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Freshly Rebuilt motor misfiring..

Old 07-02-2019, 02:38 AM
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Default Freshly Rebuilt motor misfiring..

Just bought a rebuilt motor and put into my 2008 Scion tC. I've replaced most Parts along with the motor but I am getting a misfire on All 4 cylinders and it is not running properly.
I've replaced the throttle body, the mass airflow sensor, spark plugs and I'm about to replace the ignition coils.

Can anyone else suggest anything else that I might be missing?


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Old 07-03-2019, 12:46 AM
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What diagnostic codes are you getting?
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Old 07-03-2019, 10:18 AM
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Old 07-03-2019, 10:54 PM
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Is the "Intake Air Temperature Sensor 1" same as MAF sensor?
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Old 07-03-2019, 11:09 PM
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I would I think that it is the same because that's the only sensor I have on my air intake
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Old 07-04-2019, 03:57 AM
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P0301= Engine Cylinder 1 is Misfiring.
P0302= Engine Cylinder 2 is Misfiring.
P0303= Engine Cylinder 3 is Misfiring.
P0304= Engine Cylinder 4 is Misfiring.

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Old 07-05-2019, 03:10 AM
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Well for now I will try the ignition coils when I get them in and we can go from there.... I will check the intake manifold to make sure it's all tight.
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Old 07-12-2019, 01:23 AM
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Update.... still misfiring after the new ignition coils. And I did not notice any kind of leak on the manifold and checked all bolts. I am at a loss right now and the next thing I can think of is the injectors or the fuel pump.
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Old 07-12-2019, 02:09 PM
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Is your replacement MAF sensor OEM or aftermarket?
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Old 07-12-2019, 02:12 PM
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It is a OEM Denso sensor.
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Old 07-12-2019, 02:46 PM
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Did you check the engine coolant temperature sensor? A faulty one might tell your ECU the engine is cold when it's actually hot.
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Old 07-12-2019, 03:12 PM
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Originally Posted by TimsScion07 View Post
... will check the intake manifold to make sure it's all tight.
You probably already did this but also check the vacuum hoses for cracks or splits. You have a evap canister purge valve mounted next to the MAF sensor. A stuck valve can cause a vacuum leak which might throw off your intake air reading. A purge valve test might determine whether it's stuck open or closed.
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Old 07-13-2019, 03:19 AM
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Smoke the intake. I had issues that couldn't be seen after rebuilding our engine and it ended up being a crappy intake manifold gasket leaking air. Found the problem in less than an hour and put a felpro gasket on it.
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Old 07-14-2019, 03:26 AM
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Well I went ahead and changed the intake manifold gasket as it seemed cheaper to start with. Didnt see much change in the running of the motor.... going to change out the purge valve next and keep going from there.... eventually I will change out the right part lol
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