Running rough.... sometimes
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Joined: Aug 2002
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Running rough.... sometimes
My 88 Efi Bronco will run and idle rough at times. Sometimes it runs great. When it runs rough, it bucks/surges through all ranges of rpm and in all gears. if it is running poorly, it idles very roughly.... But here's the thing. If I pull a vacum line from the vacum tree, the rough idle goes away and it runs great (but idles a little high). Am I running rich or lean? Should I be looking at the fuel pump/filter/injectors? If I let it sit for a week it runs great when I start it up, but the roughness returns shortly. Has anyone else had these symptoms? Any thoughts a hugely appreciated!
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Joined: Dec 2001
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From: Southeast FLA
Running rough.... sometimes
[updated:LAST EDITED ON 24-Nov-02 AT 04:24 PM (EST)]Err, I hate answer this, but since it has worked for so many people... try doing the EGR block-off plate (plenty of posts about them in this forum) and see what happens.
If you're pulling a vacuum line and allowing the manifold to pull in more regular air, then it runs better, it seems to me that (and I could be wrong here) it's desiring more air for the burn. If your EGR is dumping too much exhaust gas in the plenum, or is doing it at the wrong times, your idle is going to suck.
Still, the increased RPMs that come from a pulled vacuum line might be hiding your problem, so you might not have found the 'fix' for it yet.
Check your plug wires while it is running (perhaps there is occasional arcing from a worn insulation area), and change 'em if they're too old (same goes for your plugs, your TFI coil (crappy & unreliable coil anyway - buy a MSD TFI-replacement coil), you cap, rotor and plugs).
The IAC valve might be something to look at as well.
Best,
If you're pulling a vacuum line and allowing the manifold to pull in more regular air, then it runs better, it seems to me that (and I could be wrong here) it's desiring more air for the burn. If your EGR is dumping too much exhaust gas in the plenum, or is doing it at the wrong times, your idle is going to suck.
Still, the increased RPMs that come from a pulled vacuum line might be hiding your problem, so you might not have found the 'fix' for it yet.
Check your plug wires while it is running (perhaps there is occasional arcing from a worn insulation area), and change 'em if they're too old (same goes for your plugs, your TFI coil (crappy & unreliable coil anyway - buy a MSD TFI-replacement coil), you cap, rotor and plugs).
The IAC valve might be something to look at as well.
Best,
