Carburetors Carb discussion and questions. Upgrading your Third Gen's carburetor, swapping TBI to carburetor, or TPI to carburetor? Need LG4 or H.O. info? Post it here.

Carb help please

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Old Oct 28, 2012 | 04:17 PM
  #1  
ttopkindaguy's Avatar
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Joined: Oct 2012
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From: Pennsylvania
Car: 1987 Trans Am
Engine: Chevy 350 c.i.
Transmission: 700r4 Automatic w/Shift kit
Axle/Gears: Posi rear w/383 gears
Carb help please

Hey guys, I'm new to thirdgen.org, and I need some help with my car.

I recently bought a 1987 Trans Am with a 350, carbureted (Quadrajet). Automatic 700r4 tranny with a shift kit.

Here are the problems:

1. When I pull out from a stop sign or light (Whether engine is cold or up to temp, doesn't matter), The car wants to shut off, die. I either have to pull out slow, or, I can hit the gas, get off the gas, and back on and then it will go. It is idling right around 800 rpm.

2. When it is in park, or neutral, and i rev my engine up AT ALL, after i get off, the car drops to really low rpms (300), and then it starts to shake violently.

Please help guys, sorry for the long post
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Old Oct 28, 2012 | 04:20 PM
  #2  
ttopkindaguy's Avatar
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From: Pennsylvania
Car: 1987 Trans Am
Engine: Chevy 350 c.i.
Transmission: 700r4 Automatic w/Shift kit
Axle/Gears: Posi rear w/383 gears
Re: Carb help please

Also, car has like no power. Feels very slow.....
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Old Oct 28, 2012 | 04:24 PM
  #3  
hdavis2005's Avatar
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Posts: 50
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From: Eastern NC
Car: 1992 Camaro RS
Engine: 3.1 MPFI to 305 carb
Transmission: 700R4
Axle/Gears: 323
Re: Carb help please

Have you checked the fuel filter? You may have 2. One underneath the car left side near the rear wheel and one in the carb.
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Old Oct 28, 2012 | 04:29 PM
  #4  
ttopkindaguy's Avatar
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Joined: Oct 2012
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From: Pennsylvania
Car: 1987 Trans Am
Engine: Chevy 350 c.i.
Transmission: 700r4 Automatic w/Shift kit
Axle/Gears: Posi rear w/383 gears
Re: Carb help please

Yeah I have a new one just didn't replace it yet... couldn't find it. But it feels like maybe the float is sticking maybe???
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Old Oct 28, 2012 | 04:39 PM
  #5  
hdavis2005's Avatar
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Joined: Jun 2012
Posts: 50
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From: Eastern NC
Car: 1992 Camaro RS
Engine: 3.1 MPFI to 305 carb
Transmission: 700R4
Axle/Gears: 323
Re: Carb help please

if float sticks it will be flooding. Changing those filters should be your first step. I have rebuilt a lot of these and trash is a carb's number 1 enemy.

Last edited by hdavis2005; Nov 8, 2012 at 09:56 PM.
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Old Oct 28, 2012 | 04:42 PM
  #6  
ttopkindaguy's Avatar
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From: Pennsylvania
Car: 1987 Trans Am
Engine: Chevy 350 c.i.
Transmission: 700r4 Automatic w/Shift kit
Axle/Gears: Posi rear w/383 gears
Re: Carb help please

Alright I'll do that when I get a chance. We are getting hit by a hurricane for the next day or 2 lol so it might not get done soon but thanks. Any ideas about the shaking? Same thing?
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Old Oct 28, 2012 | 05:06 PM
  #7  
hdavis2005's Avatar
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Joined: Jun 2012
Posts: 50
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From: Eastern NC
Car: 1992 Camaro RS
Engine: 3.1 MPFI to 305 carb
Transmission: 700R4
Axle/Gears: 323
Re: Carb help please

I would think so. Change the one at carb first. Is it idleing Rough?
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Old Oct 28, 2012 | 05:07 PM
  #8  
hdavis2005's Avatar
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Joined: Jun 2012
Posts: 50
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From: Eastern NC
Car: 1992 Camaro RS
Engine: 3.1 MPFI to 305 carb
Transmission: 700R4
Axle/Gears: 323
Re: Carb help please

Be safe in the storm
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Old Oct 28, 2012 | 08:45 PM
  #9  
ttopkindaguy's Avatar
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From: Pennsylvania
Car: 1987 Trans Am
Engine: Chevy 350 c.i.
Transmission: 700r4 Automatic w/Shift kit
Axle/Gears: Posi rear w/383 gears
Re: Carb help please

It all depends. Usually in the morning, a cold start, it won't idle rough. If I start it up in the afternoon, say around 3-4 o'clock, it idles rough until it warms up.
And thanks
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Old Oct 29, 2012 | 08:39 AM
  #10  
afremont's Avatar
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Car: 90 IROC
Engine: 5.7 TPI
Transmission: 4L60
Axle/Gears: 3.23
Re: Carb help please

On top of what others said, make sure your distributor isn't loose and able to turn. Check your timing. A bad accelerator pump in the carb could explain why you have trouble accelerating normally, but so could an overall lean condition in the carb or bad timing. What kind of distributor are you running, and does it have a real vacuum advance mechanism?
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Old Oct 29, 2012 | 11:24 AM
  #11  
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Joined: Sep 2004
Posts: 719
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From: N. Ky
Car: 86 T/A - 70 Z28/RS
Engine: Broke - 350
Transmission: 700R4 - M22
Axle/Gears: G80, 2.73 - ZQ9 G80 4.10
Re: Carb help please

Originally Posted by afremont
On top of what others said, make sure your distributor isn't loose and able to turn. Check your timing. A bad accelerator pump in the carb could explain why you have trouble accelerating normally, but so could an overall lean condition in the carb or bad timing. What kind of distributor are you running, and does it have a real vacuum advance mechanism?
+1
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Old Oct 31, 2012 | 06:32 AM
  #12  
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From: St. Cloud, MN
Car: 1984 Trans Am
Engine: LS1383 in work
Transmission: Magnum F - to be installed
Axle/Gears: Zexel Torsen 3.73, 28-spline mosers
Re: Carb help please

Unles it's changed, it should be a CC Qjet. However, being an 87, I'm pretty sure those were all fuel injected. In which case, it's not going to be a CCqet, though it might be a vac-advance version.
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Old Oct 31, 2012 | 07:34 AM
  #13  
bestracing's Avatar
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From: N. Ky
Car: 86 T/A - 70 Z28/RS
Engine: Broke - 350
Transmission: 700R4 - M22
Axle/Gears: G80, 2.73 - ZQ9 G80 4.10
Re: Carb help please

350 motors were TPI only so I'm sure he's either ditched the TPI or swapped a carb'ed 350 into the car.

With aftermarket distributors you can get mechanical advance only. These are mostly for racing where timing advanced during cruise speeds are irrelevant.

Also I have seen people use cc-distributors as on non-ECM motors and wonder why their motor isn't running right. You can't really assume anything over a message board and no offense to the OP, he's just trying to understand the whole situation.
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Old Oct 31, 2012 | 07:34 AM
  #14  
Edwardgp's Avatar
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From: Washington State
Car: 1983 BB 1995 Z28 Camaro's
Engine: 454-350
Transmission: TH350-4l60e
Axle/Gears: 373 posi-Stock
Re: Carb help please

Accelerator pump in carburetor, fuel filters, tune up??
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Old Oct 31, 2012 | 10:21 PM
  #15  
ttopkindaguy's Avatar
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Joined: Oct 2012
Posts: 20
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From: Pennsylvania
Car: 1987 Trans Am
Engine: Chevy 350 c.i.
Transmission: 700r4 Automatic w/Shift kit
Axle/Gears: Posi rear w/383 gears
Re: Carb help please

yes, the motor was swapped from a TPI 305 to a Qjet carbureted 350
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Old Nov 1, 2012 | 09:03 AM
  #16  
naf's Avatar
naf
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From: Lexington, SC
Car: 1987 SC/1985 TA
Engine: 350/vortec/fitech
Transmission: T56
Axle/Gears: 3.27 9-bolt
Re: Carb help please

Tune up all of your ignition components: replace the plugs, wires, cap and coil if you don't KNOW they're new within the last 5000 miles.

If you've got a distributor without the vacuum advance can on the side, replace it with one that does. See where your base timing at idle is (with vac line disconnected) and verify that the timing advance is working properly. Exactly how much is not as important as making sure that it advances as the throttle is increased and maxes out around 3000 or so rpm.

ONLY after all of the ignition stuff is KNOWN good, start looking at the carburetor. It could likely use a good rebuild. Especially if it's crudded up and no one knows how long since it's been cleaned out real good.
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Old Nov 2, 2012 | 05:06 AM
  #17  
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From: Los angeles
Car: 92 Firebird Formula
Engine: 5.0 V8
Re: Carb help please

try changing the distributor cap and coil happen to me before
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Old Nov 7, 2012 | 08:21 PM
  #18  
ttopkindaguy's Avatar
Thread Starter
Junior Member
 
Joined: Oct 2012
Posts: 20
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From: Pennsylvania
Car: 1987 Trans Am
Engine: Chevy 350 c.i.
Transmission: 700r4 Automatic w/Shift kit
Axle/Gears: Posi rear w/383 gears
Re: Carb help please

Is there a specific cap and coil I should get?
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Old Nov 8, 2012 | 04:26 AM
  #19  
Ozz1967's Avatar
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20 Year Member
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Joined: Dec 2005
Posts: 4,795
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From: St. Cloud, MN
Car: 1984 Trans Am
Engine: LS1383 in work
Transmission: Magnum F - to be installed
Axle/Gears: Zexel Torsen 3.73, 28-spline mosers
Re: Carb help please

Originally Posted by ttopkindaguy
Is there a specific cap and coil I should get?
No, but if you can afford to, you might as well go with MSD. I'm assuming you have the "coil-in-cap" style dizzy.
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Old Nov 8, 2012 | 06:37 AM
  #20  
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naf
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From: Lexington, SC
Car: 1987 SC/1985 TA
Engine: 350/vortec/fitech
Transmission: T56
Axle/Gears: 3.27 9-bolt
Re: Carb help please

Standard parts store stuff is fine. I'd stay away from Accel though, I've had fitment issues with them where they rocked even after clipped down.
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Old Nov 8, 2012 | 08:40 AM
  #21  
bestracing's Avatar
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Joined: Sep 2004
Posts: 719
Likes: 0
From: N. Ky
Car: 86 T/A - 70 Z28/RS
Engine: Broke - 350
Transmission: 700R4 - M22
Axle/Gears: G80, 2.73 - ZQ9 G80 4.10
Re: Carb help please

I have seen where the center contact button inside the standard parts store dist. have high resistance leading to spark scatter problems at higher rpm's (>3K). MSD has one of the lowest resistance center buttons on the market and I highly recommend using them.
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Old Nov 8, 2012 | 09:28 PM
  #22  
ttopkindaguy's Avatar
Thread Starter
Junior Member
 
Joined: Oct 2012
Posts: 20
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From: Pennsylvania
Car: 1987 Trans Am
Engine: Chevy 350 c.i.
Transmission: 700r4 Automatic w/Shift kit
Axle/Gears: Posi rear w/383 gears
Re: Carb help please

Thanks, all.. One more question. Would anyone be able to tell me the 'part number' or 'code' of the carburetor? It is the stock quadrajet but i don't see a number on it anywhere.
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Old Nov 8, 2012 | 09:53 PM
  #23  
hdavis2005's Avatar
Junior Member
 
Joined: Jun 2012
Posts: 50
Likes: 1
From: Eastern NC
Car: 1992 Camaro RS
Engine: 3.1 MPFI to 305 carb
Transmission: 700R4
Axle/Gears: 323
Re: Carb help please

The carb numbers are stamped on the carb body. Facing carb they are on the right side near the back.
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Old Nov 10, 2012 | 03:32 PM
  #24  
ttopkindaguy's Avatar
Thread Starter
Junior Member
 
Joined: Oct 2012
Posts: 20
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From: Pennsylvania
Car: 1987 Trans Am
Engine: Chevy 350 c.i.
Transmission: 700r4 Automatic w/Shift kit
Axle/Gears: Posi rear w/383 gears
Re: Carb help please

Once again, thanks everyone! The main solution, I figured it out: The catalytic converter was screwed. I cut that off, now it is loud as hell, seeing as it is straight piped, and acceleration is 10000x better.
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