Question about 2005 Chevrolet Impala

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I get a code po300 on a scanner wich says multiple cylinder missfire on a 2000 chevy impala 3.8 engine i have replaced the computer no help any suggestions would be greatly appreciated thanks

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Check and replace the plugs and see if the Spark plug wires need to be replaced too. Make sure the wires don't have any burn marks or arching on the exhaust manifold. The other thing to look for is dirty fuel injector and fuel pressure. Check the fuel pressure at the shredder valve, upon start up there should be 60psi to 65psi and when the engine is running it should drop 5psi. Good luck and hope this helps. keep me posted be glad to help.

Posted on Jun 15, 2009


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Misfire po300

po300 is a code and it means missfire on multiple say it has multiple missfires on cylinder 1,you should check the spark plugs on this cylinder they may need replacing and if so replace all plugs on motor.the other thing to check is injectors to make sure they are being powered up and have good grounds,and are flowing properly and not plugging up with should also check the compression on the motor don`t just do cylinder 1 as a problem could be starting in another even though its telling #1.its also possible you could have a rotor problem on your don`t say what year this is so you should check with mazda if it is a compression problem as they have adjusted their warranty because of rotory engine problems.just some places to start.expensive to repair depends on how much experience you have on working of rotory engines and if you have the proper tools to do the work.some people feel 100. dollars is expensive some are okay with are the only that can determine this but either way you have to find out what the problem is first.

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i can recommend you to RUN the scanner/computer for easy diagnostic and fix it. The electronic vehicle is complicated you have faulty the PCM or BCM.etc.
see the diagram attached.
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Chevy malibu 2001 code po300

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I have a 1999 Chevy Blazer 4.3 . It is running bad . I used an OBD II scanner and it pulled up a PO300 code which suggests a Laundry list of things that could be wrong . ...

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1 Answer

2000 cadilac deville. car runs fine, but when the Air is turned on is feels like it is misfiring and the engine light flashes, does this only when the air is on

Sir if the check engine ligh is flashing that indicates a PO300 code which is a missfire code. To determine which cylinder you will need a scanner to find out. The problem could be a failed sparkplug, a failed ignition module for that bank, a failed injector. At any rate it will require trouble shooting to diagnosis. Wish I could help more. Thank you

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1 Answer

Engine missfire

Get your local garage to put a scanner on the car. The early s-type used to suffer from ignition coil faults. If a fault has been hinted towards a specific coil then swap to a different cylinder and see if the fault follows wich will indicate a coil fault.

Has the vehicle had its spark plugs changed? every 70.000 miles as they tend to fail if left unchanged. Intake manifold requires removing to replace bank 1 plugs.

Also check the small rubber elbow on the end of the plastic beather pipe wich runs throught the intake manifold branches. Elbow is located at the rear of the engine

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Engine lights comes on checked code and po300 comes up

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have you changed oxygen sensors? also check wire and plug on #2 I changed plugs once and got multiple missfires changed 3 plugs to a different brand and it solved the problem

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