454 TBI issues.

[thelincolnguy]

Hello, I have recenly been having an issue with my 1989 chevy r3500. it has the 454 tbi. when i start the truck up and put it in drive it will drive fine at any speed until it warms up a bit. Then itll start popping and cracking and acting like it wants to cut off. The more i try to get into it the rougher it runs. also when its idling it smells like straight gas and i sometimes see white smoke coming from the right exhaust pipe. moreso when its been idling for a while. the truck only had one oxygen sensor when i bought it, and when i installed headers i accomodated for it. please help! this truck has become virtually undrivable and once was my daily driver. it has new left side fuel tank, pump and sending unit. ran it with straight headers for about 15 miles before i built the exhaust if that matters. thanks- Eric.

[Irish_Alley]

http://forum.73-87chevytrucks.com/smforum/index.php?topic=29996.0
sounds like a sensor going out. the reason it runs fine before is cause its running in "open loop" where the engine runs based off a presetting  regardless of sensor feed back. then once a certain criteria is met the engine goes into "closed" loop where sensor input whill change how the engine is running.

[Gwtt]

do you have a check engine light?
I would drive with a fuel pressure gauge and drive it and see if you loose pressure. if you don't loose pressure I'd look towards,
Does the truck have catalytic converters? - once they get hot they plug up. (swell)
did you replace the O2 sensor? once they are covered in fuel they are junk. i would replace the sensor.
I would also disconnect the battery and hold the battery cables together for at least a minute.
make sure your temperature sensor is reading correctly, use a thermo temp gun to verify.
EGR valve (is applicable) can cause head aches.

[thelincolnguy]

That makes sense about closed loop only. This truck has no catalytic converter,but it does have a single upstream sensor. the sensor is new along with headers and dual exhaust. and whatever sensor that is on the passenger side of the block is not wired correctly. and where is the egr valve located on the 454??

[Irish_Alley]

that would prob be the knock sensor on the passengers side. its there to sense pre detonation and retard the timing