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 73 Grand Prix 455 stalling
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rock47
Tribal Scout

USA
1 Posts

Posted - 09 Aug 2014 :  10:05:21 AM  Show Profile  Reply with Quote
My 73 Grand Prix is a factory 455 that I have owned fro 40 years. There are 95,000 miles actual miles on the odometer.
I had trouble with the pump at my regular station so the attendant moved me to a different pump and pumped the gas for me. After driving about 40 miles the car began to stall and I would slow down and shift to neutral and the engine would pick up and run for a time and stall again. I suspected bad gas or ethanol.
I changed the fuel filter and air cleaner and filled up with 91 octane and added some octane booster. I ran that tank full out and so no change. I refilled with 91 octane and tried again, same results.
Can anyone give me a credible explanation or fix for it?
Thanks, Roger

Roger Santi

Mr. P-Body
Running Bear

USA
2258 Posts

Posted - 09 Aug 2014 :  11:42:25 AM  Show Profile  Visit Mr. P-Body's Homepage  Reply with Quote


Sounds like carb rebuild is in order. Replace the float while you're in there.

Jim
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cortcomp
Coyote

USA
5339 Posts

Posted - 09 Aug 2014 :  6:41:08 PM  Show Profile  Visit cortcomp's Homepage  Reply with Quote
I would also check the rubber fuel line connections to make sure you're not sucking air somewhere.
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Blued and Painted
Chief PONTIAC

USA
3409 Posts

Posted - 10 Aug 2014 :  12:44:47 AM  Show Profile  Reply with Quote
Hard to tell by the description. Do you think it's flooding with black smoke out the exhaust, or running out of fuel. Fuel pump or needs a set of breaker points.


Bull Nose Formula/ 461/ Q-Jet/
TH400/ 3.08 8.5 / R44TS.
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Phil
The Great White Buffalo

USA
7223 Posts

Posted - 10 Aug 2014 :  7:53:40 PM  Show Profile  Reply with Quote
Dirt in carb since this happened suddenly. I've had this problem many times. Take the carb off, set it on a table, take the top off and make yourself comfortable.. Clean out the carb thoroughly including all of the tiny passages (use wire strands where needed). Blow out with compressed air when done. Reassemble with updated Cliff parts compatible with ethanol also highly recommended.

Bowties are for Pee-wee Herman. "Chevy": even the name sounds cheap, but not as cheap as your Pontiac will be with an LS transplant.

Edited by - Phil on 10 Aug 2014 7:55:49 PM
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67drake
Sitting Duck

Azerbaijan
1501 Posts

Posted - 10 Aug 2014 :  8:18:14 PM  Show Profile  Reply with Quote
I'll just throw this out there.
When you say "and still no change" after you filled up a few more times,do you mean it ran OK for a while,then started running bad after you ran the tank down some? Or did it still run bad even right after the fresh fill up?

I took a trip out to SD over the winter and the same thing happened to me with my Suburban. EVERY time I got to about 1/2 a tank the truck would run rough and then stall going down the highway. It would always run great right after I filled the tank though. This started after I filled up at some out of the way "mom and pop" type station in the middle of nowhere that may have had old or water contaminated gas.
I put a can of "Heet" in it,and just kept the tank topped off till I got home. No problems when I did this.

I don't disagree with the carb issue,but maybe a case of water in the tank that needs to work it's way out,or be drained.



71' GTO Original 400 M20 3.23 posi
13.95@102.1 MPH on street tires

Edited by - 67drake on 10 Aug 2014 8:25:34 PM
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Phil
The Great White Buffalo

USA
7223 Posts

Posted - 10 Aug 2014 :  8:53:57 PM  Show Profile  Reply with Quote
If that's the case the sock may be clogged too.

Bowties are for Pee-wee Herman. "Chevy": even the name sounds cheap, but not as cheap as your Pontiac will be with an LS transplant.
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