Weird grounding problem?
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Senior User
Joined: Jun 2001
Posts: 107
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From: Pater, Maine
Weird grounding problem?
Specs: 1985 F-150 4.9L C6
The other day while I was timing the truck I noticed the ground cable on the battery (new battery) was loose. As I was pulling the timing light connector off the ground cable the ground cable almost came off the battery but was still touching enough to keep the engine running.
Now here is the real kicker: The truck has always ran kinda rough. It has this miss during idle that I just haven't been able to track down. But when the ground cable almost pulled of the battery, the idle speed came up just a bit (maybe another 100 rpm's) and it stopped missing!!!!! The idle is set to 750 and I can usually get it to miss to just over 1200rpm's. The idle didn't jump dramatically or anything like that. It just seemed to have stopped misfiring and ran a whole lot better. What the heck!??!
The ground cable is old but isn't frayed or corroded and the battery is new. And neither the + or - posts are corroded. The posts have been cleaned.
Do I have a main/engine ground problem? I'm totally clueless. Usually the worse the ground the more it will adversely affect the engine, electronics, gauges, etc...
The other day while I was timing the truck I noticed the ground cable on the battery (new battery) was loose. As I was pulling the timing light connector off the ground cable the ground cable almost came off the battery but was still touching enough to keep the engine running.
Now here is the real kicker: The truck has always ran kinda rough. It has this miss during idle that I just haven't been able to track down. But when the ground cable almost pulled of the battery, the idle speed came up just a bit (maybe another 100 rpm's) and it stopped missing!!!!! The idle is set to 750 and I can usually get it to miss to just over 1200rpm's. The idle didn't jump dramatically or anything like that. It just seemed to have stopped misfiring and ran a whole lot better. What the heck!??!
The ground cable is old but isn't frayed or corroded and the battery is new. And neither the + or - posts are corroded. The posts have been cleaned.
Do I have a main/engine ground problem? I'm totally clueless. Usually the worse the ground the more it will adversely affect the engine, electronics, gauges, etc...
Posting Guru
Joined: Mar 2002
Posts: 1,217
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From: Yelm Washington usa
Weird grounding problem?
I had to run a ground wire from the batt to the block and from the frame to the block and from the frame to the body. By doing that it ran better and gave me more juice in the cab.
dj
dj
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Joined: Jan 2000
Posts: 5,860
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From: Metro Detroit (Redford)
Weird grounding problem?
I figure (this is a guess) the loose ground was causing it to run poor and when the cable almost came off it actually improved the connection. I would clean up the contacts and mount the cable tight.
Once when I had some work done on my truck and the next morning I fired her up and immediately all the lights died--everything. I went under the hood and, sure enough, I could wiggle the ground battery cable. Tightened it and everything worked fine again and ever since.
INLINE SIX POWER!
300 Cubic Inches of Low RPM Truck Torque! And twin-I-beams too!
"Drive a stick young man! There'll be time for automatics when you're old and unable."
Once when I had some work done on my truck and the next morning I fired her up and immediately all the lights died--everything. I went under the hood and, sure enough, I could wiggle the ground battery cable. Tightened it and everything worked fine again and ever since.
INLINE SIX POWER!
300 Cubic Inches of Low RPM Truck Torque! And twin-I-beams too!
"Drive a stick young man! There'll be time for automatics when you're old and unable."
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