A friend of mine has purchased a 2005 GMC Envoy XUV for his son. He got a pretty good deal on it but it does run a little rough. It also makes a lot of noise while driving. There’s a clanking sound coming from the engine bay and the check engine light is on. Now that the truck is in front of my house, it’s time to troubleshoot! That’s what I’ve been doing instead of working on the Monte.
First off, the check engine light. I plugged my code reader into the OBD2 port and read the codes. It was a P0300 Random misfire code. Unfortunately this does not isolate an individual cylinder but signifies that multiple cylinders are being affected by the problem. I pulled all the plugs to see if I could find anything abnormal but I could not. Other than being worn out they looked normal. I then decided to do a tune up on the truck to see if that would solve the problem, it did not.
I was then forced to purchase a spark tester to determine which cylinder was causing the misfire code. I went through each cylinder and eventually found that the coil pack on cylinder 3 was not firing at all. I ordered the new coil pack and replaced it. To replace it, just follow the instructions here that show how to replace the spark plugs; just don’t take out the plugs.
The next thing I took a look at is the rattle in the front. This appears to be a combination of the misfire problem making the engine run really rough and the tensioner pulley being worn out. If I pull up on the tensioner pulley, the noise pretty much stops. The tensioner pulley will need to be replaced.
Replacing the tensioner pulley in a GMC Envoy was easy as pie. This is a very easy job that probably can be performed by anyone that can turn a wrench. Take a 3/8 inch drive ratchet and place it in the end of the pulley, there is a slot that the ratchet will fit right into. This will give you some leverage to loosen the serpentine belt and remove the belt from the pulleys.
Old Tensioner Pulley, You Can See The One Bolt Holding It In
Loosen The Tensioner Pulley With A Ratchet
Next, just find the correct socket to fit on the bolt and use a breaker bar to loosen the bolt that holds the pulley in place. After the bolt is removed, the tensioner will come out. Installation is the exact opposite.
New Tensioner Pulley Installed
There is more issues with this truck, there is a bad grinding noise when driving down the road and I think it is a wheel bearing. The below video shows the troubleshooting procedure to determine if the wheel bearings are in fact bad. The front driver’s side wheel bearing is in really bad shape. I’m surprised that the wheel hasn’t fallen off! You can see the replacement procedure in this post.
The rear wheel bearings were also causing a problem and I checked them as well. I found that the passenger side rear wheel bearing was bad. I decided to replace both of the rear wheel bearings since there was a lot of work involved to take the bad one out. You can check out this post for the procedure.
The end result of this project ends up being unfortunate. After replacing all 4 wheel bearings, doing a tune up, replacing a coil pack, changing out the Camshaft Position Acutator Solenoid, and replacing the tensioner pulley, the engine is still recording a random misfire code. I’ve checked all the common culprits for this vehicle that cause the code, I tightened the plastic intake manifold, made sure all the coil packs were firing, checked the fuel pressure, and cleaned the throttle body to make sure all the simple things were taken care of. Hooking up a vacuum gauge to the motor is revealing a possible leaky or sticky valve. This is also a common issue with the Envoy and typically requires replacing the head. I recommended to him to get a second opinion, since I am not a trained professional and that a leak down test would confirm if that was the case. It would also be helpful if we had a more technical computer to actually read the codes that are being triggered.