Backfire and car sounds like its struggling to get gas through exhaust

Ford Guy · Apr 13, 2023

Good day all.
Hope someone can lend some advice.
Got in the ST today after work. Started it up from the office. As I approached from behind and got close, it sounded like the car was struggling to get gas through (it sounded like a pulse). Like if it was breathing but every 3 seconds or so it would sound like the battery would die from the rear...
It's been really hot lately today hitting 30 degrees Celsius. On my way home, the car was backfiring A LOT like gun shots going off and seems hesitant at certain downshifts.
Any ideas? Hopefully I conveyed the issue well enough (if it is an issue).

I have:
SPD catted down pipes
93 octane tune
Borla Atak catback exhaust (dual x pipe as a mid resonator)
JLT oil catch can

Tks.

TMac · Apr 13, 2023

I think you need to restate the problem in words that can be understood. I don't know how a car sounds when it's "struggling to get gas through". As far as "it was breathing but every 3 seconds it would sound like the battery would die from the rear" I can only say "what?". This sounds more like a person suffering from extreme flatulence leading to a heart attack than a car.

When did you put on the exhaust? While I don't understand what you're saying, a new exhaust- downpipes, and exhaust, combined with backfires would make me think about an exhaust leak.

Did it throw any codes?

Ford Guy · Apr 13, 2023

TMac said:

Lol. Sorry I tried.
All the mods have been on for at least a year now. I recently had exhaust work done (I tried straight pipe, rear muffler delete, etc.) and since I've noticed "hesitation" or a "pulse" sound. I equated it to a person who is struggling with their breathing. I cold started the car and as I listened from the rear, every 3 seconds or so it sounded like it was hesitating or struggling to get gas through and sounded like a pulse. Hard to describe idk.
When I downshifted from third to 2nd around 40km/h it started to backfire as if the car was going to cut out like there wasn't enough pressure to get the gas through.
A friend said it might be an exhaust leak. Could a leak in the exhaust cause this to happen? Maybe its the air/fuel ratio?
It seems to have started since the exhaust work and since it's hit warmer weather (25+ degrees).
No codes, car drives normal aside from a lot of backfire (gun shots) which it did before but seems more today.
Hope that helps, tks.

GearHead_1 · Apr 13, 2023

Not saying I understand the description for sure but it sounds like it is simply misfiring. I'd certainly take a look at the exhaust with a fine tooth comb, next thing I think I'd do is to throw a set of spark plugs in it.

TMac · Apr 13, 2023

An exhaust leak can definitely lead to backfires, especially under deceleration. Check all the fasteners on the exhaust system, see if you can hear any audible sounds from the joints at idle. Probably not the A/F ratio or misfires as I would expect DTCs.

Ford Guy · Apr 13, 2023

GearHead_1 said:

Thanks. Can you recommend a set of spark plugs? Tks.

Cdubya · Apr 13, 2023

When's the last time you emptied the catch can? How many miles do you have? I'd be surprised if plugs had issues before 30k miles. After that, certainly the gap can get too large or other problems can blight them. Have you filled up on name brand gas or some shady gas station recently. Did you try to do a diagnostic with Forscan to see if any codes are present?

Ford Guy · Apr 13, 2023

Cdubya said:

3 weeks ago I emptied it. I empty it once a month. I have 52k kilometers/ 32300 miles. I always use name brand gas from Esso or Petro (93 octane or 94). I haven't tried forscan.
I just started the car after sitting 2hrs and it's running perfectly fine. Drove it home and it wasn't backfiring much?!?
Should I just change the spark plugs?
Is there a special type of spark plug you guys recommend or simple Ford ones?
Tks.

GearHead_1 · Apr 13, 2023

Ford Guy said:

I've been running NGK's Ruthenium plugs and have had no problems. The truth is I haven't put a set in my Xploder as it only has 6,000 miles on it. I have run them in my 3.5L Boost. The choice of spark plugs is like picking a motor oil. For every good review, you'll find one where someone didn't feel the same way. You won't have issues with Motorcraft plugs either.

Ruthenium or Irridium seems to be the trend for plugs today. Those precious metals more than anything help determine how long a plug will last. I've never tried to find out how far a plug will go. I change them far more often than recommended. I had the opportunity to visit a spark plug factory years ago. The one thing I remember them saying more than anything else is that a spark plug has a very simple job to do.

Cdubya · Apr 13, 2023

Cant really fault just getting the Ford recommended Motorcraft plugs which are Iridium. Not sure if you can get stuff from Rockauto but their OE stuff is pretty cheap.

Ford Guy · Apr 13, 2023

GearHead_1 said:

I've been running NGK's Ruthenium plugs and have had no problems. The truth is I haven't put a set in my Xploder as it only has 6,000 miles on it. I have run them in my 3.5L Boost. The choice of spark plugs is like picking a motor oil. For every good review, you'll find one where someone didn't feel the same way. You won't have issues with Motorcraft plugs either.

Ruthenium or Irridium seems to be the trend for plugs today. Those precious metals more than anything help determine how long a plug will last. I've never tried to find out how far a plug will go. I change them far more often than recommended. I had the opportunity to visit a spark plug factory years ago. The one thing I remember them saying more than anything else is that a spark plug has a very simple job to do.

Ok cool. Lol@exploder haha.
Appreciate the help.
Tks.

Ford Guy · Apr 17, 2023

Plugs changed and exhaust leaks fixed.
Big time difference in the way the car is running now! Old plugs were at 34,new ones gapped to 28.
Car isn't backfiring as much but still get the random gun shots lol.
I have noticed that after filling up with 93 octane I hear that pulse noise again coming from the exhaust tips.
As if the gas is struggling to get through.
Every 2-3 seconds I hear the exhaust tone drop as it idles and then bounces back to normal and then down and down and up.
Driving I don't feel or hear any difference. It's typically after filling up and at idle.
I also noticed recently on cold starts when I reverse down the driveway the car shakes a bit?
Any ideas what that could be?

Cdubya · Apr 17, 2023

is your idle rpm fluctuating? Id keep a close eye on what its doing. sounds like your car is stumbling or something. Ive had intake leak on a previous car do similarly. Like i said, doesnt hurt to do a forscan diagnostic and see an what codes come up also.

you should definitely flash to stock tune to see if still behaves like that. Maybe even consider removing the catch can just to take it out of the equation also.

Ford Guy · Apr 19, 2023

Cdubya said:

Haven't noticed any fluctuation.
Cold starts in the cold morning and it's shaking (rough idle) until the valves close.

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