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90 tbi 350 suburban stumbling taking off from idle

crash81

crash81

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roxboro,nc
anyone had this problem before? it runs great after you get just off idle but say you are sitting at light and go to take off it will stumble like it wants to cut off, you let up on the gas and it will pick up, or if you sit at light and keep foot on gas pedel just above idle speed it will take off fine. its just started the other day . any ideas ? :confused:



Dudley :D
 
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Fuel pump. You will soon see that it stumbles all the time, and one day it wont start. Not too hard to change. Drop tank.
 
ok sounds like a good thing to change. do any of you know if there is a upgrade fuel pump for the 90 suburban to flow more fuel? that way i want have to change again when i do the tbi mods here in a few weeks. part # on the pump would be much appreciated.




dudley :D
 
crash81 said:
got accel 300+ wires and ac plugs in it now less than 4 months old
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Take a look at your cap and rotor too! Once that checks out OK check your fuel presure, while the gauge is on there rev the motor and look for a drop in presure. Drop would indacate fuel filter plugged or the pump going out! HTH.
 
I am thinking your problem is fuel related. The fuel pump could be a suspect (as already mentioned). The problem could also be a fuel injector too. If you have a bad injector dribbling a bunch of raw fuel into your manifold, it will stumble at idle because it is flooding the engine, but cleans up as you accelerate because of the engines increased demand for fuel.
 
ive got 10 bucks on egr valve. I had that problem with mine. Every morning backing out of the drive way it would stuble and try to die then catch back up with it self rapidly and repetedly. allmost felt/ sounded like how a monster truck runs with its "surging". Asked my step dad ( life loong mechanic) what he thought and first thing he said was "egr valve" so i took and pluged the vacume line that went to it and its ran perfect ever sence. any how im not saying to do this permenently but you can try it cause it will only take a minute then if its bad get a new egr valve. blah blah blah try it
 
what fuel pump would yall run on it? something like a walbro? like i said i'm starting a tbi buil with the high flow tbi soon so if i have to replace it i only want to do it once.




Dudley
 
well after a call to cfm they said to use a fuel pump from a 454 big block aroud 95 or 96 year truck. but he wasn't sure on it being a direct replacment to my 90 suburban. my next question is has anyone here did this and did it fit ok.



Dudley
 
i am having the exact same problem in my 91 k5 blazer with TBI. ive been trying to figure it out for acouple of months now
 
k5freak44 said:
i am having the exact same problem in my 91 k5 blazer with TBI. ive been trying to figure it out for acouple of months now
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Dude, bring it over and I'll help you figure it out. I have lots of spares we can swap to test stuff. Egr is the most probable cause.
 
Two things I'd check if the fuel system is ok.

First -- Check your base timing. My 89 was running poorly, bogging off idle etc, when I checked the base timing, I was at like 15 degrees ATDC. Set it back to about 7 BTDC (factory is 0) and suddenly it ran like brand new!

Second -- Check your IAC, if it is going south, it can cause bogging problems.
 
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