CAMS, LIFTERS AND CHAINS
Sounds like a rock band. Unfortunately it’s not. It’s a list of three common faults with the Jeep 3.6 petrol engine which is fitted to the Wranglers and the WK2 Grand Cherokees.
All of these issues are common, however they do not always fault at the same time and they don’t all give the same symptoms. We have done several of these on a variety of vehicles and advise to always do these as a group however the replacement for all of the afore mentioned parts can be a very costly repair.
Below is a list and some images of the faults and the symptoms you may get with them.
LIFTERS & ROCKERS: The only real symptom you will have with this is a very loud ticking noise from the top end of the engine. If left for to long this can cause the camshaft to wear out prematurely (which is the next item on our list) and/or develop a misfire. The noise is caused by either a failed hydraulic lifter or the roller component to the rocker seizing up. Either way always replace the lifters and the rockers together.
CAMSHAFTS: The case hardening is known to wear out on the camshafts. In our experience the exhaust camshaft on the passenger side (hight hand drive vehicles) is the first to develop this problem. This is often caused by the above mentioned lifters and rockers fault being left to long unattended. Once the case hardening is worn out, the lobe on the cam shaft very quickly wears down. This creates a loud ticking noise and prevents the rocker arm from pivoting enough to open the valve. The result is a Misfire. This can be hard to diagnose and compression will still be good (the valve doesn’t open at all) obviously spark and fuel will be ok. It’s not uncommon for mechanics to replace injectors, plugs and coils (all of which are also common for giving trouble) only to find the misfire is still there. If this is occurring, remove the valve cover and inspect the camshaft lobes for wear.
TIMING CHAINS: The timing chain set up on these engines are also known for stretching. When this happens the vehicle will normally log fault codes for cam and crank shaft correlation however they are also known for logging codes relating to engine torque performance. Of note. The cams and the lifters and rockers can all be replaced without the removal of the timing chains, provided to correct specialist tools are available to lock the cam gears in place.