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Old 11-03-2011, 01:48 PM   #1
victor3ranger
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Default Chevy TBI guru's please help

I need some help with my truck, I am about to pull my hair out trying to figure out what is causing my truck to run like shit.
It is a 1995 GMC Z71 with a TBI 350.
When driving at any speed it acts like it has water in the gas, spits, coughs, feels like a misfire.
I have been dealing with this off and on for the past year, now it is doing it all the time. At first I thought it might be the ethenol in the gasbut now not so sure.
Changed cap, rotor, wires, plugs, ect, pickup coil, nothing helps. When it is hot and dry outside the problem seems to go away. But when it gets cold or wet it starts back up again.
Would the EGR valve couse something like this? Anything else to check?
Check engine light doesn't come on either.

Anyone got any ideas??

Last edited by victor3ranger; 11-03-2011 at 01:51 PM.
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Old 11-03-2011, 01:54 PM   #2
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Default Re: Chevy TBI guru's please help

Check fuel pressure
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Old 11-03-2011, 02:06 PM   #3
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Default Re: Chevy TBI guru's please help

I have checked the fuel pressure before and it was within spec but I will check that again.
Any other ideas??
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Old 11-03-2011, 03:24 PM   #4
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Default Re: Chevy TBI guru's please help

use a ac delco cap, ive seen those new be an issue.
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Old 11-03-2011, 03:31 PM   #5
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Default Re: Chevy TBI guru's please help

Check e.c.t sensor
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Old 11-03-2011, 03:36 PM   #6
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Default Re: Chevy TBI guru's please help

Two problems Ive had with them is the temp sensor for the computer have a short in the wire and cause similar symptoms all the way to the point it would die at lights if you didnt give it gas!

The other is the wiring going to the coil also have a short and it would run shitty, spit sputter and often times not even crank.

goodluck
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Old 11-03-2011, 03:50 PM   #7
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Default Re: Chevy TBI guru's please help

GT 350, what is the ect sensor?? where is it located?

slow3rdgen, is the temp sensor on the front of the intake manifold? Also, you talk about a short in the wire going to the coil, do I just check that by tracing the wires from the distributor back to the computer?

And trace the wire from the temp sensor all the way back to make sure its ok???

Thanks for the info guys, keep giving me ideas, this thing is driving me nuts.
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Old 11-03-2011, 04:06 PM   #8
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Default Re: Chevy TBI guru's please help

Had dist shaft bushings cause issues, most of the time all that goes wrong with them is fuel pressure though. Under the dash on right side is the connector for checkig timing, basically bypasses the ecu for timing, disconnect it and drive it, if it quits the misfires etc(will be lazy) then most likely is dist bushings or magnet on shaft cracked.
Could also be a bad ign coil.
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Old 11-03-2011, 04:09 PM   #9
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Default Re: Chevy TBI guru's please help

check the knock sensor and the tps
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Old 11-03-2011, 04:10 PM   #10
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Default Re: Chevy TBI guru's please help

Quote:
Originally Posted by victor3ranger View Post
I need some help with my truck, I am about to pull my hair out trying to figure out what is causing my truck to run like shit.
It is a 1995 GMC Z71 with a TBI 350.
When driving at any speed it acts like it has water in the gas, spits, coughs, feels like a misfire.
I have been dealing with this off and on for the past year, now it is doing it all the time. At first I thought it might be the ethenol in the gasbut now not so sure.
Changed cap, rotor, wires, plugs, ect, pickup coil, nothing helps. When it is hot and dry outside the problem seems to go away. But when it gets cold or wet it starts back up again.
Would the EGR valve couse something like this? Anything else to check?
Check engine light doesn't come on either.

Anyone got any ideas??
KNOCK SENSOR IS BAD
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Old 11-03-2011, 04:19 PM   #11
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Default Re: Chevy TBI guru's please help

BIGZEK, where is the knock sensor located??

tsanchez, I will get in touch with a friend of mine and see if he can check the timing for me.

Is it possible that the injectors could be going bad???

Last edited by victor3ranger; 11-03-2011 at 04:24 PM.
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Old 11-03-2011, 04:24 PM   #12
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Default Re: Chevy TBI guru's please help

Quote:
Originally Posted by victor3ranger View Post
GT 350, what is the ect sensor?? where is it located?

slow3rdgen, is the temp sensor on the front of the intake manifold? Also, you talk about a short in the wire going to the coil, do I just check that by tracing the wires from the distributor back to the computer?

And trace the wire from the temp sensor all the way back to make sure its ok???

Thanks for the info guys, keep giving me ideas, this thing is driving me nuts.
Its the sensor right by the thermastat housing in the intake ...the knock sensor should be on the back side of the block at where the bell hosing meets at the top ...or on the side of the block it will look like a white mushroom ...
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Old 11-03-2011, 04:24 PM   #13
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Default Re: Chevy TBI guru's please help

Quote:
Originally Posted by victor3ranger View Post
BIGZEK, where is the knock sensor located??

tsanchez, I will get in touch with a friend of mine and see if he can check the timing for me.
under driver side exhaust manifold ....when they go bad they are trying to adjust timing ....it throws the fuel curve out of wack
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for instance, a intelligent alien species somewhere in the oldest part of the universe, sent out spores packed with DNA in a explosive manner like a super nova.
currently working on 540 ....
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Old 11-03-2011, 04:26 PM   #14
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Default Re: Chevy TBI guru's please help

Great info guys, those two things should be easy to check and cheap to replace.
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Old 11-03-2011, 06:23 PM   #15
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Default Re: Chevy TBI guru's please help

Knock sensor is on pass side just ahead of starter near motor mount.
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