P303 Error (3rd Cylinder Misfire) [Archive] - GrandAmGT.com Forum


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10-18-2004, 08:47 AM
hey guys -

i'm having a ton of problems with my car and i was wondering if maybe you could help me before i drop more money into it. (Grand am 1996, 2.4L 4 cyclinder - 70K miles)

so here's the deal -

about 6 months ago my car wouldn't start. or it woudl start randomly. like it'd turn over but wouldn't do anything from there. so i replaced the sparkplugs and that helped a little but not a lot. i took it into checker to read off the ODBC reader about what error code i was getting - and it said that my Left Bank was running lean. well 4 cyclinders don't have a left bank so i knew something was up.

I started to put 91 octane gas in my car (usually did 87), and put a few cans of that BG42K stuff in it as well.

This helped for a while, but then my car started to 'bounce' a lot when i drove. and it started to chug too, like there wasn't enough gas getting into the system.

so with the help of my boyfriend, i replaced the fuel injectors. my car started up wonderfuly! but the chugging bounce was there.

now, a week later, my car won't start. the check engine light is on wiht the P303 error code (3rd cylinder misfiring). when i try to start it, it occasionally will turn over, but when i try to push the gas pedal to get more gas into the line, it does nothing. i can floor the pedal, and nothing happens.

do you guys have any ideas what's going on? or how i can fix this?

thanks much and if you need more explanation i can totally explain :)

cheers :)

10-18-2004, 10:48 AM

10-18-2004, 10:50 AM
Is that a question or an answer to the problem?

10-18-2004, 11:06 AM
Something to have checked as a cause of the misfire.

manic mechanic
10-18-2004, 03:14 PM
You should check for spark at each cylinder. You can use a calibrated gauge available at most parts stores for a few bucks.

You can also get a noid light and check for an injector pulse at each cylinder. The noid light is also available at most parts stores for a few bucks.

How about fuel pressure? Have you checked to see that you have adequate pressure at the schrader valve on the fuel rail? How long has it been since the fuel filter was changed?

What kind of spark plugs did to you install 6 months ago? Were they the brand and number recommended by the sticker under the hood or in the owner’s manual? Sometimes the parts guys recommend a plug not really suitable for your car, but it's the latest gimmick.

How's that info for a start?

10-18-2004, 03:16 PM
probably a coil pack gone bad