Miss firing on #7 rough idling and exahust smell in car

[DerickAB72]

So for the past week my car has been idling really rough when cold in the morning. After the care warms up it calms down but still has a rough idle. I ran the codes and I got a 171 and another code (I don't have that information with me since I'm at work right now). Anyway...... one the cylinders came back as a misfire so I changed all the plugs and the coil on #7. The car is still having the same issue and it also read that the car was running lean. Also you can smell the exhaust in the car (I do need to change the cabin filter) that wasn't there prior to this idling issue. I started just replacing the sensors one by one but that is getting costly. can anyone help me out in diagnosing this issue. I just need it to get me through the winter and I may be selling it. Just brought a house so I don't have the money to buy a truck just yet.

Thanks in advance.........

 

[joegr]

If you really want some help, you are going to have to give some information.

Exactly which OBDII codes are you getting. The five character codes, not the "meaning."
What year LS do you have. How many miles.
I assume the V8 since the V6 doesn't have a #7.
What all has been done to it before this problem? (Have the timing chain tensioners been replaced? ...)
What have you done trying to fix this. What specific parts have been replaced?
What spark plugs did you use? Did you set all the gaps to 1.0mm?
What brand coil did you use? (First rule of the LS, don't replace just one coil, replace them all.)
Was there any oil in the plug wells. Was there any sign that water had been in any of the plug wells.
Did you check for intake leaks?
Do you have an aftermarket air filter / intake?

 

[stumpy]

also try spraying the down and around the plenum and intake with throttle body cleaner...listen for RPM changes. this will tell you if there is a bad air leak somewhere.