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08-02-2007, 02:51 PM
| #1 |
| Full Member Join Date: Jul 2007
Posts: 11
 | Idle & performance problem... OK, I posted about 6 weeks back on an issue with a '91 gmc 350, the motor would not idle and ran like it was on 4 cylinders. This morning we checked the fuel pressure, measured 12.5 psi under all loads, previulsy we swapped the cap & rotor as it looked like the rotor was rubbing the wrong way on the cap. So today we're looking at it again and the problem persists... I go to set the base timing @ 0*TDC, unplug the timing wire so I can set the timing and bam, runs smooth as a baby's a$$. plug it back in and it stalls. any ideas? could the comp have taken a dump? this motor was running perfect, then it sat for about a month with a dead battery, then when we went to revive it, it would not idle. we jumped it with my truck and left it connected for a while and it looks like the original battery in the chevy is working ok... several starts w/o a jump and strong juice coming from it. any input would be greatly appreciated... |
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08-02-2007, 02:56 PM
| #2 |
| Full Member Join Date: Jul 2007
Posts: 11
| I just took a look in the book on it and now it makes sense... we found a broken pot metal tab under the distributor, now i'm assuming it's the igniton module mounting tab which is now flopping around. I'll bet it has a hall effect pickup that is now gapped too far for it to pickup a good signal and that is what is causing the idle & performance problem... I'll go have a look and let you know what I find... |
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08-02-2007, 03:23 PM
| #3 |
| Senior Moderator  Join Date: Apr 2005 Location: Texas
Posts: 3,722
 | yeah sounds like a good bet.
__________________ John Wayne 2000 F-350 7.3L Powerstroke 4x4 |
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08-02-2007, 03:49 PM
| #4 |
| Full Member Join Date: Jul 2007
Posts: 11
| no luck on the tab... I do see that the wires for the distributor pickup, 1 green & 1 white are both cut, not sure if they are shorting out or not... do you know how to release the pin from the connector housing on them? I can slide a piece of insulation over it if I can get the pin out. |
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08-02-2007, 05:32 PM
| #5 |
| Senior Moderator Join Date: Apr 2005 Location: Texas
Posts: 3,722
| Without looking at it I can't be any help there. Been a long time since I've messed with a gasser. sorry 
__________________ John Wayne 2000 F-350 7.3L Powerstroke 4x4 |
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08-02-2007, 07:49 PM
| #6 |
| Senior Member  Join Date: Jan 2006 Location: South Florida (Palm Beach), originally from south of BOSTON
Posts: 644
| check the intake air control solenoid... it should be a soleniod that bypasses the throttle plate
__________________ im a straight shooter with upper management written all over me |
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08-02-2007, 08:12 PM
| #7 |
| Full Member Join Date: Jul 2007
Posts: 11
| well, we decided to swap the ignition module on the distributor hoping that was the problem and no go... still stalls when the timing wire is connected. I'm beginning to think the computer has a problem. Is anyone willing to disconnect theirs and measure the resistance from the computer side to ground? that is my next step... |
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08-02-2007, 08:14 PM
| #8 |
| Senior Member Join Date: Jan 2006 Location: South Florida (Palm Beach), originally from south of BOSTON
Posts: 644
| dont do resistance, it could lead you in the wrong direction.... do a voltage drop... your reading should not be more than 0.2 volts
__________________ im a straight shooter with upper management written all over me |
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08-02-2007, 09:32 PM
| #9 |
| Full Member Join Date: Jul 2007
Posts: 11
| OK, I'll do that. any idea what the range should be for the rpm scale? |
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08-03-2007, 01:53 PM
| #10 |
| Full Member Join Date: Jul 2007
Posts: 11
| OK, now I'm getting pissed... scottie your suggestion... measured .17ish or so. swapped the o2 sensor just now, tested the MAP, TPS, CT and looked real hard at the o2 before swapping it ($20 bux). Still not running right. No vacuum leaks, good fuel pressure on the output side of the fuel filter. what gives? what am I missing? |
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