We have a 1986 Ford Ranger and it started knocking. We changed the oil, oil filter and all 8 lifters. This DID NOT fix the problem. Previously, it was blowing smoke and you had to keep foot on the gas to keep it running at a stop. We cleaned up the spark plugs and nnow they are working fine and it was fine for about 2 days. Any ideas??

What color was the smoke? Has it ever overheated? What's the mileage?

Remove the spark plugs and check each cylinder's compression. Record the results. Check dry and wet.

Well we took it apart last night and its pistons are shot. I think we are going to rebuild. That's all we can see. Thanks

Shouldn't be too bad on a Ranger. I'd use a FelPro gasket set, new pistons and rings, and likely replace the journal bearings.