I bought my boy a 2000 as a learning project.We bought a short block and put it in (wish I would have seen the Seafoam thread!). It only had about 103000 on it but it had a blown head gasket and serious water scale buildup in the head. We cleaned the head and valves up and it ran great after firing it up. It still runs ok, but engine light is on and it throws codes related to cat converter. We replaced both O2 sensors, have a new cat converter on the way.
Problem is a pretty scary knock down near the bottom of the engine. I am hoping this is not a rod bearing or other major failure. Up top it doesn't sound bad, under the car on a jackstand is a bit clanky at the rev rate of the engine.
Worried about the knock we did run a partial can of an engine decarbonizer from OReillys in the oil and gas tank (per instructions). We ran it 60 miles and then had an oil change. Still knocks pretty bad. We have not yet filled it and it is 87 regular octane unleaded gas.
So, thoughts? How do we tell if there is a rod or crank bearing problem. We only have about 2000 miles or less on the short block. We tested the advance solenoid and it seems to work well and be pretty balanced gaps in its 2 stroke positions.
Suggestions? Would the Cat throw off the whole operating mode of the engine enough to damage it or cause this noise temporarily until replaced?
By the way, to get the emission inspection past we soaked the cat in a mild acid bath for about 12 hours. It ran with no light for about a week and then the cat code came back.
Dare we drive it more? I'd like to run it in and get premium grade gas.