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305 tho runs great cold, rough idle, sometimes dies when warm

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Old 05-12-2019, 09:37 PM
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Car: 92 Firebird Formula WS6
Engine: 305
Transmission: Auto
Axle/Gears: 373, I’m guessing
305 tho runs great cold, rough idle, sometimes dies when warm

I have a 92 Firebird Formula with 305 Tbi. It starts and runs nice when cold, although does idle kind of high. After reaching operating temp it still runs good until it is shut off. Upon restarting it idles like crap, sometimes dies. After reving it a few times it seems to straighten out but it is getting worse. Is anyone familiar with this problem and if so where do I start, thanks.
Old 05-12-2019, 10:59 PM
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Re: 305 tho runs great cold, rough idle, sometimes dies when warm

When was the last time you cleaned the throttle body and the idle air passage?

When was the last time you connected a scan tool and looked at the data stream?
Old 05-13-2019, 06:18 AM
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Car: 92 Firebird Formula WS6
Engine: 305
Transmission: Auto
Axle/Gears: 373, I’m guessing
Re: 305 tho runs great cold, rough idle, sometimes dies when warm

Originally Posted by Schurkey
When was the last time you cleaned the throttle body and the idle air passage?

When was the last time you connected a scan tool and looked at the data stream?
I haven’t done either of those things, I haven’t had the car for very long. Thanks for the ideas now I have a place to start
Old 05-23-2019, 01:26 PM
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Car: 92 RS - Fully Restored w/Custom Int
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Re: 305 tho runs great cold, rough idle, sometimes dies when warm

Check the other thread where I explained how a bad fuel pump/inlet hose was the problem in my case.
Old 05-25-2019, 06:14 PM
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Car: 86 IROC Z, 92 RS
Engine: 305 4bbl, 305 TBI
Re: 305 tho runs great cold, rough idle, sometimes dies when warm

Originally Posted by FormulaBerny
I have a 92 Firebird Formula with 305 Tbi. It starts and runs nice when cold, although does idle kind of high. After reaching operating temp it still runs good until it is shut off. Upon restarting it idles like crap, sometimes dies. After reving it a few times it seems to straighten out but it is getting worse. Is anyone familiar with this problem and if so where do I start, thanks.
I had a similar problem, and it was the o2 sensor, but no code. When was the last time you replaced it? They gunk up with carbon over time.
Old 05-26-2019, 08:08 AM
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Car: 92 Firebird Formula WS6
Engine: 305
Transmission: Auto
Axle/Gears: 373, I’m guessing
Re: 305 tho runs great cold, rough idle, sometimes dies when warm

Originally Posted by Stevolwevol
I had a similar problem, and it was the o2 sensor, but no code. When was the last time you replaced it? They gunk up with carbon over time.
Did a Tbi rebuild and now it runs great
Old 05-29-2019, 09:57 AM
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Re: 305 tho runs great cold, rough idle, sometimes dies when warm

Originally Posted by FormulaBerny
Did a Tbi rebuild and now it runs great

can you tell me how you fixed the idling problem, my car turns on altho sometimes doesnt wanna crank anymore, once its on i have to keep it revved up so it doesnt turn back off. can you give me any ideas of what it might be?? by the way i have a 84 z28 camaro
Old 05-29-2019, 10:38 AM
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Car: 92 Firebird Formula WS6
Engine: 305
Transmission: Auto
Axle/Gears: 373, I’m guessing
Re: 305 tho runs great cold, rough idle, sometimes dies when warm

Originally Posted by King E
can you tell me how you fixed the idling problem, my car turns on altho sometimes doesnt wanna crank anymore, once its on i have to keep it revved up so it doesnt turn back off. can you give me any ideas of what it might be?? by the way i have a 84 z28 camaro
I just installed a Tbi rebuild kit from Napa, while the unit was apart cleaned it real well, cleaned iac, then went through the idle reset process and now everything seems good
Old 05-29-2019, 11:20 AM
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Car: 92 Firebird Formula WS6
Engine: 305
Transmission: Auto
Axle/Gears: 373, I’m guessing
Re: 305 tho runs great cold, rough idle, sometimes dies when warm

Originally Posted by FormulaBerny
I just installed a Tbi rebuild kit from Napa, while the unit was apart cleaned it real well, cleaned iac, then went through the idle reset process and now everything seems good
But I suppose your 84 Isn’t a Tbi probably carb?
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