What cause miss fire cylinder #6

[kakarot]

CEL came back p0171! OK guy really need help on this I have replace 02 sensor(pre cat), replace MAF clean TB , fuel filter and CEL popping same code p0171.
I took out the spark plug check it out and all look fine some are dark but it dry except # 6.
#6 spark plug is wet and black it doesn't smell like oil or antifreeze, could it be a bad fuel injector on cylinder #6.
The engine is idling rough(starting,driving I can feel the engine shake)
I replace with new spark plug same result. I wanted to make sure if it the fuel injector because it cost a lot of $$ or could it also be bad spark plug wires.

Thanks

 

[J-money$$$]

replace plug wires/ plugs first. Then i would try moving the coil packs around and see if the missfire follows a coil pack. If not then you are left with only a couple options. Bad Fuel injector, or a valve issue, or both. A compression test can determine if its a valve issue. If the numbers look good then you can be pretty sure its an injector.

I had a miss fire on number 4 and this is how I went about tracking down the problem. I had bad compression and a failed injector $$$$$

 

[kakarot]

J-money$$$, Thanks for the advice
I'll look into and see what is the issue I'll report back.
when you mean switching the coil pack do I have to moved the spark plug wire with the coil pack as well.

 

[TheDurk]

J-money$$$, Thanks for the advice
I'll look into and see what is the issue I'll report back.
when you mean switching the coil pack do I have to moved the spark plug wire with the coil pack as well.

NO. Leave the wire where it is. Disconnect it from the coil. Remove the bolt holding the coil in. Then do the same with a different coil pack and install it in in the hole you just removed the pack from. Reconnect the plug wire in the same LOCATION (but now on different coil pack). Install the other coil pack in the hole that is now left behind. Reconnect that plug wire. If the misfire changes cylinder, problem is the pack. If the misfire stays at #6, and plugs and wires are new as Jason suggests, problem is likely the #6 injector.

 

[J-money$$$]

Glad you caught that. I gigot to mention that. Don't move the plug wires around. Bad bad

 

[kakarot]

J-money$$$ and TheDurk, Thanks for the great advice I think I have solved the issue keeping my finger cross. Here is what I did I swap the ignition coil #2 with #1 as you advice and I also put in new spark plug wires. The old plug was reading around 7ohm and the new plug wire was reading at 11.17 ohm do you guy think it was the wires that fixed the issue or was it the ignition coil swap. My CEL has not come on yet it usually show up around 63 mile and now it has pass that it's around 80mile. I hope that will solved the CEL p0171.
Question do I need to swap the ignition coil back or is it safe to drive with the swap coil.

 

[Charlee78]

Just a note here, P0171 is System too lean. It is not a misfire, a cylinder not igniting for any reason would give you a system too rich... Just my toughts...

 

[Charlee78]

Have a look herehope this works)

View attachment CI__P0171__P0172_Ex_Ca_.pdf

Maybe you have a misfire if yours is really too lean...

 

[kakarot]

Charlee78, Thanks for the pdf
The guy at autozone did the scan for me and here is what he printed out.

1. low fuel pressure
2. Faulty MAF/VAF sensor
3. Cylinder misfire condition (Note) #6 spark plug was wet when I remove it, it's not antifreeze or oil so my thought was fuel.
4. Large vacuum leak

#2,4 has been check and replaced and was still popping out p0171 so I move on to #3 I swap out the ignition coil as J-money$$$ and TheDurk advice and put in new spark plugs wires the CEL has not come back yet. Keeping my finger cross if it did come back I'll have to do #1.
In the mean time everything is looking good thanks to all those that help.