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07-24-2014, 03:15 PM
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#1 |
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Registered User
Join Date: Jul 2007
Location: Fall River California
Posts: 2,026
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Tach pulses at idle
I noticed my engine stumbling at idle, I looked at my tach and the needle pulses or bounces while the engine idles. The tack jumps about 20 rpm for just a partial second then does it again about every 2 to 3 seconds. What could cause this? A bad plug? Plug wire? I checked all the wires and they seem fine. The engine is a 350 with electronic distributor. I've never notice this happening before. Thanks for any suggestions!
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07-24-2014, 03:17 PM
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#2 | ||||
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"I ain't nobody, dork."
Join Date: Sep 2007
Location: Whidbey Island, Washington
Posts: 8,971
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Re: Tach pulses at idle
Stock Tach? Or aftermarket?
Gary
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07-24-2014, 03:21 PM
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#3 | |
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Registered User
Join Date: Jul 2007
Location: Fall River California
Posts: 2,026
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Re: Tach pulses at idle
Quote:
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07-25-2014, 09:04 AM
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#4 |
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Registered User
Join Date: Feb 2012
Location: Smyrna TN
Posts: 1,153
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Re: Tach pulses at idle
Are you running a stock intake manifold or aftermarket? My big block has always done it, even after engine and carb rebuild. I went back with the same Edelbrock intake after the engine build. I've always thought the intake is the culprit but didn't replace it in the shuffle of everything else being rebuilt.
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07-25-2014, 10:10 AM
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#5 |
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Registered User
Join Date: Jul 2012
Location: Rosenberg, Texas
Posts: 3,506
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Re: Tach pulses at idle
You could always pull one spark plug wire at a time while it's running. If you don't notice a drop in rpm, you've got a dead cylinder. Could be the wire, a plug, the cap...
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-Duane C/10 Club Texas member 1971 Chevy C10 "Brutus" SWB Fleetside 2016 6.0L (L96) 6L90E (driver/project) 1965 Pontiac GTO "Royal Goat" 400/TH400 w/AC (my baby) |
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07-25-2014, 10:39 AM
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#6 |
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Registered User
Join Date: Jan 2014
Location: Tulsa, OK
Posts: 360
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Re: Tach pulses at idle
My truck was doing this last week. I found a spark plug with cracked porcelain. I replaced the plug and it idles smoothly now.
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-Jason USN Retired |
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09-03-2014, 11:24 AM
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#7 |
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Registered User
Join Date: Jul 2007
Location: Fall River California
Posts: 2,026
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Re: Tach pulses at idle
I ended up replacing plug wires, cap, rotor and plugs. Tach and truck are running much smoother.
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