I performed a tune up on the 2005 GMC Envoy that I was trying to fix. It had a misfire code so I decided to replace the spark plugs and the Air Filter. That is pretty much a tune up on this car since there is no fuel filter. I have read some posts and other forums on the internet that states that there is a fuel filter, but I was unable to locate it, even after following the lines all the way to the fuel rail….
The first part of the tune up is replacing the air filter. You have to remove the bar that it is mounted across the air box in order to access the air box and move it out of the way. It is easy to remove, just unbolt the two ½ inch bolts that are holding it on, and then remove it. The next step is to unscrew the three Phillips head screws that hold the air box in place. When they have been removed, the air box will just lift out of the way. You may need to finagle it a little to get it to come off, but it will come off pretty easily. Now the air filter will be visible, you should be able to lift it up and slide it off of the plastic tube. Then just replace it with the new one and put it all back together.
Bar Over Air Box
Old Air Filter
New Air Filter
Now for the spark plugs, you will need to remove the plastic box over the valve cover in order to be able to replace them. First, you will have to take the clamps off of the plastic box and off the throttle body. Once you move the plastic hose away from the plastic box, you will be able to access the two bolts that are holding it in place. Once these bolts are removed, you will be able to slide the box off of the throttle body to expose the coil packs.
Left Side Clamp
Throttle Body Clamp
Move The Plastic Air Hose Away
Remove The Two Air Box Bolts
Remove the electrical connectors from the coil packs. To do this, you will have to lift the grey locking part up to allow the release mechanism to be depressed. I had to spread the edges apart on the locking mechanism to get it to release. Then just push the black release button and pull it off the coil pack.
Spread The Edges Of The Grey Locking Clip
Press The Release Tab
Remove The Connector From The Coil Pack
Next you can loosen the 10mm bolt that is holding the coil pack in place. Once this is loose, you will be able to pull straight up and remove the coil pack off of the spark plug.
Loosen The 10mm Bolt
Grab Both Sides Of The Coil Pack And Pull Up
Pull The Coil Pack Out Of The Hole
Once the coil pack is removed, use a 5/8 inch spark plug socket to remove the spark plug. I put a 6 inch extension on the end of the ratchet to get the socket down into the hole. For the one in the back, I needed to put the extension and socket into the hole and then attach the ratchet to it. The other ones were pretty easy to get to.
When I put the new spark plugs in I put them into the socket and dropped the socket into the hole. I then hand tightened it until I could no longer turn it. At this point I would connect the ratchet and turn it another ¼ turn, depending on what kind of resistance that I encountered when I connected the ratchet. If it turned very easily, I would tighten it until it was no longer easy and then do the ¼ turn.
Drop The Spark Plug Into The Hole
Now the rest of the installation is the exact opposite of the removal. Put the coil pack back on, tighten the 10mm bolt, and replace the plastic air box. When you put the air box back on, make sure that you remember to connect the pcv hose properly. Tighten all the clamps and start it up to make sure all is well.