Wrestler216 Greenie Member

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    No it feels and drives smooth. Cold starts seem rough though. As soon as the pedal gets to about 30% throttle it's stops accelerating any harder and stays there. Its as if I were barely pressing the pedal down. It will eventually reach the speed limit but struggle's to hold it and loses speed up hills. No cel either. I swapped in a different maf sensor to see mine was off but that had no effect.

    I thought it could be a fuse as I had a short to the wiring harness but they all tested good for voltage and continuity. Battery has good voltage too.
     
    Wrestler216, via a mobile device, Mar 8, 2021
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  5. Mikey27

    Mikey27 MSM Motorsports Silver Member

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    Doesn't sound like the typical limp mode which is what I was going for.

    Like sho said, tps should go to around 76%

    I suggest you pull the intercooler pipe and look at the throttle body key on engine off while someone presses the pedal in the car.
     
    Mikey27, via a mobile device, Mar 8, 2021
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  6. Wrestler216

    Wrestler216 Greenie Member

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    I just finished doing that actually and the weird thing is it didn't move at all.
    Should it move with key on engine off?

    With the key out and battery disconnected, I was able to manually work it just fine. I attempted to start the car with the intercooler off but it just died. But, I did see the throttle body fully open and close itself about a minute after the car was shut off. I assume this is some kind of computer check.

    It's seems the sensor could be going bad. I looked for one online and didn't find anything, do they not sell them without the throttle body?
     
    Wrestler216, via a mobile device, Mar 8, 2021
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  7. Mikey27

    Mikey27 MSM Motorsports Silver Member

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    I wasn't 100% sure on the actual tps position koeo, so I went to the car currently in my garage to find out (attached), it's 58% that it'll go to. So if you're getting nothing that's not normal.

    Yes, it does actuate the TB after shutdown, that is normal procedure.

    The tps is an integral part of the throttle body and cannot be replaced. http://cloud.tapatalk.com/s/6046c3972e759/20210308_193717.mp4
     
    Mikey27, via a mobile device, Mar 8, 2021
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  8. Wrestler216

    Wrestler216 Greenie Member

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    Update for anyone curious. Ran out of time to troubleshoot and shop says it's a clogged cat which would explain throttle body not being able to open. Going to have to drive without o2 sensor when I get the chance and confirm that's the issue. Looks like it's downpipe time.
     
    Wrestler216, via a mobile device, Mar 13, 2021
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  9. Easter Bunny

    Easter Bunny Professional Engineer Platinum Member

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    That makes no sense at all
     
    Easter Bunny, via a mobile device, Mar 14, 2021
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  10. Sho

    Sho Silver Member

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    Yeah. That doesnt compute. The throttle body would still open to 76-77% at wot with a clogged cat. But youd be down on power big time
     
    Sho, via a mobile device, Mar 15, 2021
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  11. Awafrican

    Awafrican Moderator Silver Member

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    You got some datalogs of the issue?
     
    Awafrican, via a mobile device, Mar 15, 2021
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  12. Wrestler216

    Wrestler216 Greenie Member

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    How so? The car performs like the cat is clogged. It seems to make sense to me the if the exhaust flow was clogged it couldn't flow as much air through and therefore the throttle plate is only opening partially not because it's bad but because that is all the air the engine can use.

    No, I was just looking at live data. I did end up getting a trouble code p0101 but I've swapped in a new maf sensor and it changed nothing. I've read it's possible for an exhaust restriction to mess with maf readings.

    I am down on power a lot. Why would the throttle body open if the engine could not use that air? As far as I understand the throttle body is only opening partially because that's all the air the engine can use at that time because of the restriction.
     
    Last edited by a moderator: Mar 19, 2021
    Wrestler216, via a mobile device, Mar 19, 2021
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  13. Awafrican

    Awafrican Moderator Silver Member

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    Throttle body is linked to your pedal...you put your foot down the ecu tells it to open. As it's electronic. Sure clogged cat could restrictic exhaust flow and thus flow through the engine but throttle body will still open as you're telling it to because you're giving it throttle.
     
    Awafrican, via a mobile device, Mar 19, 2021
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  14. Duey1083

    Duey1083 Gold Member

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    You probably triggered the MAF code when you tried to start the car with the intercooler off the car.

    The MAF wouldn't have been reading anything when you started the car.

    EDIT: your MAF would have read 0 g/s when you started your car...whatever that translates to in MAF voltage.
     
    Duey1083, via a Samsung mobile device, Mar 19, 2021
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  15. Sho

    Sho Silver Member

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    With key on and engine off floor it and look at the live data. If the TB doesnt open to 76%, its not a clogged cat and the TB is bad ....
     
    Sho, via a mobile device, Mar 19, 2021
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  16. Mikey27

    Mikey27 MSM Motorsports Silver Member

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    You get 76%?

    As I posted above koeo I get 58%...
     
    Mikey27, via a mobile device, Mar 20, 2021
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  17. Easter Bunny

    Easter Bunny Professional Engineer Platinum Member

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    That's why we are saying there is a problem with your throttle body
     
    Easter Bunny, via a mobile device, Mar 20, 2021
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  18. Mikey27

    Mikey27 MSM Motorsports Silver Member

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    I'm not the op...

    But why I question it is because of tables like this one, and how one of my cars also acts koeo(above). [​IMG]
     
    Mikey27, via a mobile device, Mar 20, 2021
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  19. Easter Bunny

    Easter Bunny Professional Engineer Platinum Member

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    Custom tune?
     
    Easter Bunny, via a mobile device, Mar 20, 2021
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  20. Mikey27

    Mikey27 MSM Motorsports Silver Member

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    The table above is from a stock map file.
    However the car I tested it on had a custom tune.

    You got me thinking though, because I know my tables are a bit different, so I decided to flash a stock tune. Well, this is awkward..... View attachment 20210320_084643.mp4
     
    Mikey27, via a mobile device, Mar 20, 2021
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