Exhaust Valve Stick Tests
Vacuum Diagnosis1. Attach a non-dampened vacuum gauge to plenum chamber and observe needle. The needle should hold steady at approximately 1 bar(15 lbs). vacuum. If the needle is fluctuating there is most likely a valve stick problem.
Physical Inspection - Valve Stick
Vacuum diagnosis will not always identify a sticky valve. If you are sure that all other causes of misfire have been explored and repaired, the next step in diagnosis is to physically check for a sticky valve. Use the following procedure to confirm a sticking valve.
1. Remove the valve cover and rocker shaft assembly on the suspected cylinder bank, making sure the rocker shaft mounting bolts are loosened uniformly to prevent rocker shaft damage.
2. Rotate engine to TDC on the P-code identified problem cylinder.
Place a suitable tie-wrap around the top of the valve stem to prevent the valve from falling into the cylinder.
3. Using a finger type valve spring compressor, such as KD3271, remove the valve spring keepers, spring retainer, and valve spring. DO NOT REMOVE THE VALVE STEM SEAL. This helps retain the valve in place.
4. Open and close the suspected valve while rotating the valve at 90 degree intervals. If resistance is felt in opening or closing the valve, that valve is confirmed to be sticking. If no sticking is apparent, check all other exhaust valves on the same bank in the same manner.
When head is installed, new bolts must always be used.
5. When a sticking exhaust valve(s) has been confirmed, replace all exhaust valves with ERR7027. Relap each intake and exhaust valve using a suitable valve grinding compound. Be sure to remove all traces of the grinding compound prior to reassembly. Reassemble using new valve stem seals.
6. Refer to workshop manual for disassembly and assembly instructions.
NOTE:
To assist in the process of resolving valve stick induced misfire, Land Rover has launched a cylinder head program to minimize the length of time that the car is held from the customer. Each dealer is sent a small number of complete cylinder head assemblies fitted with the latest carbon break valves. The heads are to be used only to repair valve stick related misfire problems. Allocation of head sets was carried out by LRNA, taking into account each retailer's historical incidence of valve stick related misfire. On customer complaint of MIL illumination and diagnosis indicating valve stick and for more details on valve stick replacement head/valve handling procedure, the steps outlined in section 1-07 of the OPERATION PRIDE manual should be followed in order to allow completion of a valve stick induced misfire repair in one day whenever possible.
Retest After Repair
1. Clear any codes that may have been stored in TestBook, and perform Drive Cycle C. (See Service Bulletin W-96-007)
2. Recheck with TestBook for any newly stored codes
3. If codes were stored, follow appropriate diagnostic procedures.