Sputter / backfire FiTech fuel injection (UPDATED)

70 Challenger / 340 / MP electronic ignition with Orange box (>20yr system), Fitech fuel injection.

Car has been running great since the Fitech install over a year ago. I mainly just cruise the car. It never really gets over 2500 RPM since I have 518 OD.

Other day I got on the gas and it sputtered and seemed to backfire. Did this several times each time I jumped on the pedal. Once I let up, it ran great as usual.

Any thoughts on where to look to figure this out?

Thx

Fuel pressure low or filter clogged,old fuel maybe. I'd check ignition timing and make sure your vacuum and mechanical advance are functioning properly.Is there any self diagnostic modes/codes that can be retrieved from the FItech unit,sensors and the like?

Backfiring is typically a timing issue.

Don't rule out plugs or wires either,it could be that simple.

pending what Fitech he has some call out for dizzy to be locked out and the fitech takes care of the timing curve. look at that as well as all the fuel filters, and pressure etc..

Check all the above and drive the snot out of it so the self learning algorithm can do its thing. Sounds like you baby it a bit and the computer doesn't get much of a chance to learn above 2500. Maybe shut the OD and converter lock (if so equipped) for a while if you're not into thrashing your baby.

All good input,

I'll look over the plugs and wires
Look for vacuum leaks
Check the timing
I don't have FiTech controlling the timing.

I was wondering if it needed to learn the WOT.

Yes the fitech needs to learn all variables and scenarios, you can go in and adjust some settings for those conditions as well.
Doing some data logging will help you correct some of the adjustments.

Backfired out the exhaust or the intake? IAC reading on the handheld?

I'm pretty sure it backfired through the manifold.
I wasn't looking at the handheld

Is fhe IAC set up during install, like an idle adjustment.
I remember during the initial install the car wouldn't idle and ran like crap until I got a setting to 6-8. Seemed to recall that was the IAC?

Be pretty hard to backfire out the exhaust, that would be a misfire.

He’s likely asking about the IAC to see if it’s still working after the backfire. Though, it has nothing to do with a backfire.

I suppose if it’s lean enough you can get a backfire, I would log and see what’s happening. Most time people jam on the throttle and have an issue is because they need more accel or fast accel fueling.

Oh? Excessive fuel in the exhaust system that ignites is a "backfire" where I come from.

How dare you question the Mighty Supercuda.

Get over your self.

A backfire fires backward, out the intake. A fart out the tailpipe is a misfire. two completely different problems.

Easy, killer.

Society has been referring backfires out the tailpipe since cars have been running. It is accepted terminology in the industry.

As mentioned it could be a lot of issues, but the Fitech sets codes, look on your controller and see what if any codes have been set, if no codes are set, I would look at ignition system first. The other thing to check is that there is a filter screen on the pressure regulator valve if you take it out. I have had the one on mine get clogged and it caused it to run bad. The injector drivers in the computer will shut down if you have to much fuel pressure, it takes more amperage to lift the pintle off the seat of the injector.

https://en.wikipedia.org/wiki/Back-fire

First sentence says it all.

Right On! Mighty backfires on a car of mine blew the muffler completely off. They were LOUD! I discovered it would happen after I hooked an AIR pump up on my Mercedes but did not use the Anti Backfire Valve. When I took foot off the gas, extra fuel got sucked out of the carb and when it came out the exhaust valve and ran into that nice stream of fresh air the explosion could be heard for quite a ways. I thought it was funny until the muffler got blown off. The outside of the muffler had flattened right out and the insides were bouncing on the pavement. Then I had to buy a new muffler and figure out how to avoid the backfires.

R.

Update,

I checked the plug wires and noticed some cracks in the outer rubber.
I had another set, so I replaced them and took the car for a ride.
No backfire and ran great. Coincidence or could that have been it?

Not a coincidence. I've seen plenty of bad plug wires that didn't even look bad.

I'd say that would do it. Crossfire.

oh, wikipedia, lol. Wikipedia is only as smart as the last idiot to edit it.

What's next? Snopes?

Yep that will do it. Bad wires will cause a misfire which dumps raw gas into the hot exhaust system and boom, backfire.

The important lesson is that just because the engine is running poorly doesn't mean the fuel injection is bad. There are lots of things that can go wrong.

back·fire
/ˈbakˌfī(ə)r/Submit
verb
1.
(of an engine) undergo a mistimed explosion in the cylinder or exhaust.
"a car backfired in the road"
synonyms: misfire
"the engine backfired"

Cool

Farting out the tail pipe isn't a mistimed issue. It's a no fire issue and some other cylinder's residual exhaust pulse is igniting the air/fuel mixture. As evidenced by the OP's findings.

Coughing out the carb is a mistimed event.

Two different things.