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How to check and adjust the timing on Mk1 MX5

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Joined: Mon Jan 02, 2012 11:13 pm

How to check and adjust the timing on Mk1 MX5

Postby doctorMX5 » Wed Feb 05, 2014 6:23 pm

How to adjust the timing on Mk1 MX5

Tools: Sturdy paper clip, 12mm spanner, Strobe Timing light

Warm the engine until Revs drop to normal operating idle speed. Place paper clip between GND and TEN in the diagnostic port (situated on the left wing under the bonnet).
The port map is on the underside of the diagnostic port's lid – if its missing be careful and get-it-right before you connect anything! Image
Once GND and TEN are connected the engine's revs may change somewhat. Check your rpm. It should be 850. If it's not 850 adjust the air/bypass screw on the throttle body until tacho reads 850. Image
If you are not confident about the tachometer's accuracy (perhaps your instrument dial panels have been changed from standard) you will need to ascertain the rpm another way, for example a strobe timing light with rpm built-in.

Slacken the 12mm adjuster bolt head on your Cam Angle Sensor. Image
Connect your Strobe carefully avoiding any chance of wires or crocodile connectors getting near moving parts of the engine! Red goes to blue plug on left inner wing near the diagnostic port, Image
black goes to any good earth,Image
the coil clamp – which detects the spark - goes on No1 HT lead with the arrow pointing (in the electrical sense) towards the spark plug. Image
Now carefully avoiding any chance of wires or fingers getting near moving parts of the engine hold the trigger and shine the strobing light onto the crank pulley. Image
The picture shows: a tiny notch in the pulley wheel marked yellow, T for top-dead-cantre, 10 for normal setup, and the position of 14degrees BTDC which my car shows. Image
Now have a friend rotate the Cam Angle Sensor a little this-way-and-that until you have the desired timing (each increment on the timing cover is 2 degrees). Now go back and check your RPM and adjust back to 850 if necessary Now re-strobe and adjust CAS angle if necessary.. Lock the CAS 12mm adjuster bolt. Now remove the paper clip or jumper.

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