intermittent miss
05-29-2007, 05:07 PM
#1
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intermittent miss
Got a miss going on. It's intermittent. When the miss occurs, my wb reads full lean. I'd normally think secondary ignition, however when this miss occurs, the tach will drop ~500 rpm for an instant concurrently with the miss. It typically occurs while cruising between indicated 3k-3.4k rpm (but that may be because that's where I cruise at around town). But once I noticed it happening while decelerating in gear with my foot off the gas.
What would cause an ignition miss AND a simultaneous drop in RPM reading on the tach? CAS related? I do have a butt connection where the MSD box used to intercept the signal.
I have extra plugs & wires. Could throw them in to see what happens, but I'm not betting on secondary ignition because of the tach phenomenon.
What would cause an ignition miss AND a simultaneous drop in RPM reading on the tach? CAS related? I do have a butt connection where the MSD box used to intercept the signal.
I have extra plugs & wires. Could throw them in to see what happens, but I'm not betting on secondary ignition because of the tach phenomenon.
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05-29-2007, 05:47 PM
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Got a miss going on. It's intermittent. When the miss occurs, my wb reads full lean. I'd normally think secondary ignition, however when this miss occurs, the tach will drop ~500 rpm for an instant concurrently with the miss. It typically occurs while cruising between indicated 3k-3.4k rpm (but that may be because that's where I cruise at around town). But once I noticed it happening while decelerating in gear with my foot off the gas.
What would cause an ignition miss AND a simultaneous drop in RPM reading on the tach? CAS related? I do have a butt connection where the MSD box used to intercept the signal.
I have extra plugs & wires. Could throw them in to see what happens, but I'm not betting on secondary ignition because of the tach phenomenon.
What would cause an ignition miss AND a simultaneous drop in RPM reading on the tach? CAS related? I do have a butt connection where the MSD box used to intercept the signal.
I have extra plugs & wires. Could throw them in to see what happens, but I'm not betting on secondary ignition because of the tach phenomenon.
Is it rare, or somewhat consistent?
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Jerry a.k.a. 'FoundSoul'
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'91 Miata BEGi S3 GT2560 w/ MSPNP - 14.1psi - 253whp, 232wtq
'95 Miata n/a
A few other cars....
Jerry a.k.a. 'FoundSoul'
DIYAutoTune.com
'91 Miata BEGi S3 GT2560 w/ MSPNP - 14.1psi - 253whp, 232wtq
'95 Miata n/a
A few other cars....
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05-29-2007, 06:05 PM
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It started as occasional, but seems to be getting more frequent. I see these little spikes of 0 injector activity in my datalog. I assume it's related.
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05-29-2007, 06:35 PM
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It's the factory harness so that normally shouldn't be a problem... though I think the grounds were vampire tapped for the wideband which can damage them.
Ben-- email me your full datalogs so I can take a closer look.
Ben-- email me your full datalogs so I can take a closer look.
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Jerry a.k.a. 'FoundSoul'
DIYAutoTune.com
'91 Miata BEGi S3 GT2560 w/ MSPNP - 14.1psi - 253whp, 232wtq
'95 Miata n/a
A few other cars....
Jerry a.k.a. 'FoundSoul'
DIYAutoTune.com
'91 Miata BEGi S3 GT2560 w/ MSPNP - 14.1psi - 253whp, 232wtq
'95 Miata n/a
A few other cars....
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just a theory
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