1985 cj7 jeep 258 engine is noisy on idle. rattles constantly , rebuilt engine twice and prob won't go away.
This is kind of hard to judge without hearing it. Lets say the noise is the pellets in the Catalytic converter that some types of automakers used, with low flow at idle, the loose pellets can bounce around until the flow increases and pins them to the insides of the Catalytics.
However, if you rebuilt the motor you would know some mechanical stuff. I can move on to more possibilities.
Oil pressure starvation can make the pushrods rattle in the rocker arms. The engine oil pressure will cushion the critical area between the rocker arm and the pushrod seat.
On the rebuilds, have you worked on the heads? Like valve spring tension and pushrod clearance? I have had engines that would idle perfect until accelerated and return to idle clanging and missing. The valve springs were shot. Then I have had some GM motors that had hydraulic lifters yet the pushrods were different lengths and that is how the pushrod clearance was made; by changing individual pushrods to get the correct clearance.
This is something that can occur when the valve seats are cut. The valve stem can ride up into the head slightly when the seats are cut.
Now you may have replaced the camshaft or the lifters or not. But it is recommended that each lifter is paired with a camshaft lobe. If you mixed the lifters into different positions, you may have distortions that are resulting in noisy clearance problems. For that matter, camshaft bearings may be loose.
The Jeep and American Motors cars used a 232 CID engine too. Can't say what components were different but you may have mixed parts.
Now some models used a Rattle or knock sensor, and in the old days, you could get a rattle from weak distributor springs in the breaker plate. The mechanical advance would throw out too fast.
I am curious. Would like to know what you found.
Oct 31, 2012 |
Cars & Trucks