Bouncing Rev Counter!!!
05-05-2004, 05:53 PM
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Bouncing Rev Counter!!!
Can anyone give any advise as to why my rev counter bounces between 1-7000 rpm on my 1990 sapphire cosworth. It is Pissing me Off!!!!
05-05-2004, 08:09 PM
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common problem on all sapphs,no one has pinned it down exactly but has been eliminated or reduced by cleaning the earths attached to the inlet manifold or breaking the block connectors along the back of the engine bay and giving them a good clean out,it appears to be a stray pulse being picked up by the rev counter and giving false rev count
had the same problem on my 92 sapph and eventually it went away after doing the above
had the same problem on my 92 sapph and eventually it went away after doing the above
06-05-2004, 11:18 PM
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Velocity is on the right track..
It is caused by interference on the ignition amplifier inputs, generally due to poor earth connections from the ignition amplifier/coil circuits.
1, Check condition and security of all connections to the coil, ignition amplifier, crank and phase sensors (on the side of the distributor)
2, Find the earth terminals on the inlet plenum chamber that bolt down the brown ground wire terminations from the loom - dismantle if neccessary to clean and refit.
3, Similarly ensure the cleanliness and security of the ground connection on top of the bulkhead just in front of the battery.
4, If it's a 4x4 - check cleanliness and security of the three loom connectors on the bulkhead above the back of the camcover.
you will be unlucky if this doesn't sort the problem. The jumpy tacho thing is the first indication of this problem.. if left to deteriorate, it will often result in misfire as well.
It is caused by interference on the ignition amplifier inputs, generally due to poor earth connections from the ignition amplifier/coil circuits.
1, Check condition and security of all connections to the coil, ignition amplifier, crank and phase sensors (on the side of the distributor)
2, Find the earth terminals on the inlet plenum chamber that bolt down the brown ground wire terminations from the loom - dismantle if neccessary to clean and refit.
3, Similarly ensure the cleanliness and security of the ground connection on top of the bulkhead just in front of the battery.
4, If it's a 4x4 - check cleanliness and security of the three loom connectors on the bulkhead above the back of the camcover.
you will be unlucky if this doesn't sort the problem. The jumpy tacho thing is the first indication of this problem.. if left to deteriorate, it will often result in misfire as well.
11-05-2004, 10:00 PM
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are you sure its not when you loose traction and its the rev counter bouncing to 7000rpm. does it do it more in the wet. have you checked your tyres, driven throught any oil lalely. plus does when it hits seven does it bang and put a flame out of the exhaust.
im sure i will have an answer if i knew the full spec, just a few ideas mate!!!!
im sure i will have an answer if i knew the full spec, just a few ideas mate!!!!
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