malibu rough idle  

Group: alt.autos.chevrolet.malibu Date: Sun, Oct 26, 2003, 7:01pm
(CST-2) From: dgorzynski@sernas.com (derek)
Need help!!
Had a coolant leak (famous 3.1L GM – 96,000 km) from lower intake
manifold gasket. I replaced that gasket and both head gaskets at the
same time. When I put everything together, engine misfire on #6
cylinder. Heads are OK, valves are OK.(checked by professional shop)
  Problem is when exhaust valve rocker is tightened properly there
is misfire and loss of compression in that cylinder. If I loosen up the
rocker it works fine but it starts to make clicking sound after a while.
I changed lifter and pushrod – same thing. Where is the problem
– do I need some sort of a shims between the rocker and pedestal
to get the correct preload on the valve. Could it be valve spring???

Valve spring would be my guess....I had a head sent off last week
..Came back with no problems...But i knew there was on so i took apart
the head my self ...Found the valves one the #1 cylinder pitted and
loose ...Sent it back  to have then replace the valves and seals ...This
too was a professional shop.....Eighter change the springs or get a
second opinion on the head...
Steve C

May be you  switched the  exhaust and intake push rods? The exhaust push
rod is slightly longer than the intake pr.

You probably mixed pushrods and rockers each other. So it makes an (or more) intake or exhaust valve leaking. That is why you tighten the bolt it leaks, loose the bolt it seals. Because the clearance is not adjustable for your engine, the manufactory only recommends mechanic keep everything order for installation in its original position and use proper specifications to tighten them. Once you mixed them, some pushrod can't seat on the lifter properly or little longer than its oringinal, which always pushes the valve rod result in valve leaking. Although it is very little, it still affects idle spead. After you changed the return spring or run in high rpm, it might make valve on seat.

You probably mixed pushrods and rockers each other. So it makes an (or more) intake or exhaust valve leaking. That is why you tighten the bolt it leaks, loose the bolt it seals. Because the clearance is not adjustable for your engine, the manufactory only recommends mechanic keep everything order for installation in its original position and use proper specifications to tighten them. Once you mixed them, some pushrod can't seat on the lifter properly or little longer than its oringinal, which always pushes the valve rod result in valve leaking. Although it is very little, it still affects idle spead. After you changed the return spring or run in high rpm, it might make valve on seat.

You probably mixed pushrods and rockers each other. So it makes an (or more) intake or exhaust valve leaking. That is why you tighten the bolt it leaks, loose the bolt it seals. Because the clearance is not adjustable for your engine, the manufactory only recommends mechanic keep everything order for installation in its original position and use proper specifications to tighten them. Once you mixed them, some pushrod can't seat on the lifter properly or little longer than its oringinal, which always pushes the valve rod result in valve leaking. Although it is very little, it still affects idle spead. After you changed the return spring or run in high rpm, it might make valve on seat.

You probably mixed pushrods and rockers each other. So it makes an (or more) intake or exhaust valve leaking. That is why you tighten the bolt it leaks, loose the bolt it seals. Because the clearance is not adjustable for your engine, the manufactory only recommends mechanic keep everything order for installation in its original position and use proper specifications to tighten them. Once you mixed them, some pushrod can't seat on the lifter properly or little longer than its oringinal, which always pushes the valve rod result in valve leaking. Although it is very little, it still affects idle spead. After you changed the return spring or run in high rpm, it might make valve on seat.