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PostPosted: Wed Apr 12, 2023 12:47 pm 
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4 BBL ''Hyper-Pak''

Joined: Sat Jul 23, 2022 1:21 pm
Posts: 48
Car Model: Dart
Ok, bad news - After I adjusted the valves and let it run in the garage yesterday I decided to take is for a quick test drive to go get some gas (91 octane). By the time I got down to the gas station it started running rough again and wanted to die. I did try opening the idle mixtures and that did not help any. Again, under power it is smooth with no pause or hesitation. So, I am thinking again that maybe the throttle body has some debris in it. I am thinking of pulling the carb back off and sonic cleaning the throttle body to get any debris/deposits that are in there out.

I am also going to re-time it and try to get it down from the 12 degrees it is at right now.


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PostPosted: Thu Apr 13, 2023 6:34 am 
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EFI Slant 6

Joined: Mon May 26, 2014 4:02 pm
Posts: 418
Location: Vermont
Car Model: Slant Six M37
cmann wrote:
Ok, bad news - So, I am thinking again that maybe the throttle body has some debris in it. I am thinking of pulling the carb back off and sonic cleaning the throttle body to get any debris/deposits that are in there out.

I am also going to re-time it and try to get it down from the 12 degrees it is at right now.



If the carb had debris in the passages then I would doubt that it would run smoothly when cold.

It sounds like this issue is now showing up once the engine has warmed up. Is that correct?


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PostPosted: Thu Apr 13, 2023 6:42 am 
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4 BBL ''Hyper-Pak''

Joined: Sat Jul 23, 2022 1:21 pm
Posts: 48
Car Model: Dart
Yes, that is correct. Once it is at running temperature is when it wants to start to die when idling. Again, past idle it runs great.


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PostPosted: Thu Apr 13, 2023 9:33 am 
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Turbo EFI
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Joined: Mon Aug 02, 2010 7:36 am
Posts: 1200
Location: Rome, GA
Car Model: 1963 Dart 270, 1980 D150
My son's D100 did the same thing. Debris in the idle circuit.

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PostPosted: Thu Apr 13, 2023 11:54 am 
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Joined: Mon Oct 21, 2002 11:08 am
Posts: 16510
Location: Blacksburg, VA
Car Model:
Pull idle mix screws and blow out with carb cleaner?
Lou

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PostPosted: Thu Apr 13, 2023 3:03 pm 
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Joined: Thu Oct 31, 2002 5:39 pm
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Location: North America
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cmann wrote:
a quick test drive to go get some gas (91 octane)
Why are you buying high-test gasoline for this car? From what you've described of the build, it shouldn't be necessary. And if it's not necessary, it's not beneficial—just a waste of dollars. If you have to run 91 or else the engine pings…take out the excessive base timing; get it back around 5° and that should resolve the pinging.

Sounds like there is (still) trash in your carb's idle circuit and/or air bleeds.

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PostPosted: Thu Apr 13, 2023 3:05 pm 
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Jase wrote:
If the carb had debris in the passages then I would doubt that it would run smoothly when cold.
If the carb has trash in the idle circuit, you often won't see a symptom until the engine is warm enough for the choke to come off and the fast-idle cam to swing out of the way.

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PostPosted: Thu Apr 13, 2023 7:29 pm 
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4 BBL ''Hyper-Pak''

Joined: Sat Jul 23, 2022 1:21 pm
Posts: 48
Car Model: Dart
Thank you Dan for your reply/input. Yes, I plan on taking the throttle body off and cleaning. The engine is not pinging. I plan on bringing the timing down. Just thought I would run some good gas in it while tuning. I will keep you posted on the progress/response after cleaning the throttle body.


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PostPosted: Thu Apr 13, 2023 11:57 pm 
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cmann wrote:
I plan on taking the throttle body off and cleaning.
Good, but that might not be where the trash is located.

Quote:
The engine is not pinging. Just thought I would run some good gas in it while tuning
It is a complete mistake to think higher-octane gasoline is better. It is not. Tune the car on the kind of gasoline you'll usually be running in it.

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