I have an 88 lx 50 with 220k on the motor that has never been pulled apart.

On my way to work this morning as I shifted into second gear as I applied the gas I had a back fire (pop, pop,pop) and it sounded like it was in the intake. What causes that?

 

It could be a sticky or burned valve.If this was a one time thing then don't worry about it.If it happens more often then a remedy is in order.For a burned valve the only fix is to remove the heads and have a valve job done.You can test for burned valves with a vacuum guage or a compression check.The stuck valve can be cleaned up by using cleaners or top end lubricants added to the oil or fuel.With the mileage you indicated I will lean toward valve seat recession.This is where the valve seats have worn to the point where the valves can no longer seal the combustion chamber.If this is the case,the valve springs are holding the valves against the rocker arms which are pushing on the pushrods and lifters that are constantly riding on the camshaft causing rapid wear on the camshaft lobes.

 

I did a timing check on the car and it was at 6 btc. I was always told that it should be at 12 or 14 btc. so anyway I set the timing and then ran the car up to about 3k rpm and didn't notice any skipping around like some older distributers have.