MX5Ireland

Hello there,
Mine is a 1.6 Eunos year 1991. I decided to try to alter the timing to 14 BDTC as opposed to its existing setting of 10 degrees. I also introduced a free flow intake filter system to replace the existing standard one. Typical of many owners I would suspect. I followed internet instructions and connected the GND and TEN on the diagnostics cube . I noticed the revs jump a bit when I did this . I brought them back to 850 with the idle screw and made the adjustments to the timing. Then I removed the jump wire from the cube . However the rev needle will not now return to 850 revs without a 5 second delay. When I reinsert the jumper wire to the diagnostic cube everything works fine again . I now have left the wire in permanently in the diagnostics cube because the pause in returning to idle is driving me nuts . Any advice .... ?

Engine should not be running when doing diagnostic check. Just ignition on position

Thanks for reply. However, and correct me if I am wrong, but to set timing with a strobe light the engine must be turning and GND and 10 connected. When this is achieved is the jumper connection then not disengaged?

Set the timing while engine is running obviously but jumping the terminals then re sets new changes ???

Now Im totally confused. It seems to run fine with the terminals permanently jumped ....maybe I should leave it that way. Chinese cars!

did you happen to fiddle with the ISC while doing the idle?
Troubleshooting guide is here : http://www.miata.net/garage/isc.html

No Steve, I did not touch the ISC , just kept the process simple following a proceedure outlined on quite a few web sites.The jumped idle revs can be set at 850. When the jumper is removed they always drop to 500 or so . I cannot close that gap as there is always about 300 revs between jumped and non jumped. If I adjust the unjumped revs to 850 they become slow to return there when the engine returns to idle from high revs. If left jumped things seem fine. By jumped I mean connecting 10 and GND.