Idle speed?

Sort of an odd thing... the Miata idles at about 1250rpm while waiting for a light but if I put it in neutral the idle drops to a proper

750rpm or so. Doesn't matter if the clutch is in or out, it idles at 750 until I put it in gear, then it immediately goes to 1250.

Dragging clutch? Maybe? I'd think a dragging clutch would slow it not speed it up but maybe the FI is compensating for the drag or something?

Reply to
XS11E
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What year Miata? Since you have a high idle vs low idle. Usually the normal idle is ~1000 by tach (850-950) Check for anything that might affect the idle speed. There is a switch on the tranny that might cause odd idle readings A/C and P/S options also have idle kickup ability. Engine temperature sensors are seperate for the gauge and the ECU input, so the rear temp sensor output on the engine is suspect. FI often has a engine control scheme that introduces another level of cause and effect. Since I don't have the foggiest about yours, I cannot comment on it.

Reply to
Chuck

"Chuck" wrote in news:q5Kah.13$ snipped-for-privacy@newsfe20.lga:

Top posting corrected:

1992.

I can't think of anything that would depend on the transmission being in neutral to reduce the speed????

I didn't know there was a switch on the tranny, there is/are switches on the clutch but it makes no difference if the clutch is in or out.

Again, I can't see how the transmission being in gear or being in neutral could have an effect on the above?

Reply to
XS11E

for what it's worth,

first, some Mazda's of that era (MX3 & MX6) did have a signal from the tranny (manual) to the ECU that was low-true in neutral. I used it to pick a relay enabling a remote starter on my son's '93 5-speed MX6, so it wouldn't activate if he left it in gear.

second, after my daughter's '92 MX3 died on the side of the road one day, our mechanic diagnosed a bad distributor. He found a replacement at the auto wrecker's yard, which solved the no-start problem, but left the check-engine light on. Further analysis revealed that some versions of that

1.6l engine used a sensor at the front of the crank, others relied on a sensor in the distributor(identified by a 4-wire connector). The replacement dist. had only 3 wires in the connector. The other symptom of the sensor being absent was a fast idle whenever the tranny was put into gear... any gear... ie: taken out of neutral. A few weeks later said mechanic found another distributor which did have the sensor and 4 wires... fast idle problem gone.
Reply to
Pete

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