LT1 Based Engine Tech 1993-1997 LT1/LT4 Engine Related

lt1 bogging idle issues

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Old 02-28-2018, 07:15 PM
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lt1 bogging idle issues


New to the site not a mechanic so bare with me in correct wording...bought a 97 z28 from somebodyhas a lt1 motor in it first problem I dealt with was a no spark changed the opti fixed the issue but now takes a couple cranks to turn over and run at idle...when running on idle seeing no issue when u step on pedal to hit the gas bogs down even if taking a ride around 1500 2000 rpms constant sputter bog feels like maybe a fuel air problems but I don’t no list of stuff done new opti new plugs wires coil map sensor tps sensormaf sensor crank position vehicle speed sensor o2 sensor battery scanned for codes only shows rear o2s and egr but the guy I bought it from deleted egr and has long tube headers so no rear o2s I ran a live data on car maybe this could help...just looking for right direction some say vacuum lines some say Possible clogged
injectors injectors
or idle air control..






Last edited by Nightrider1984; 02-28-2018 at 07:31 PM.
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Old 02-28-2018, 08:28 PM
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Re: lt1 bogging idle issues

Have you checked the fuel pressure? I know that when mine had a bad fuel pump it would be hard to start and bogg down and sputter. Also could be a really dirty fuel filter.
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Old 02-28-2018, 08:57 PM
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Re: lt1 bogging idle issues

The huge “+” fuel trims on both sides indicates it’s running lean.

See post #2 above.
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Old 03-21-2018, 10:16 PM
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Re: lt1 bogging idle issues

Ok so I've been at this for awhile still running lean but new fuel filter checked all injector all working properly and friend sometimes getting a tune helps so I got a mail order power tune from lt1pcmtuning throw pcm back in cranks won't staying running so I took some carb cleaner sprayed the carb fires right up that cuts off could it be a leaky injector or is something else I could check for just need some advice or direction to check no vacuum leaks that I could find new air filter could it be iac valve? Or possibly the carburetor needs to be adjusted ?
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Old 03-21-2018, 11:01 PM
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Re: lt1 bogging idle issues

Originally Posted by 97rebuiltZ28
Have you checked the fuel pressure? I know that when mine had a bad fuel pump it would be hard to start and bogg down and sputter. Also could be a really dirty fuel filter.
Originally Posted by Nightrider1984
Ok so I've been at this for awhile still running lean but new fuel filter checked all injector all working properly and friend sometimes getting a tune helps so I got a mail order power tune from lt1pcmtuning throw pcm back in cranks won't staying running so I took some carb cleaner sprayed the carb fires right up that cuts off could it be a leaky injector or is something else I could check for just need some advice or direction to check no vacuum leaks that I could find new air filter could it be iac valve? Or possibly the carburetor needs to be adjusted ?

1. Did you check the fuel pressure, as asked in post #2? If so:

- what is the pressure when the pump primes, without starting the engine?

- after the pump shuts off, how fast does the pressure drop?

- at idle, what is the fuel pressure with the vacuum compensation line off the fuel pressure regulator?

- what does the pressure drop to when you reattach the vacuum line?


2. “Carburetor”..... ? ? ? ?

Last edited by Injuneer; 03-22-2018 at 06:52 PM.
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Old 03-22-2018, 03:56 PM
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Re: lt1 bogging idle issues

OP

you need to check fuel pressure before you do anything else
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