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Author Topic: 350 TBI runs rough  (Read 4535 times)

Offline jdusten

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350 TBI runs rough
« on: August 20, 2016, 09:06:08 pm »
I know this has been posted a gazillion and 2 times but I can't find any information that's helped. About a month ago I bought an 87 silverado 350 tbi with a turbo 350. It's got a new fuel filter, plugs, wires, egr valve, vacuum lines, coolant temp sensor,  and the distibutor cap looks fairly new (haven't checked the rotor) well it runs like plain poo and I've been pulling out my hair trying to figure out what's wrong. It takes a few seconds of turning over to finally start, then it idles high (no tach so I'm not sure of exact rpm but you can easily tell by the sound) after a few seconds it drops rpm but still idles high. Once put in gear it sounds like it idles pretty good. However when taking off from a stop it falls on it's face, it spits and sputters and stalls for a second before catching itself back up and taking off as well as just lacking power over all. If you're going about 30ish and hammer it it takes off pretty well but still runs kinda rough. Any help would be greatly appreciated
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Offline Irish_Alley

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Re: 350 TBI runs rough
« Reply #1 on: August 21, 2016, 03:20:19 pm »
does it smoke?
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Offline jdusten

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Re: 350 TBI runs rough
« Reply #2 on: August 22, 2016, 08:37:04 pm »
Not at all
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Offline XrayTedd

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Re: 350 TBI runs rough
« Reply #3 on: August 23, 2016, 08:32:56 am »
This is what's known as the TBI gremlin. The TBI is a great motor but once it developes a problem it can be difficult to chase out. 
I would start by checking all your grounds. Then from there check your timing. Don't forget to disconnect the est wire to do this. Some of the symptoms you mentioned sounds like the TPS. Check the easy stuff first then move on to the TPS.

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Offline Irish_Alley

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Re: 350 TBI runs rough
« Reply #4 on: August 23, 2016, 08:49:18 am »
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Offline Jason S

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Re: 350 TBI runs rough
« Reply #5 on: August 23, 2016, 10:20:04 am »
While doing the other tests, it'd be worth checking for vacuum leaks from the throttle body to intake gasket.
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Offline Irish_Alley

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Re: 350 TBI runs rough
« Reply #6 on: August 23, 2016, 10:50:35 pm »
Quote from: Jason S on August 23, 2016, 10:20:04 am
While doing the other tests, it'd be worth checking for vacuum leaks from the throttle body to intake gasket.
this area is very prone for leaks
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If you can’t tell yourself the truth, who can you tell it to?~Irish_Alley

When you have eliminated the impossible, whatever remains, however improbable, must be the truth ~Sherlock Holmes

Offline jdusten

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Re: 350 TBI runs rough
« Reply #7 on: August 24, 2016, 11:03:56 am »
Well last night I bought an intake and carb off a buddy. Standard gm spread bore intake with a square bore holley (don't know the specs but they were cheap so you guys know how it is lol) besides the adapter plate and gaskets, is there any other parts I'll need for the swap?
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Offline XrayTedd

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Re: 350 TBI runs rough
« Reply #8 on: August 25, 2016, 09:56:02 am »
Unless the intake came off a motor with TBI heads you'll have to modify the center mounting holes to fit the angle. 86 and earlier heads have a different angle than that of the 87-95 heads.

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