350 vortec problems
07-31-2008, 07:22 PM
#1
Staging Lane
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350 vortec problems i just bought a 97 tahoe from my buddy thats got some problems(the price was right!) maybee one of u guys can help
it has a 350 vortech with fuel injection (not tbi) and runs like **** at full throttle and at anthing above 3500 rpm's
also, the truck will not start unless i spray starting fluid in the intake. once thats done, the truck starts and idles fine. it pulls hard until 3500-4, then bogs down. its hard for me to distinguish it from miss-fire or lack of fuel. it will continue to rev to 5 grand.
the truck has new plugs, wires cap rotor, fuel filter, fuel pump, removed cats and installed o2 sims, nothing changed so he sold it to me.
i was thinking maybee a timing chain, i tried adjusting the timing, it made no differance at all. the crazy thing is the service engine soon light is not on. it works, but whatever is wrong isn't throwing a code.
i appreciate any suggestions also, is there something i have to do to get the computer to reconize that i changed the timing? thanks
it has a 350 vortech with fuel injection (not tbi) and runs like **** at full throttle and at anthing above 3500 rpm's
also, the truck will not start unless i spray starting fluid in the intake. once thats done, the truck starts and idles fine. it pulls hard until 3500-4, then bogs down. its hard for me to distinguish it from miss-fire or lack of fuel. it will continue to rev to 5 grand.
the truck has new plugs, wires cap rotor, fuel filter, fuel pump, removed cats and installed o2 sims, nothing changed so he sold it to me.
i was thinking maybee a timing chain, i tried adjusting the timing, it made no differance at all. the crazy thing is the service engine soon light is not on. it works, but whatever is wrong isn't throwing a code.
i appreciate any suggestions also, is there something i have to do to get the computer to reconize that i changed the timing? thanks
07-31-2008, 07:38 PM
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Staging Lane
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ill start by saying that the timing is not adjustable, so if you were turning the dizzy you didnt accomplish anything good. the timing needs to be set with a scanner to 0 that has live data readout. as for your drivability issue i would be looking at the fuel pressure. you should run it with a fuel pressure gauge on it and see if the pressure drops below specs. just because you have anew pump istalled doesnt mean its up to specs. another possibility is that the regulater under the upper plenum is leaking and flooding the engine when you shut it off and also leaking bad enough that the injecters are starving. no ses light is strange as it should throw a code if you were turning the dizzy, should of got the cam/crank correlation code. i would look into the fuel system as the culprit from what you described.
08-03-2008, 03:20 PM
#3
i just bought a 97 tahoe from my buddy thats got some problems(the price was right!) maybee one of u guys can help
it has a 350 vortech with fuel injection (not tbi) and runs like **** at full throttle and at anthing above 3500 rpm's
also, the truck will not start unless i spray starting fluid in the intake. once thats done, the truck starts and idles fine. it pulls hard until 3500-4, then bogs down. its hard for me to distinguish it from miss-fire or lack of fuel. it will continue to rev to 5 grand.
the truck has new plugs, wires cap rotor, fuel filter, fuel pump, removed cats and installed o2 sims, nothing changed so he sold it to me.
i was thinking maybee a timing chain, i tried adjusting the timing, it made no differance at all. the crazy thing is the service engine soon light is not on. it works, but whatever is wrong isn't throwing a code.
i appreciate any suggestions also, is there something i have to do to get the computer to reconize that i changed the timing? thanks
it has a 350 vortech with fuel injection (not tbi) and runs like **** at full throttle and at anthing above 3500 rpm's
also, the truck will not start unless i spray starting fluid in the intake. once thats done, the truck starts and idles fine. it pulls hard until 3500-4, then bogs down. its hard for me to distinguish it from miss-fire or lack of fuel. it will continue to rev to 5 grand.
the truck has new plugs, wires cap rotor, fuel filter, fuel pump, removed cats and installed o2 sims, nothing changed so he sold it to me.
i was thinking maybee a timing chain, i tried adjusting the timing, it made no differance at all. the crazy thing is the service engine soon light is not on. it works, but whatever is wrong isn't throwing a code.
i appreciate any suggestions also, is there something i have to do to get the computer to reconize that i changed the timing? thanks
Hey still have the cats laying around? I'll offer you some cash for them. good luck with the Tahoe man.
08-04-2008, 12:34 AM
#4
On The Tree
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^^I have to agree with trailwart. Thoroughly check the fuel. If everything you said was replaced I would be thinking towards the pressure regulator. Doesn't completely rule out a faulty fuel pump though. I have the new Snap On Solus Pro system. If you happen to know anybody with access to one you can actually do a drive test mode with it and monitor and graph what every sensor and system is doing while driving.
08-08-2008, 10:45 PM
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Teching In
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It's the cpi unit located under the plastic intake plenum.Very common problem with the 4.3,5.0,5.7 vortec engines.There's a retro fit kit that changes it to a cmpi unit which seems too be far more reliable. I replace at least 10 of them a year.
