this isn't a 3rd gen but sits next to one all the time LOL its a Suburban 1990 r2500 with a 454 tbi all factory it doesn't idol very well it has a steady miss it has a new fuel pump cap rotor wires plugs distributor module rebuilt pressure regulator timing checks out. it has a very small exhaust manifold leak but had that before and if i drive it before it dies at stop signs i loose power breaks i really need to get this running and dont want to put a lot of money in it if i dont have to and all i know to do is start changing part at this point any help would be appreciated. Thanks in advance

Kevin

ps also when i turn it off it has gas vapor that comes out of the top of the throttle body if that helps any. to me it might be just a result of whats wrong and the exhaust seam hotter than normal

 

Replace the injectors. They don't last forever.

 

The cones look good but if it come to just start replacing parts till i find it that will be the first thing i will change because that does make sence
why the tb is smoking like it is. but not sure about the miss being so steady. do you have any thoughts on that or should i change them and see first. Thanks for your thoughts i did think that myself till i seen that the fuel pressure was 10 lbs and changed the fuel pump and never gave it another thought till now that you said that i will look hard at that again.

btw I have changed the fuel filter too.

thanks again
Kevin

 

My 91 454SS had a miss. Always noticed it when I was stopped at a light. Never had a problem while driving but when stopped, the engine always seemed to have an intermittent miss. Everything else was checked out and was fine. I also thought it was an ignition problem.

Replaced the injectors and the miss went away. 454 TBI injectors are not the same as SBC injectors. They're larger because they flow more fuel. They also cost more. Mine were $150 each.

TBI fuel pressure operating range is 9-13 psi.

If you don't want to "guess" at what might be wrong, take it into a dealer and have them diagnose the fault. If the injectors are original, they're 18 years old and have gone through a lot of duty cycles.