Help! Major Problem!

I have a 1990 454 SS. The truck idles fine. But when your driving and push the gas more than a quarter of the way down its bogs down REALLY bad,will not accelerate and almost dies. Ive timed it to different marks atleast 10 times, changed the distributor,plug wires, spark plugs, coil,tested the map sensor,changed the fuel filter and tried some fuel system cleaner, took the tbi off to see if it was clogged somewhere. My dad thinks i need to get a new tbi but i dont know yet. Does anyone else have any suggestions.Any help would be appreciated....


Thanks,
Kyle

Check the MAF (Mass AirFlow sensor). The computer may be seeing too much or too little air coming in, and flooding, leaning out the engine. Is this all the time, or just from a stop/just while moving?

1990 doesn't have a mass air flow sensor, it is a speed density system. Does the problem occur all the time or only when cold? Have you checked the fuel pressure? My 1993 Suburban was doing the same thing but only when cold. Problem turned out to be a blocked heater line (was blocked at quick release at engine block). If your heater does not get warm you may want to check that, the lack of circulation was keeping the back of the motor too cold so when it was warming up it was getting too lean.

How does it run otherwise? How about a restriction elsewere? Perhaps a plugged catalytic converter? When you rev it, how does the exhaust seem to flow out of the tail pipe?, you could try dropping the cat off of the manifold pipes and see how it goes then.

THe problem happens all the time, and it gets worse everytime i drive it. Im thinking it might be the TBI,it may be clogged up, so we are getting a new one for it, if that doesnt help it i will check the fuel pump. I took the cat off the other day cause i thought that was the problem. Any 454 throttle body from 87 to 95 should work right?






Thanks yall,
Kyle

You could look at the fuel spray from the injectors when you rev up the engine and see if it looks like it is spraying normally.

spray looks normal at idle, until you rev it up and then the fuel sprays crazy and it bogs down and almost dies

Check the fuel pressure, if it's normal (9-12 PSI) then run some SeaFoam through a tank.

Are you getting a check engine light? If so, check your catalytic converters.

look i dont know where J-RI gets his info but so far all the post i've read that he has posted are just miss-information, your fuel pressure on a 95 454 should be 25-32 by the haynes manual.
i think he spends his life on here just trying to give people bad advice.
i'ld just guess if you have the right fuel pressure that it bad injecter.

Its a 1995, not a 1990 and Jri is correct, fuel pressure should be 9-13psi according to alldata.

sorry, typed that backwards...its a 1990, not a 1995

Well, im getting tired of trying to fix the damn thing so we are taking it to a dealership, me and my dad cant find whats wrong with it..we put a new tbi on it, but it did not fix it. so we did a code test and it said something to do with the ignition timing and spark, but i dont want to mess with it anymore.....i got the truck two weeks ago and havent had one good day with it....im pissed....a warning to anyone who gets a 454 SS, they are a bitch to work on.....

Hi,I hope you find out what the prob is w/ an update.It kinda sounds to me like a friend of mine's truck that had a bad egr valve.Lots of black smoke...

The dealership told me that all i needed was a new fuel pump, which isnt to hard of a job besides spilling gas all over you. That is what i thought it was anyway. The truck is 15 years old im sure it needed a new one anyway.