There is a gasket installed between the cylinder head flanges and the intake manifold. If its tightness is compromised, the engine runs unevenly ("troit"). If the malfunction cannot be eliminated by tightening the intake manifold mount, replace the gasket.
1. Remove the cylinder head assembly with the intake manifold (see "Replacing the cylinder head gasket").
2. Remove the bolts securing the intake pipe to the cylinder head.
NOTE: This is the location of the intake manifold mounting bolts to the cylinder head.
3. Remove the intake pipe.
4. Remove the gasket from the grooves of the intake pipe.
5. Clean the intake manifold grooves and install a new gasket in them.
6. Install the intake manifold in the reverse order of removal. Tighten the intake manifold mounting bolts evenly crosswise to the torque specified in Appendix 1.