Today I took my new to me stock 82 4x4 5spd offroading. It runs very well and smooth, and continues to do so, however…
I was heading down a long fairly steep hill using engine braking to maintain speed. All of a sudden there was a very loud pop and a second later another one. I stopped and saw that there was now an exhaust leak in the muffler. A few minutes later the same thing happened again, but this time it completely tore open my muffler.
My theory is that due to the higher engine speed and the throttle plate closed, the engine pushed a decent amount of unburned gas into the exhaust where it then ignited. I also believe that the air pump helped this process by flooding the exhaust with oxygen.
Any thoughts on how this can be avoided? My thinking is that I should take the air pump belt off when offroading to avoid this. The engine continues to run fine, and actually improved on pickup due to the now unrestricted exhaust.