Cylinder 6 Misfire, Po3o6 Code?

[lltrevino]

Engine Performance problem

1998 GMC Sierra V8 Four Wheel Drive Automatic 130000 miles

 

I am @ my wits end. I have a dead hole in my 5.0 engine. I pull a p0306,cylinder 6 ,misfire. I have changed the cap,rotor and plugs, spider assembly, upper and lower intake gaskets, the cmp sensor, the Bank 1 sensor 2 O2 sensor, the bank 2 sensor 1 sensor, ECM, and a new fuel pump/module is on the way.

I have done some limited scans, and bank 2 fuel trims are rich, still, even after gasket change on lower intake. I did find #2 intake runner gasket was bad, along with front coolant port. I have done a vacuum test around 13# steady. Did compression test and running compression test, found nothing out of the ordinary. However fuel pressure immediately drops, when fuel pump stops running with key on engine off. I have traced the pump to be leaking(pinched both fuel lines, only than does pressure hold). Now i installed pump, it holds fuel pressure fine, but still a cylinder 6 misfire. However unsure why is only picking on bank 2 cylinder 6 especially. I pulled banks 2 plugs. all are black, EXCEPT CYLINDER 6???? Cylinder 6 is still whitish, with minimal black. This truck only has 1 coil, for all 8 cylinders, why is 6 a problem, when static, and running compression is still in range with all other cylinders?

 

This is a friend's truck, i did also find MAF sensor in backwards, I did clean it, install correctly. However also getting 8.4 g/s on scans. I am going nuts here, what am i overlooking??? here is a freeze frame

[bill190]

Did you replace the spark plug wires?

 

Try these...

 

Fuel Injection Service, Not Just Cleaning...

http://www.asashop.org/autoinc/june98/techtotech.htm

 

Misfires...

http://www.random-misfire.com

 

Then if all else fails, get a GM factory Fuel and Emissions Service Manual for your year/model vehicle and follow the troubleshooting testing charts in that. Might want to get the full service manual set - 4 books.

[Operation Mindcrime]

Did you try an injector balance test??? Check pin grip(electrical connection at fuel meter body) on the injectors??? Is the injector pin terminal broken or bent from disconnecting/connecting the injector harness??? Open #6 plug wire?? I'd start with the above.

[lltrevino]

wire test on great, new wires were installed with a tune up to first correct issue. I have put a noid light on to check for injector firing, it is fine. owner had advised me to put a new ecm in(against my judgement), that was not a problem. last night i pulled plugs on bank 2. cylinder 6 plug indicated correct plug reading, while cylinder 2,4,8 all were dripping gas. this leaves me to believe, somehow, cylinder 6 is sucking LOTS OF AIR, while all the other plugs are all sucking normal air. what is going on?????

[Draenor]

You say #6 is whitish? Like an ash on it? White ash is a contamination, either by coolant or possibly oil. You may have to reinstall your intake gasket or you might have to pull the head and inspect the head gasket.

 

When you replaced the intake gasket, did you check for warpage?

 

*just thought of another*

The cylinder temps could be too high. Are you using the correct heat range plugs?

[lltrevino]

Out of the clear blue today, the truck just magically cleared up??????? no clue how or why??? talk about confusion, could there be a sticky valve or lifter?

[lltrevino]

Thanks for the ideas though, and keep 'em coming.

[lltrevino]

You say #6 is whitish? Like an ash on it? White ash is a contamination, either by coolant or possibly oil. You may have to reinstall your intake gasket or you might have to pull the head and inspect the head gasket.

 

When you replaced the intake gasket, did you check for warpage?

 

*just thought of another*

The cylinder temps could be too high. Are you using the correct heat range plugs?

 

 

I meant 6 was white, due to nothing evening appear to be happening in the cylinder. It was white as no fuel entering, or the plug appearing to be ALMOST new like. I did put some fuel additive, it did have some small red spots, which I believe was the fuel additive. However all the 3 other cylinders in the bank, were excessively rich appearing.