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Author
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Topic: Why is my carb motor running rough?
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BCINGUU
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Member # 2397
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posted
 
 
My 67 stang with its original 289 motor is running rough and stalling at idle. It seems to be running very rich. I just removed the EGR and didn't seal the intake ports very well, so it's sucking air through those ports.
Don't know much about carb motors, but on an EFI system I know this situation would cause more air to enter the intake than what the MAF is measuring, thereby causing the ECU to spray less fuel than needed. This may result in a way lean condition possibly resulting on a lean misfire.
But on a carb motor? I'm guessing I need to seal up those EGR ports better or get some kind of eliminator. Does anybody know if there is such a thing? Who has eliminated their EGR and how did you do it? Is the carb tuned for the EGR and now not spraying enough fuel, just like in the EFI world?
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93 Cobra #4563 347ci 12.0@118 505rwhp 524tq
90 GT "Saleen Cobra" style convertible 347ci
67 GT "Eleanor" style coupe 347ci
Posts: 1425 | From: San Jose, CA | Registered: Jan 2003
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FasterDamnit
Bad Attitude
Member # 442
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posted
For the Carb to meter fuel into the motor, the air has to go THRU the carb. Any vacuum leak will cause your symptoms.
Posts: 2971 | From: NorCal | Registered: Sep 2001
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JohnB
Tech Moderator
Member # 969
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posted
Re-seal the intake, use block-off tabs on the intake manifold gaskets and a block-off plate for the EGR port. Yes, your vaccum leak is causing the rich condition. And get rid of the 2bbl already!! ![[Big Grin]](biggrin.gif)
I've got a intake and carb ready to go here if you're interested. Weiand intake and a near-new Holley carb.
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1965 Shelby Cobra
1993 Cobra
2012 F150 Raptor
2020 GT500
Posts: 6523 | From: Orlando FL/Redding CA | Registered: Mar 2002
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BCINGUU
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Member # 2397
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posted
10-4 guys, thanks for the sanity check.
How the hell did you know I had a 2bbl John? ;D
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93 Cobra #4563 347ci 12.0@118 505rwhp 524tq
90 GT "Saleen Cobra" style convertible 347ci
67 GT "Eleanor" style coupe 347ci
Posts: 1425 | From: San Jose, CA | Registered: Jan 2003
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BCINGUU
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Member # 2397
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posted
dp
[ July 06, 2007, 12:10 AM: Message edited by: BCINGUU ]
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93 Cobra #4563 347ci 12.0@118 505rwhp 524tq
90 GT "Saleen Cobra" style convertible 347ci
67 GT "Eleanor" style coupe 347ci
Posts: 1425 | From: San Jose, CA | Registered: Jan 2003
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MustangNate
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Member # 4559
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posted
Because you said you had the original 289. ![[Razz]](tongue.gif)
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1989 Mustang LX Vert, 5.0 Auto
Posts: 1032 | From: Chico | Registered: May 2004
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BCINGUU
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Member # 2397
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posted
Ah, the process of deduction, Watson.
My problem is resolved, thanks again gentlemen.
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93 Cobra #4563 347ci 12.0@118 505rwhp 524tq
90 GT "Saleen Cobra" style convertible 347ci
67 GT "Eleanor" style coupe 347ci
Posts: 1425 | From: San Jose, CA | Registered: Jan 2003
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FasterDamnit
Bad Attitude
Member # 442
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posted
quote:
Originally posted by MustangNate:
Because you said you had the original 289.
Really? My original 289 was a 4 barrel.
Posts: 2971 | From: NorCal | Registered: Sep 2001
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BCINGUU
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Member # 2397
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posted
I think they had different options. Mine is indeed 2 bbl.
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93 Cobra #4563 347ci 12.0@118 505rwhp 524tq
90 GT "Saleen Cobra" style convertible 347ci
67 GT "Eleanor" style coupe 347ci
Posts: 1425 | From: San Jose, CA | Registered: Jan 2003
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FasterDamnit
Bad Attitude
Member # 442
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posted
quote:
Originally posted by BCINGUU:
I think they had different options. Mine is indeed 2 bbl.
A code vs. C code.
Posts: 2971 | From: NorCal | Registered: Sep 2001
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90lxfoxbody
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Member # 6947
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posted
67s had egr valves ?
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Owner Of All Out Performance
Ya I own that Cobra
Old setup whipple and jug 9.37 155
New twins hoping for 8.50s at 165
Posts: 588 | From: fresno ca | Registered: Jul 2006
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BCINGUU
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Member # 2397
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posted
Yeah, and a smog pump too. Guess they started the emission stuff early.
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93 Cobra #4563 347ci 12.0@118 505rwhp 524tq
90 GT "Saleen Cobra" style convertible 347ci
67 GT "Eleanor" style coupe 347ci
Posts: 1425 | From: San Jose, CA | Registered: Jan 2003
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2stangs69-91
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Member # 1951
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posted
first off a vacuum leak on a carb car will NOT cause a rich condition. I agree also on swaping on a 4barrel carb. good luck. But a vacuum leak will cause your car to die at idle. Good luck.
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69 Mustang on hold
1991 LX hatch getting a make over
1994 F150 4X4 351
2006 Yamaha V-max 1200 Modded
Posts: 3711 | From: Redding | Registered: Oct 2002
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BCINGUU
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Member # 2397
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posted
I had a big vac leak and when I plugged it everything was fine. I think the car went way too lean, resulting in a lean misfire. Not a rich condition but a lot of unburnt fuel getting out.
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93 Cobra #4563 347ci 12.0@118 505rwhp 524tq
90 GT "Saleen Cobra" style convertible 347ci
67 GT "Eleanor" style coupe 347ci
Posts: 1425 | From: San Jose, CA | Registered: Jan 2003
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