slight popping and backfiring

65fastback2+2 · Apr 15, 2004

It doesnt do it at idle, but when im cruising. It does this slight pop quite often. My dad said it is cuz the timing is off, and if it is when do I rotate the distributor clockwise or counterclockwise to fix it???

MustangPaul · Apr 15, 2004

turn it clockwise--towards the thermostat housing. Do it a bit at a time and see what happens.

If you have a timing light, you can be sure.

--Paul

Fawkes · Apr 15, 2004

Is it doing it under acceleration or deceleration?

65fastback2+2 · Apr 15, 2004

Fawkes said:
Is it doing it under acceleration or deceleration?

cruise and decel.

Fawkes · Apr 15, 2004

Could it be an exhaust leak? I've had similar happen, but it mostly happened while decelerating.

Pakrat · Apr 15, 2004

Are you still running points under the distributor? If so, your gap may be off and in need of re-adjusting.

65fastback2+2 · Apr 15, 2004

Pakrat said:
Are you still running points under the distributor? If so, your gap may be off and in need of re-adjusting.

i have no clue, i was told its a stock 68 302 motor, so Im assuming it uses points, need to upgrade that huh??? I know its not an exhaust leak cuz I just had all new exhaust put on it today.

65fastback2+2 · Apr 15, 2004

ok, i adjusted it clockwise a lil, still the same problem, except this time i paid attention. It does this slight putting under idle, rev, decel, and cruise. So is it still timing or points???

65fastback2+2 · Apr 15, 2004

instead of messing with the points should I just upgrade to a petronix ignitor???

Ozsum67 · Apr 15, 2004

OK, first, if you turn the dist clockwise, it will increase the timing. Points are ok, you just need to replace em about once a year. If it pops under deacceration, if may be backpressure and like someone said, an exhaust leak. But you would here the leak ALL the time. You may have a burnt valve. I could talk you through the sequence if you have a vacumm gauge. You just need to advance the timing until it pings under hard acceleration, then back it off a tad.

65fastback2+2 · Apr 15, 2004

well id think a burnt valve except both sides do it, and i doubt both heads have burnt valves, and like I said I i just had all new exhaust put on today so thats not it. timing or points are all i can figure from the info in this thread so far.

Ozsum67 · Apr 15, 2004

65fastback2+2 said:
well id think a burnt valve except both sides do it, and i doubt both heads have burnt valves, and like I said I i just had all new exhaust put on today so thats not it. timing or points are all i can figure from the info in this thread so far.

How do you know it's from both sides? Did you have them put on an H pipe or some other crossover? New exhaust doesn't mean squat. Maybe you had a moron installer. Points mainly cause a miss, liike aplug was fouled. Not a pop. Timing too far out will pop and backfire through the carb. We really need more to go on here. Like a crystal ball.

65fastback2+2 · Apr 16, 2004

Ozsum67 said:
How do you know it's from both sides? Did you have them put on an H pipe or some other crossover? New exhaust doesn't mean squat. Maybe you had a moron installer. Points mainly cause a miss, liike aplug was fouled. Not a pop. Timing too far out will pop and backfire through the carb. We really need more to go on here. Like a crystal ball.

Theres no h or x pipe, no crossover. And I say it comes from both sides because you can hear the sound coming from different sides of the car, and you can sorta feel it through the floor too. I already checked the manifold gaskets and bolts, and I watched the guy do the exhaust, there are no leaks, and it was also doing this before the new exhaust. And it is a missing sound, you just kinda hear a poof sound, not really a pop its wayyy to quiet to be a pop. I know you need more info, but thats really all I know right now.

crushnut · Apr 16, 2004

I pretty sure i understand what you are talking about, because my car does the same thing. I also have dual exhaust with no crossover, and i think that may have something to do with it Putting in a crossover blends the two sides together and you probably wouldn't be able to hear it anymore after putting one in, am i right about this guys?

65fastback2+2 · Apr 16, 2004

its not supposed to do it i know that crush

mustangman1974 · Apr 18, 2004

From what I have read its an ignition problem. check the Dwell. It shoudl stay pretty steady at all rpms. varying abotu 1 degree might be ok wiht points, but it really shouldn't vary. I would also get a vaccuum and compresson guage and do a compression test on each cylinder. Then use vaccum guage to check the valves. One thing for sure you can check is to put the vaccuum guage on full port vaccum and the needle should be stead with in vary with in 1-2 in.hg If it does you got other problems especially if the timing and dwell are correct.

Ozsum67 · Apr 18, 2004

mustangman1974 said:
From what I have read its an ignition problem. check the Dwell. It shoudl stay pretty steady at all rpms. varying abotu 1 degree might be ok wiht points, but it really shouldn't vary. I would also get a vaccuum and compresson guage and do a compression test on each cylinder. Then use vaccum guage to check the valves. One thing for sure you can check is to put the vaccuum guage on full port vaccum and the needle should be stead with in vary with in 1-2 in.hg If it does you got other problems especially if the timing and dwell are correct.

Ignition problem? Huuuuuuuuuuuuuhhhhh?

littlered1 · Apr 18, 2004

Find someone with a timing light, then set the timing so you can get that out of the way for sure. After reading these posts seems like you have been guessing and just turning the distributor to wherever. Either find a friend that has one, or go out and buy one. This will always come in handy. Timing is the biggest problem with most cars that can be fixed as easy as going down to schucks, putting that gun on your #1 wire, and pointing it. Just make sure this is not the problem before you start crossing things and spending money on things that do you absolutely no good.

TobyGaff · Apr 18, 2004

The last car that I saw do this had the idle screws turned out too far on the carb. As you decelerate, it is allowing too much fuel into the engine. Turn your idle screws in 1/4 of a turn and see if it makes a difference, if not, turn them back out.

Ozsum67 · Apr 18, 2004

TobyGaff said:
The last car that I saw do this had the idle screws turned out too far on the carb. As you decelerate, it is allowing too much fuel into the engine. Turn your idle screws in 1/4 of a turn and see if it makes a difference, if not, turn them back out.

Those screws only effect mixture at idle and are bypassed soon after ANY acceleration.

slight popping and backfiring

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