Nasty backfire

[DanDalessandro]

Hey guys. Finally got the car out of the garage the other day. I stalled it a couple times because it wouldn't idle. Finally got it going and took it around the block and it ran alright. Went back into the driveway and it Idled real nice with what sounds like a hairline miss.
Had to run to the store so I parked it. Came back to start it about a half hour later and it backfires twice out the intake.
It burned the map sensor, so I replaced it and put the little seal back on too. Try and restart it and it backfired out the exhaust this time.
Pulled #1 plug and it didn't look too bad. Put it back in and tried it again. It ran for about 30 seconds before it backfired out the exhaust again.
Car has ported heads, a cam, 36 lb injectors, stock fuel pump, and 24x swap.

Thoughts? Advice?

[farmington]

Has it been tuned yet?

[DanDalessandro]

Yes

[zeeman]

It's pink. I'd backfire too If I was pink. I got nothing helpful Dan

[s.reef]

Optispark

[DanDalessandro]

What is that?
Couple friends think it's a wiring issue

[s.reef]

What is that?
Couple friends think it's a wiring issue

Could be a bad coil pack.

[98blackbeauty]

Well sounds like you have a bad injector dripping gas, and when you go to start the spark gives the backfire from the excess gas. Your timing could also be off. And yes the dreaded opti spark. Do you have a timing light? clamp it on a spark plug wire and shoot it into your hand or dark spot watch the repetitive light rate, go down each wire. I have found real intermitent wires this way. if it all looks good then go for the injectors. Do you have original injectors put them in see if you still have same problem.
This is tough problem because you have to separate Mechanical(injectors) from electrical (spark plugs). Also what plugs are you running?

[DanDalessandro]

I don't have an optispark anymore. I have ls ignition now. The wires are Taylor and they are kind of well, to put it easy, shit. They don't like to stay on the coil all the way, so I'm making msd wires.
I run autolite 104 gapped to .035 as recommended by Lloyd Elliot.
I'm going to replace wires, plugs, and any coil that had fouled out plugs first. I get all 8 plugs for 8 or 10 bucks, so.
I can't swap back to stock injectors as the tune is for 36 lb, not the stock 24.

[DynoDave]

I've never seen a MAP burn like that. Is that a "thing"? Do they fail that way? Or is that an indicator of another issue?

[DanDalessandro]

I've never seen a MAP burn like that. Is that a "thing"? Do they fail that way? Or is that an indicator of another issue?

The map burned just because it was backfiring out the exhaust and that was the path of least resistance. I replaced the map with an oem one and nothing changed

[1BADAIR]

Did it ever run right? When Ryan did his the conversion harness for the injectors was wired wrong and they would fire out of sync causing fuel to puddle in the intake

[DanDalessandro]

It ran what I would call right when I pulled it out of the garage and got it on the road. Drove find, no backfiring. Parked it and let it idle and idled fine.

[98blackbeauty]

Well based on what you said, I am leaning towards injectors, but are you sure you have correct wires on correct firing order of plugs. Sometimes you have to relook several times. Have you tried my suggestion with timing light? Your looking for irregular firing on some plugs.

[zeeman]

Check your fuel pressure Dan. Running, static and leak down. If an injector is leaking it will not hold presure. Popping back through the intake can be caused by a lean condition.
It does sound timing related but you gotta start somewhere