What makes a vehicle backfire?

I've been experiencing some odd engine problems in my Tracker lately: the main oddity is backfiring when coasting in gear to slow down. It also has a somewhat unsteady idle, and runs pretty rough... what sort of things cause this?

EDIT: 92 Tracker engine; 62k miles; 5k on rebuilt head

Timing. look at that 1st.

Ahhh it'll be okay My tracker did that when it had 50k on it. It's just a lack of exhoust. Hey man also im looking for a good running track/kick. do you still have that one? if so do you think you might get off it? Hey maby i'll post a movie of the sammy shooting flames. But other than that dont worry

Hrm... valve clearances and everything? Off to the garage, I am.

Zookiemike: I do have that Tracker, unfortunately there are still several things that I need to fix on it... right now it seems to be running great, but has a small coolant leak, and I have to fabricate some new gastank mounts, because when I dropped the tank, 2 of the mounts disintegrated.

I still don't know if I'm selling it or not, yet :-/

Rich/unburned fuel causes backfire at decel and coasting,
look at plugs/timing, fuel PSI, Cat convertor, Wires and
O2 Sensor, a weak/old coil for the fix on this, mine idles
a little rough too, I have been thinking about a high output
coil to see if it solves the problem

Wild

  I've been having the exact same problem on my '87 Samurai. Backfiring in the exhaust pipe on decel. I've heard that you can adjust the mixture on some carbs to fix this problem. I haven't tried it with my Sammy yet. Has anyone tried to fix this problem using the mixture screw?

Rich/unburned fuel causes backfire at decel and coasting,
look at plugs/timing, fuel PSI, Cat convertor, Wires and
O2 Sensor, a weak/old coil for the fix on this, mine idles
a little rough too, I have been thinking about a high output
coil to see if it solves the problem

Wild

I dicked around with the distributor adjustment for a few minutes yesterday to no avail, so I just set it back to where it was. My thoughts were on wires next, but the coil suggestion seems like a good idea. Anyone have a link to a place that has specs/sells that MSD coil that have been posted here before?

Also, how hard is it to wire in a different coil? Are there just a few wires, or is there a lot of splicing and other stuff to do to get an aftermarket coil to work?

I think I'll pick up some new wires... I am doubting it's the cap or rotor, as they were replaced about 4500 miles ago.

Well I don't know about the wires, I had
some hesitation at freeway cruise and found
the wires to be going bad, funny thing is it
idled just fine, but it felt like surging on the
freeway, O2 would tell the computer to lean
out the mix, so I would look there too, the coil
I think was about 45-50 bucks    but I'm going
to look at the wrecking yard for a replacement,
the coil is an easy 2 wire swap, 3 if you count
the high voltage lead

Wild

Hrm... my idle isn't horribly rough (well wasn't when I left the distrib alone)... just fluctuates 100 rpm or so at a time. I don't remember it doing that. :-/

The real problem: It drives normal in 1st through 3rd, but as soon as you hit 4th, absolutely ball-less. If I'm not coasting it's constantly decelerating.

I'll have to go out and check all that stuff :-/

Set (or have it set) the timing at 10* to 12*
advanced, this should run the best

Wild

I got new plug wires, fixed the problem

Now to acquire a timing light...