460 with timing issues
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460 with timing issues
89 f-350 dually has a 460 with an auto tranny.
I put new spark plugs, dist cap, rotor, and plug wires but I still thought the timing was off in my truck so I went to set it. I was right it was at about 31*. I took the plug off the module and took the wire to the computer out and plugged it back up. I checked the timing again before I moved the dist and it was at 10* now. So there's no need to move the dist. I put the wire back together in the module and hooked it back up. I started looking at the vacum lines and found one loose, It moved the timing to about 12* but as soon as I shut the truck off and started it back up the timing went straight to 30* or so.
Does anyone have any ideas on whats going on??
Thanks.
I put new spark plugs, dist cap, rotor, and plug wires but I still thought the timing was off in my truck so I went to set it. I was right it was at about 31*. I took the plug off the module and took the wire to the computer out and plugged it back up. I checked the timing again before I moved the dist and it was at 10* now. So there's no need to move the dist. I put the wire back together in the module and hooked it back up. I started looking at the vacum lines and found one loose, It moved the timing to about 12* but as soon as I shut the truck off and started it back up the timing went straight to 30* or so.
Does anyone have any ideas on whats going on??
Thanks.
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From: Pryor
It was 31 while it was running? And then 10 when it was stopped? It should be at about 36 degrees or so TOTAL timing by 3000 RPM's. That will include both mechanical and vacuum advance. Initial timing should be about 14 degrees. If you could explain the procedures you went through while checking these it would help a bit.
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- The first time I checked it : running at idle, module untouched it was 31*
- Then I shut it off, took off the harness from the module, and unpluged the wire to the computer.
- I plugged the harness back up to the module minus one wire.
- Checked timing again : running at idle, timing was about 10*
- I shut it off, hooked the wire back to the module, started it, and the timing jumped back to 31*
- Still running, I started looking for the vacum lines, moved a couple and timing went to about 12* but as soon as I stopped the motor and started it back the timing went back to 31*
- Then I shut it off, took off the harness from the module, and unpluged the wire to the computer.
- I plugged the harness back up to the module minus one wire.
- Checked timing again : running at idle, timing was about 10*
- I shut it off, hooked the wire back to the module, started it, and the timing jumped back to 31*
- Still running, I started looking for the vacum lines, moved a couple and timing went to about 12* but as soon as I stopped the motor and started it back the timing went back to 31*
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Joined: Mar 2004
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From: Union, Washington
Originally Posted by badasshybrid
- The first time I checked it : running at idle, module untouched it was 31*
- Then I shut it off, took off the harness from the module, and unpluged the wire to the computer.
- I plugged the harness back up to the module minus one wire.
- Checked timing again : running at idle, timing was about 10*
- I shut it off, hooked the wire back to the module, started it, and the timing jumped back to 31*
- Still running, I started looking for the vacum lines, moved a couple and timing went to about 12* but as soon as I stopped the motor and started it back the timing went back to 31*
- Then I shut it off, took off the harness from the module, and unpluged the wire to the computer.
- I plugged the harness back up to the module minus one wire.
- Checked timing again : running at idle, timing was about 10*
- I shut it off, hooked the wire back to the module, started it, and the timing jumped back to 31*
- Still running, I started looking for the vacum lines, moved a couple and timing went to about 12* but as soon as I stopped the motor and started it back the timing went back to 31*
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It was overheating a little. It would serge, get hot for about 10 to 20 secounds the drop back to reg temp. ( while driving it wouldnt overheat sitting ) Sometimes it would get close to 250 for less than 5 seconds then drop back to normal. So I had it put on a computer at the dealer twice, They said it was a vacum problem the first time. And the gas caps the second time.
Post Fiend
Joined: Mar 2004
Posts: 6,056
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From: Union, Washington
How can it be a vacuum problem? If you hook up the computer the timing over advances (that's your overheat problem too), when you disconnect the computer the timing (that's called base timing and is what the dist is set to) is correct. The rest is controlled by the computer, so either the computer or one or more of the sensors has to be bad as it isn't likely that one sensor is causing the timing to over advance.
