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Rough Idle

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Old Mar 13, 2012 | 04:52 PM
  #1  
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Car: 1986 Camaro IROC Z28
Engine: 5.0L 305 TPI
Rough Idle

When I first start my car up from it sitting for more then 20 minutes or so it will not idle. I have to feather the gas or else it will die. Once it gets going it runs just fine. I have seen somewhere or someone told me that the fuel filter and/or fuel pump needs to be replaced. Is that true?
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Old Mar 13, 2012 | 04:58 PM
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From: Fairview Heights Illinois
Car: 1986 Irocz
Engine: 305 TPI
Transmission: 700R4
Axle/Gears: 3.25:1
Re: Rough Idle

Originally Posted by Shane4524
When I first start my car up from it sitting for more then 20 minutes or so it will not idle. I have to feather the gas or else it will die. Once it gets going it runs just fine. I have seen somewhere or someone told me that the fuel filter and/or fuel pump needs to be replaced. Is that true?
You might have leaky fuel injector/s.
I would put a fuel pressure gauge on the rail and watch it closely.
If fuel injectors are leaking then the pressure will drop quickly when you shut off the engine.
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Old Mar 13, 2012 | 05:54 PM
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Re: Rough Idle

If I shut it off and try and start it back up it will fire up right away, even within 5 to 10 minutes. Would that rule out the leaky fuel injectors?
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Old Mar 13, 2012 | 11:20 PM
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Re: Rough Idle

I won't be checking anything on it till Easter weekend because I am away to college.
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Old Mar 14, 2012 | 02:15 AM
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From: Fairview Heights Illinois
Car: 1986 Irocz
Engine: 305 TPI
Transmission: 700R4
Axle/Gears: 3.25:1
Re: Rough Idle

Originally Posted by Shane4524
If I shut it off and try and start it back up it will fire up right away, even within 5 to 10 minutes. Would that rule out the leaky fuel injectors?
No.
That's exactly how leaky injectors act.
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Old Mar 14, 2012 | 01:24 PM
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Re: Rough Idle

Originally Posted by 305sbc
No.
That's exactly how leaky injectors act.
Alright, I see. Well, say I test the pressure and it goes down like you say it will. What all am I looking to replace?
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Old Mar 14, 2012 | 02:00 PM
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From: Fairview Heights Illinois
Car: 1986 Irocz
Engine: 305 TPI
Transmission: 700R4
Axle/Gears: 3.25:1
Re: Rough Idle

Originally Posted by Shane4524
Alright, I see. Well, say I test the pressure and it goes down like you say it will. What all am I looking to replace?
Next step is to pull the rail up with the injectors still in it and do the test again.
You should be able to see if fuel leaks from the injectors and from which ones.
Sometimes the injectors still need to be warm for them to leak during the test.
At that point you get a good idea about what is going on and what exactly is wrong and may need replaced. Then you go from there.

If injectors are bad, then most people replace them with the newer style Bosh-3 type.
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Old Mar 14, 2012 | 07:48 PM
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Re: Rough Idle

Alright, so if the pressure check out fine I should go to the fuel filter next?

If I end up having a leaky injector won't I have to replace all 8?

Last edited by Shane4524; Mar 14, 2012 at 07:57 PM.
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Old Mar 14, 2012 | 09:20 PM
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From: Fairview Heights Illinois
Car: 1986 Irocz
Engine: 305 TPI
Transmission: 700R4
Axle/Gears: 3.25:1
Re: Rough Idle

Originally Posted by Shane4524
Alright, so if the pressure check out fine I should go to the fuel filter next?

If I end up having a leaky injector won't I have to replace all 8?

Fuel filter has no effect on hot starting problems.

It's up to you how many you replace.
You can pull them all and have them all checked on a flow-bench, or mail them off to be checked.
Most people replace injectors in sets that are flow matched.
The flow-bench would show any differences in flow or operation.
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Old Mar 14, 2012 | 10:10 PM
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Car: 1986 Camaro IROC Z28
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Re: Rough Idle

Oh, alright. I have just been told the filter could be dirty. I will check it all out then. Thanks, and if anyone else has any input please tell me.
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Old Mar 17, 2012 | 04:30 PM
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Car: 1989 Trans am
Engine: 350 TPI
Transmission: 700r4
Axle/Gears: 3.27 posi
Re: Rough Idle

I would check the filter first. if thats not it, it could be the injectors. Or the fuel regulator is bad.
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Old Mar 17, 2012 | 06:50 PM
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From: Wisconsin near the 54757
Car: 1986 Camaro Z28
Engine: 385" SBC
Transmission: built out 700r4
Axle/Gears: 4th gen, 373, LSD, GIRDLE
Re: Rough Idle

Originally Posted by 305sbc
Next step is to pull the rail up with the injectors still in it and do the test again.
You should be able to see if fuel leaks from the injectors and from which ones.
Sometimes the injectors still need to be warm for them to leak during the test.
At that point you get a good idea about what is going on and what exactly is wrong and may need replaced. Then you go from there.

If injectors are bad, then most people replace them with the newer style Bosh-3 type.
bosh-3 type, where do most people buy these? because im searching summit and so far no good, and will these work for a earlier 350 car?
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Old Apr 22, 2012 | 09:39 PM
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Re: Rough Idle

Update:

I had the fuel filter replaced. I watched the auto shop do it and then they checked my fuel pressure. It ran at 35psi and when they removed a vacuum hose it went up to 45psi. They said this is normal. When I shut the car off they removed the pressure gauge before I could see if the pressure dropped right away signalling a leaky fuel injector, as sbc305 stated above.
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Old Apr 24, 2012 | 07:56 AM
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From: Adrian, Mi
Car: 1989 Camaro
Engine: 350 but it's torn down right now.
Transmission: 700r4
Axle/Gears: I'm working on it,lol.
Re: Rough Idle

Have you checked your intake manifold gaskets for leaks?
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Old Apr 24, 2012 | 05:44 PM
  #15  
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Car: 1986 Camaro IROC Z28
Engine: 5.0L 305 TPI
Re: Rough Idle

Originally Posted by iroczracer07
Have you checked your intake manifold gaskets for leaks?
I have not, how do I go by doing that?
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Old Apr 24, 2012 | 07:03 PM
  #16  
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Car: 1989 Camaro
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Transmission: 700r4
Axle/Gears: I'm working on it,lol.
Re: Rough Idle

A lot of people use carb cleaner and spray it around the intake to cylinder heads, around injectors, vacuum lines, and the power brake booster. The idle will smooth out real quick once you hit a spot with a leak and then die down.
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Old Apr 24, 2012 | 07:49 PM
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Re: Rough Idle

Originally Posted by 11ellswray
bosh-3 type, where do most people buy these? because im searching summit and so far no good, and will these work for a earlier 350 car?
If you haven't purchased injectors yet and you are planning on replacing yours, we can help you. We have an extremely large inventory of various size bosch lll's. All tgo members receive a 10% discount. If you decide to purchase a set you can go to our website and at checkout just type in promo code tg11.
If you have any questions feel free to call us. Make sure you mention that you are a tgo member.

www.southbayfuelinjectors.com
516-442-4707
516-492-6504
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Old Apr 24, 2012 | 09:49 PM
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Car: 1989 Camaro
Engine: 350 but it's torn down right now.
Transmission: 700r4
Axle/Gears: I'm working on it,lol.
Re: Rough Idle

Originally Posted by southbay08
If you haven't purchased injectors yet and you are planning on replacing yours, we can help you. We have an extremely large inventory of various size bosch lll's. All tgo members receive a 10% discount. If you decide to purchase a set you can go to our website and at checkout just type in promo code tg11.
If you have any questions feel free to call us. Make sure you mention that you are a tgo member.

www.southbayfuelinjectors.com
516-442-4707
516-492-6504
That's pretty sweet
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Old Apr 25, 2012 | 07:22 PM
  #19  
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Car: 1986 Camaro IROC Z28
Engine: 5.0L 305 TPI
Re: Rough Idle

Originally Posted by iroczracer07
A lot of people use carb cleaner and spray it around the intake to cylinder heads, around injectors, vacuum lines, and the power brake booster. The idle will smooth out real quick once you hit a spot with a leak and then die down.
Alright, I will give that a shot. It'll be a little over a week. I have exams coming up so I don't have a lot of time for it. I will post an update on what happens though.
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Old Apr 25, 2012 | 07:28 PM
  #20  
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Car: 1986 Camaro IROC Z28
Engine: 5.0L 305 TPI
Re: Rough Idle

Originally Posted by 305sbc
Next step is to pull the rail up with the injectors still in it and do the test again.
You should be able to see if fuel leaks from the injectors and from which ones.
Sometimes the injectors still need to be warm for them to leak during the test.
At that point you get a good idea about what is going on and what exactly is wrong and may need replaced. Then you go from there.

If injectors are bad, then most people replace them with the newer style Bosh-3 type.
Am I looking to get the Bosch lll 42lb or Bosch lll 36lb injectors? I am assuming 36lb because my car runs at 35psi ad then 45psi when the vacuum line is off.
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