can any one till me what do I need to check?When am driving and am ready to go to the next gear as soon as I let off the gas I get a pop.pop sound
1973 1.7

Carbs or FI ?

A tight int valve could cause it, an air leak causing it to run lean, too much fuel.

A few things to check out first to rule them out.

find and fix your exhaust leak.

Rich said it right. Exhaust leak.

It is funny, I am having the same problem right now. My car was tuned in Atlanta with no problems, when it got to florida, it started backfiring. I spoke to Sean at Auto Atlanta on Fri, and he told me that if it is backfiring out of the muffler, it is running to rich, to much gas. If it is backfiring back inside the engine, like a pop, it is running to lean, not enough gas. He thinks in my case it has something to do with the elevation change. I will be tinkering with mine today. This is of couse assuming that you do not have an exhaust leak. Thak must be fixed first, if you have one.

James

yes its fi/I will check for a exhaust leak

An easy way to check for a leak is to use a rag so your hand doesn't get dirty, and if you have a single outlet exh, just cover it up, if the exh is sealed, it will run for a few seconds then die, if it's not sealed it will continue to run since the exh is getting out. It's like the old potato trick, that people useta do, stuff a potato in the tail pipe, and the car won't even start...