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09-16-2024, 08:26 PM
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#1 |
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Registered User
Join Date: Jun 2017
Location: Mentor, OH
Posts: 137
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Rough idle and takeoff 250 inline
Good evening....
My '68 GMC has an inline 250. It's been running beautifully all summer, including this past Saturday when I took it on a 400 mile, all highway trip to a show. Yesterday I went to go for a ride and now it's idling rough and is rough on takeoff with an occasional backfire. Once up to speed it still runs fine. I changed the points tonight since they looked pretty bad (after only a year) and it didn't help. Tomorrow I'm changing the plugs. What else could it possibly be? Last year I changed everything... Plugs, wires, cap, rotor, points, condenser, coil, carb rebuilt, timed, etc... Thanks! Last edited by 68gmcdude; 09-16-2024 at 09:53 PM. |
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Yesterday, 07:20 AM
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#2 |
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State of Confusion!
  
Join Date: Jul 2002
Location: Gulfport, MS USA
Posts: 46,947
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Re: Rough idle and takeoff 250 inline
Check/CHange/claen your fuel filter. You may mav gotten a piece of crude in it that's partially clogging things.
__________________
Bill 1970 Chevy Custom/10 LWB Fleetside 2010 Toyota Tacoma PreRunner SR5 Double Cab - DD Member of Louisiana Classic Truck Club (LCTC) Bill's Gallery Life isn't tied with a bow, but it's still a gift. Live simply. Love generously. Care deeply. Speak kindly. Leave the rest to God! |
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Yesterday, 07:59 AM
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#3 | |
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Registered User
Join Date: Jun 2017
Location: Mentor, OH
Posts: 137
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Re: Rough idle and takeoff 250 inline
Quote:
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Yesterday, 09:58 AM
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#4 |
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Registered User
Join Date: Dec 2023
Location: Rural California
Posts: 24
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Re: Rough idle and takeoff 250 inline
Check for a vacuum leak then check the timing.
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Yesterday, 10:58 AM
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#5 | |
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Registered User
Join Date: Jun 2017
Location: Mentor, OH
Posts: 137
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Re: Rough idle and takeoff 250 inline
Quote:
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Yesterday, 03:44 PM
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#6 |
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Post Whore
Join Date: Feb 2016
Location: Portland Oregon
Posts: 11,201
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Re: Rough idle and takeoff 250 inline
I would break out my vacuum guage and see what it told me. If your not familiar with using one here is a basic primer. The vacuum guage should point you in the right direction in your troubleshooting.
There are numerous other articles as well as videos to help on the interweb. https://www.onallcylinders.com/2015/...gine-problems/ Good luck. I hope it turns out to be an easy fix.
__________________
Thanks to Bob and Jeanie and everyone else at Superior Performance for all their great help.  RIP Bob Parks. 1967 Burban (the WMB),1988 S10 Blazer (the Stink10 II),1969 GTO (the Goat), 1970 Javelin, 1952 F2 Ford OHC six 4X4, 29 Model A, 72 Firebird (the DBP Bird). 85 Alfa Romeo If it breaks I didn't want it in the first place The WMB repair thread http://67-72chevytrucks.com/vboard/s...d.php?t=698377 |
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Yesterday, 08:41 PM
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#7 |
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Registered User
Join Date: Jun 2017
Location: Mentor, OH
Posts: 137
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Re: Rough idle and takeoff 250 inline
I have changed the points, condenser and spark plugs. Point were set to. 019 gap according to the manual. Timing was off and is good now. Seems to be idling better but have yet to drive it. Hooked up a dwell meter and it is only reading 24. Should be 31-34 according to the manual. I keep reading that the dwell/ points should be set with the motor cranking, not with a feeler gauge. I have never done this. How do you do this by yourself? And how do you keep the motor cranking while adjusting the dwell / points?.... Help? Thanks!
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