73dart

Well to start off, I am new to mustangs. But definitely not new to cars.

I have a 1979 mustang that I just got. 5.0L automatic. It was actually a barn find and had been sitting since at least 2000 and probably even before that.

So it all started I dropped the tank to clean it. Well I needed a new in tank fuel filter but had a hard time finding one. So i left it out, but added 2 other in line fuel filters. Plut there is a filter built into the outside of the carb. So total of 3 filters.
It ran pretty good but you could tell it was lacking power and wasnt running to its full potential.

So I went ahead and switched the plugs, wires, distributor cap, and rotor. I honestly have no clue how the car was running before I switched them, because the plugs were in really bad shape. 2 of the 8 couldnt even have been firing as much black crud was on them. It looked like bubble gum wrapped around the plugs are how bad they were. And one wire was melted almost clear in two.

So this is when my problems starts, After I switched all that out.
It will run great. But whenever you put it in gear and take off, it will backfire thru the carb (pop, pop, pop) over and over. If you rev the motor in park or nuetral it will only do it once every couple of minutes. Sometimes it will pour black smoke out of the exhaust.

I have thought about a lot of different things, but unsure what it is.
1) could it be running rich where i left the in tank fuel filter off?
2) could it be something like a lifter, push rod, cam lobe or something else broke and not letting valve open causing to backfire?
3) could it be the smog pump and that whole set up?
4) vacuum leak somewhere?
5) something else i havent thought of.

So whats your guys ideas on this? Im open for opinions on what to try because im kinda lost right now on what to do.

mattdel

Possible timing chain issue creating your backfire, too loose. Might be a sticky valve too.
Possible carb issue creating the smoke, jets stuck partially open. Might even be responsible for the backfire if it leaks enough.

I wouldn't have even attempted to run the car without rebuilding the carb. Gasoline does some nasty stuff when its been sitting.

73dart

Thanks for the quick reply!

That was a stupid mistake on my part to not rebuild it.

But I didnt feel like running all the numbers and such to figure out what carb it has on it. The motor has been swapped I think and im not sure what its out of.

dawson1112

12+ years is a long time for an engine to just sit there. The valve train is probly so gummed up from sitting that its just not functioning very well. I would pull the valve covers and check the rockers and springs clean it all out. Check the springs to be sure you dont have a broken valve spring .
You could possibly run it with some fresh oil and may add some kind of detergent like seafoam to the oil. Just keep an eye on the oil pressure.
You can check the timing chain to see if it is worn by using a timing light and watching to see if the timing is holding in place and advancing smooth upon raising the rpms. If the timing mark is boucing around while idleing or raising the rpm its a sure sign the timing chain or gears are done for. The carb for sure needs to be rebuilt and cleaned out, or better yet replaced.

94redGTConv

I'm sorry man, don't mean to hack your thread, but I just bought a 94 Mustang Gt 5 Speed, I've had an 01 gt before, so I'm not that dumb on stangs, well I figured I'd do normal tune up so I changed the oil and put full synthetic stp filter, new plugs and gapped them to 50 I think but not new wires, coolant looked good and I cleaned my maf, tps and all electronics got a new serpentine and that's about it for mechanical stuff and its just hitting temperatures of 40ish and I when I first leave to go to school it wants to bog like hell until it warm on the thermastat, any ideas? its probably normal but my other stang didnt seem like this, sorry btw for not making my own thread but couldn't figure out how to plus I'm on my phone, does anyone know how to put the window part of a convertible top in for a 94? or could redirect me? thanks guys!


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