Where can I get a diagnostic chart for MISFIRE CODE 305

[1QWIK6]

2002 Impala, 3800SeriesII V6,75K miles. Misfire code 305. #5 cyl misfires. I changed the plug wires but car still studders and misfires and low RPMS. I'm thinking coil pack, but would like to find a diagnostic chart for a misfire code 305. CAN ANYONE HELP?

 

[gofstbuick]

Is the code generic or manufacturer specific? I would think if you could retrieve, the manufacturer specific code, it will lead you to the problem. Also, can you view freeze frame data? Whatever you do, don't disconnect the battery, as this will not only erase codes, and reset monitors, but you'll also loose freeze frame data. Is the engine light blinking continuously?

 

[1QWIK6]

The "check eng" light is illuminated. Doesn't flash. Misfire code 305 (#5 cyl misfires). The code is not the ROOT CAUSE. Something is causing the misfire code. I need a diagnostic chart to find the problem. Anyone work at a dealship? Can someone Xerox a copy of the code and fax it to me?

 

[gofstbuick]

I have some troubleshooting data, but cannot transfer it to my computer to email you. Can you display some freeze frame data. maybe I can pinpoint a area to concentrate on.

 

[1QWIK6]

I don't have a scan tool. I just brought the car up to AutoZone for them to pull the code.

 

[gofstbuick]

Originally posted by 1QWIK6
I don't have a scan tool. I just brought the car up to AutoZone for them to pull the code.

Bummer.

I would check primary and secondary resistance of the coil first. Is this a waste spark system or coil over plugs? Also, use a spark tester to look at spark firing. Next, check for vacuum leaks. Is the EGR valve near the misfiring cylinder? If so, check that the EGR valve is not leaking or the pintle hanging open. Try those first and get back to me. These are some no cost test to begin with.

 

[Attype]

If the misfire is at idle and clears up with rpm its sounds
like a restricted #5 fuel injector. We run into this on the 2000 and up 3800's at work alot. The only way to be sure is to perform an
injector balance test(special tools needed-tech2 & fuel pressure
guage).
Usually we clean the injectors and its fixed(carbon deposits)
on some we do have to replace.

Hope This Helps

 

[TurboJim]

Originally posted by 1QWIK6
The "check eng" light is illuminated. Doesn't flash. Misfire code 305 (#5 cyl misfires). The code is not the ROOT CAUSE. Something is causing the misfire code. I need a diagnostic chart to find the problem. Anyone work at a dealship? Can someone Xerox a copy of the code and fax it to me?

You need to find the cause of the #5 misfire. Theres no diagnostic chart really. An engine needs air, fuel, spark and compression. If any of these are missing, it will misfire.

Once you know how an engine runs, its really simple to find the cause. I know that sounds elementary, but thats all there really is to it. If it was a coil, you'd have a problem on #2 also, since its a waste spark setup. So I doubt its the coil, you swapped the plug and wire, so I doubt thats it. Next, I woujld swap the #3 and #5 injector and see if you get a P0303 in place of the 305. If so, its cut and dry, the injector is bad. BUJT, knowing what I know about the 3800's, I'd look real closely at a cracked upper intake.