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Discussion Starter · #1 ·
I have a 2003 tundra 3.4L v6 sr5, I just bought it 2 weeks ago. My first gas fill was 93 octane which lasted about a week, and my second fill was 87 octane. I don't know if the 87 octane could be the cause.. but this problem started to happen a couple days after. So a day after when it was half tank I filled It up with 93 again hope that the problem would go away but it still hasn't. I just wanto be details as possible. also the check engne light is on. evertime I accelerate.. Either from stop light or while already moving fast like on the express way, the car struggles to accelerate and the check engine light flashes. I feel the engine rumbling and shaking and it's taking the car a lot longer to speed up. It lasts about 6 seconds or so and the car cold run normal agan or it starts to do it again when I accelerate. And now when I brake to a stop the I feel the engine shake a choke or something but it never turns off. I haven't done anything yet but I suspect fuel filter or maybe spark plug lines? Hope you guys can help me out. Thanks
 

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Definitely get the codes read for free at Autozone and then post back here. Without the codes you are shooting in the dark.

Initially I would clean the MAF and Throttle Body, check the plugs and coils, and make sure the fuel filter is not clogged. I have read that it is very very rare for a fuel filter to be clogged on these trucks because Toyota engineers over-engineered them but it could be possible that you pump some sediment into the tank.

Check you air filter as well. Get the codes first and that will help tremendously in tracking down the culprit and fixing the problem.
 

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and do it fast..the flashing check engine light means an emissions related/misfiring situation that will damage the catalytic converter in a hurry....

sounds like a bad engine misfire to me...do what is suggested above, get the codes read ASAP and then if its a misfire start with plugs and wires, then clean the air flow sensor and check fuel flow...
 

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Discussion Starter · #5 ·
Hi guys, finally got the codes read

P0304

Definition
Cylinder 4 misfire detected
probable cause
1. weak/missing spark
2. Plugged fuel injector
3. Engine mechanical fault
4. Large vacuum leak specific to cylinder

can some recommend me the steps to fix this and other things I should do...
Thanks
 

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Look for a vacuum line that has fallen off or cracked. Check your pcv valve, do a compression check (burned Intake valve)
Swap the coil for another cylinder, then swap the injector for another cylinder. I am thinking it's a vacuum leak or valve as
it seems to really be affecting some of the other cylinders.
 

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Discussion Starter · #7 ·
i found the problem, it was a spark plug that was causing it. cylinders 1,3,5 had ngk spark plugs and looked clean. but cylinders 2,4,6 the spark plugs were different and covered in oil. i just replaced all 6 spark plugs with new ngk's and that did the trick. now my check engine light went off on its own.

thanks everyone for all their help.
 
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