Diagnosing Engine Intake Backfire - Car Pros Only?

The very first thing I would be doing is making CERTAIN that you've got those leads on the right way. Ok, you've got the firing order, so now you need to find out which way the distributor spins, don't just assume it's clockwise. Take the dizzy cap off and get your friend to turn the engine over, then you'll be sure of it's rotational direction, and you'll be able to put the leads on in the right order.

Then find the timing mark on the crank pulley by rotating the engine over by hand using a breaker bar and a socket on the crank pulley bolt. The mark will be a notch in the pulley, mark it with a white paint marker, or just give it a good scratch with a screwdriver, just to make it a little easier to see. There will be a timing mark on the timing cover that will need to line up with the crank pulley's mark during the test, make sure this is easy to see as well. Some cars have multiple marks on the timing cover to show varying degrees of timing advance, in this case find the correct setting in the manual and put a dab of paint on the correct timing mark.

Connect a timing light to the spark lead on cylinder#1 (the inductive pick-up on the timing light is directional, face the arrow towards the sparkplug-side of the lead), and start the engine. Aim the timing light at the crank pulley and make sure your marks line up. If they don't, loosen off the dizzy bolt and turn the dizzy until they do. Your timing won't be entirely accurate just yet, you should always do the final timing adjustment with the engine at normal operating temperature, with the vacuum advance hose disconnected and plugged, and with all electrical accessories turned off, but this will give you a base mark, and the car should run ok.

Usually backfiring in the inlet is caused by retarded timing, don't jump straight to the timing belt since this is a big job, but after you have checked the simple things, consider the belt as a possibility. Based on what you've told me, I personally think you've got the spark plug leads on the wrong way, but diagnosing things over the internet is a bastard, and it's been ages since I've worked on an old Mazda and I can't remember which way the dizzy is meant to spin.

Good luck with it.

EDIT:

Oh btw, somebody mentioned the MAF meter as a possibility. Don't consider checking it, since a 1985 Mazda 323 doesn't have one :-)

I was glad to see in your additional details that you straightened out the firing order. I knew it would be that when you said that all plug wires were off. Many engines in fact have more than one firing order.

What you're going to have to do about the timing is clean off the timing marker by getting underneath the car. Then get yourself some white nail polish and fill up the notch with the timing mark is. You should be able to see it pretty easily now. I cannot understand why the markings would not be there, so just look a little closer. There's got to be a notch there somewhere.

Other than that, I'm not going to explain how to check ignition timing, just open up a book, they will tell you.

It's pretty doubtful for a timing belt or chain to slip. I'm not saying that it never happens, but it is suspected much more than it is actual. Your belt or chain will have had to been loose beyond the tensioners ability for at least 40,000 miles for it to get that loose to where it may possibly skip. In all of my experience I have only witnessed this one time. It was on a Nissan 200SX that had over 200,000 miles on it with the belt never changed.

Since you say the crankcase ventilation was straight without a valve, there's a good likelihood that the engine has got a lot of carbon deposits built up in the combustion chamber. A situation like that would make any engine run very poorly, so you might want to clean that up with either some seafoam cleaner. A lot of mechanics use ATF. ATF does work excellent, but I can't recommend it because I don't know whether and not it is good for the environment, or rather bad for the environment.

Back to the belt or chain. To answer your question as to what to do to find out whether or not the belt or chain has slipped. You need to either move the timing case cover, or the cover of the timing belt, whatever it be named on that engine. Check the tension on the belt or chain. If there is any tension at all on it, it's highly unlikely that it has skipped. If there is more than three quarters of an inch of play on the loose side of the chain or belt, then I would be suspicious. Skipping usually happens when it is possible by a sudden deceleration from acceleration state. Then suddenly the engine runs profoundly different. Will not idle unless you keep your foot on the accelerator, and is very hard starting. Or, the engine will start and race very high. At least 1500 RPM above normal. When you try to accelerate, it tends to stall out. It's possible, but you don't see it very often.

Many of us were not born with a silver spoon in our mouths and might even be considered poor. You just make sure to get a good education so you can make enough money that these days will only be fond memories. Keep a check on the oil daily. It is best to pull the dipstick before the vehicle is cranked up. This provides a true reading without even needing to wipe the stick. If there is no engine rattle or knock you probably did not do any serious damage. The exhaust leak is a very major concern. -----Carbon Monoxide is a poison. The least worse, prolonged exposure, can result in future major health problems. At the very minimum the oxygen deprived lungs can result in diminished learning ability, because of the lack of oxygen to the brain, before getting to school. The very worse could be death. If you smell exhaust fumes in the vehicle, experience headaches, burning eyes, or seem out of breath you are at risk. However, the smell would be exhaust fumes contaning unburnt fuel. There is a risk that Carbon Monoxide is getting into the vehicle even if there is no smell. Carbon Monoxide is colorless, odorless, and deadly. Rolling the windows down is worse than turning on the A/C or even heater(if cold) because the heated exhaust fumes rise. Rolling the windows down gives it an escape route. Turning on the A/C pressures the cab to a degree and can actually block hotter gas from entering. Your mechanic is not fully up to date on health hazards and the concerns of exhaust leaks. --------------------Please---------have this addressed as soon as possible. Whew!! Aside from this; The "crushed" exhaust is a result of the engine, or part of it, making contact with the exhaust and usually pushing it into the body or frame. "If" the exhaust is still making contact with any part of the body or frame there will be vibration. It sounds to me that there may still be an engine mount broke. There are at least 3 and usually 4 mounts. One on the front of the engine, one on the rear at the transmission, one on the side towards the radiator, and one on the side by the cab. A mount can be bad and not look "broke" and can be checked by usuing a bar underneath to pry on the engine, a jack, and also a more simple method that works. Have someone stand by the side of the car looking under the hood. Apply the emergency brake(and foot on the brake) and put the vehicle in gear. If a mount is bad the motor will make a lot of movement but then shift to reverse. Now there may be very noticable engine movement. Also if a transmission mount is bad it can put the shifter linkage in a bind. The sand sound is probably air escaping the hole in the exhaust. The shift problem could be a seperate problem indicating the transmission filter needs service or because the vehicle is not running properly. Your number one concern is the exhaust and your health. Walking healthy is better than riding sick. There are a number of ways to repair an exhaust leak. There are repair kits at the parts house but the best is to have the exhaust repaired by ethyne(acetylene) welding or brazing. I have used a torch and a coat hanger with great success. Just because the vehicle speaks with a foreign language does not mean this will not work. Good luck, be healthy, live longer.

You said you have a manual, or at least that is the way I understood it perhaps you were only reading from the internet if you were then first purchase a manual for the car. Then go to a parts store and they will rent you a timing light usually giving you back your deposit when you return the tool. Look in the manual for your particular engine and follow timing procedures, it does sound as though the timing is out a couple of teeth probably why it was parked in the first place. As far as your empty tank being full of fresh fuel, if you didn't clean the tank out then because it was empty it was able to rust in a much wider area however the fuel filter, if it was also replaced, should stop most of the trash it's the plugging up that you will have to worry about. The firing order as well as rotation you will find in the manual as well.

Wow! Most do not give near enough information but sometimes too much and a series of events can be hard to follow. I assume "dizzy" is the distributor and or cap?

--You asked for it so I will oblige you some.

----Many things can cause an engine to backfire and poor/bad fuel, or lack of fuel/too much fuel, vacuum leaks, bad sensors, and timing, are some.

--1)- You must ensure the basics. The vehicle was sitting a long time. It was on "empty so you put new fuel in it so you assume, "there's no stale fuel running in it.". If you do not know it ran totally out of fuel this could be a very false assumption.

--A vehicle on empty, especially if it has a low fuel light, can have up to a gallon of fuel. If the fuel was bad(past stale), evidenced by a strong bad fuel smell, there was water in what fuel was left, or both, you could still have problems. even if the vehicle was filled with new fuel it would be what--10 or so gallons? One gallon of bad fuel would be detrimental. If only a few gallons were put in it then it would be worse.

--2)- You monkeyed with the P.V.C and oil was sucked into the air filter. There is a possibility that the mass air flow meter was contaminated.

--I could write several pages on cause and effect but will keep it relatively simple. The M.A.F. measures the air intake and with other sensors is used to adjust air intake, fuel, and timing, to ensure near 14.7:1 air/fuel ratio. This ratio is referred to as stoichiometric or fuel stoichiometry. This varies a little on some newer emission controlled vehicles. At sea level and the proper temperature all fuel will(theoretically) burn with 14.7 parts air and 1 part fuel.

--3)- If the M.A.F. sensor is weighted down with oil it will cause a back fire. Normally this would cause a sever lack of air with too much fuel(flooding) but on newer vehicles the sensors will adjust for this and cut the injector firing time down to compensate and can cause lean misfire..

--4)- Clogged fuel filter(lack of fuel). Pull it off and at least inspect. This is a maintenance item so should be replaced.

--5)- A bad vacuum leak(lean again) and very important

--Before you can go into the theory of mechanical engineering you have to begin with the basics. All of the above(also timing), can cause a lean misfire which would cause a backfire. Check these out, be ----100% ----certain, and if you still have a problem repost concerning the timing.

--Is there a check/service engine soon light on? This would mean a code is stored and can futher complicate things.

--I am no longer a technician(mechanic with speciality degrees) so I hope my lack of current qualifications does not hinder my ideas. In my defense I was A.S.E. certified in many areas including factory on-board computer diagnostics and repair training.

--I feel that my studies in stoichiometry placed me at the head of the class as obtainng this on a vehicle can either gain the ultimate fuel economy and performace or the ultimate power for racing.

The easiest way to CHECK timing on a 4 cylinder is to pull the valve cover (pull the plugs first) then put a long socket extension in cylinder 1's plug hole (so it sticks out; spin the crank pulley by hand until the extension is at the apex of travel (the highest travel point) that's TDC (top dead center). At this point the arrow/marking on your camshaft(s) should be completely visible and in it's original position (which is parallel to the head (the long portion). If it's not the timing needs to be adjusted so that TDC has the cam(s) marking parallel to the head. Give or take a degree or two SHOULDN'T be a big deal.

with out much reading into the problem the car has been siting for some time and its 1985 Model year if me mere service me right it has a timing belt and overhead cams right and left the belt has slip ed and is out of time to fix you will need to replace the belt and reset the timing marks on the cams and the crank shaft hope that your up to the job if not get tech manual to help you out for it is a long proses and for my SLF with 30 years and all the tools takes me a good 8 hr to do the job right PS you will also whant to check the belt tensaner and posable whant to change it as wall at the same time along with some heater hoses in the near by area water colant tubemay be getting rusted out and the colant may also need to be replaced as wall

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If you have no knocking internally it just sounds like you need a major tune up. If you cut the entire exhaust system off, the car would still idle smoothly. Leaky valve seals will foul out plugs, but unless oil is just pouring in, it does take time for it to foul out plugs.

Backfire Through Intake

Have a close look at your manifold.is it in two parts,is the inlet and exhaust pipes bolted together and has a thin plate between them ,that is called the hot spot plate that warms the fuel as it enters the engine,when this plate gets corroded or burned through and creates a small pin hole in it,that allows the hot exhaust gasses through into the inlet and you get bang bang if you have that type of manifolds