A couple hiccups can’t figure out

[StevenB]

Iv got a 95 2500 454 with 230,000 miles on it, Iv put in new tps, map sensor, idle air control valve, rebuilt tbi, temp sensors, plugs, wires, cap rotor, coil, fuel pump, fuel filter. Runs good injectors spray fine but after start up will stumble and die about midway between cold and operating temp and does same when put into reverse but if you feather the throttle it’ll pull out of it. Doesn’t do it when it’s completely warmed up. Another thing is while driving if given a lot of throttle it back fires in the intake kinda sluggish does just fine putting around though. I was thinking of throwing new distributor in cause I’m pretty sure this is the original one in it and it’s kinda crusty inside. It’s only had a check engine light once and the tps and map replacement fixed that, Thoughts? Thanks.

 

[wezmykat]

"doesnt do it after it's warm"
#1 vacuum leak(s)
#2 intake manifold gasket is shot
comes to mind

 

[StevenB]

Yeah as far and the stumble and trying to die it’s fine when warm, still will pop in intake when warm though. I tried the carb cleaner around stuff and didn’t notice a difference but doesn’t mean there is a leak necessarily

 

[PlayingWithTBI]

It sounds like you're getting lean pops. What's you fuel pressure? IIRC for 94 - 95 it s/b 28 - 32 PSI

 

[StevenB]

Haven’t got to checking the fuel pressure yet, assumed should be fine with the new pump and everything. Was doing the same thing before I did the pump also

 

[PlayingWithTBI]

Haven’t got to checking the fuel pressure yet, assumed should be fine with the new pump and everything.

Trust but verify

 

[Nad_Yvalhosert]

It sounds like you're getting lean pops. What's you fuel pressure? IIRC for 94 - 95 it s/b 28 - 32 PSI

Huh? TBI is regulated at 9-13 psi. That kind of pressure will either blow out the regulator, or run so rich it'll foul the plugs on the way to Walmart.

My '95 c2500 and its bone stock 5.7 runs at 12 psi at idle.

 

[PlayingWithTBI]

My '95 c2500 and its bone stock 5.7 runs at 12 psi at idle.

The 5.7L is 11 - 13 PSI, the 94 - 95 7.4L uses smaller injectors at higher pressures.

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Here's my 61LB/HR injectors running @28 PSI on a 5.7L. They're capable of holding that pressure as long as you have good O-rings

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[Nad_Yvalhosert]

The 5.7L is 11 - 13 PSI, the 94 - 95 7.4L uses smaller injectors at higher pressures.

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Here's my 61LB/HR injectors running @28 PSI on a 5.7L. They're capable of holding that pressure as long as you have good O-rings

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Interesting. I'm not as familiar with the last TBI 454's as I'd like. Thanks for the enlightenment!

I'm imagining increased atomization and perhaps an incremental increase in MPG on the 5.7?

Did you throw in a wideband O2 or a HO2S in the mix?

 

[PlayingWithTBI]

I'm imagining increased atomization and perhaps an incremental increase in MPG?

You definitely get a huge cone and at idle, you have to watch for stumbling/surging from the fuel dripping off the sides but, as soon as you get off-idle it does come in better. I wound up taming it down to 20 PSI with my bored 46mm TB (and bored to 48mm Edelbrock 3704 manifold) and the same flow matched 61 LB/HR injectors

There's a lot more you can do with TBI than most people think, it's quite a robust system and, fun to play with!