Stalling when clutched in

[speed]

Is it worse with headlights on? Just thought it could be the regulator in your alternator. Anyone else got some better ideas?


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[ED_MX5]

Check charging voltage. Have you got a multimeter?
Should be between 13 - 14 bolts roughly.

[manga_blue]

Google "idle dip" here and on miata.net.

[ED_MX5]

Check belt tension also, a loose belt can cause charging issues.
To check charge rate:
- engine off, connect multimeter leads to battery, black to black red to red etc.
Note voltage, should be approx. 12.4 to 12.6 approx.
Turn car on, connect leads again and note voltage, should be approx 13.5 to 14.5V.
If it is much lower, you probably have a bad alternator. Alternator also at fault if it reads higher, which means it's actually boiling the fluid out of the battery slowly.
Also be sure to check all connections on battery and alternator, make sure they are all tight and no excessive movement in the leads themselves.

Another quick test, is after you have checked voltage with engine running, turn on every electrical accessory you can think of, lights, radio, a/c wipers ect and re check voltage. If it is below the 13.5, you have a problem. the alternator cannot keep up properly
Hope this helps mate.

[manga_blue]

The battery/charging light comes on when the engine is turning so slowly that the alternator can't work. It's nothing to do with an electrical fault. Idle dip, or idle drop, is the single most common and most annoying fault of NA6s and NA8s. I reckon you've got it.

Try here for the cure: viewtopic.php?f=76&t=60434

In the short term, while you're trying to track it, you can avoid it a bit. When you're slowing to a stop leave it in gear until the revs fall below about 900rpm before de-clutching. The dip seems to result from a delay between where the ecu decides the engine needs no fuel and no air (i.e. as you're decelerating) and when it realises that you really just want it to idle and it hands over control of idle to the preset throttle bleed setting. It's not so bad when it's just transitioning from under 900 under ecu control to default idle control.

[speed]

Hmmm something is not right. Was the 14v with headlights on?
Cranking issue could be fuel pump but that doesn't explain your dip/stalling issue... I'm out.


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[hks_kansei]

THe rubber on the battery won't cause a problem unless the battery is touching metal and shorting.


As for the roughness, have you checked the plugs?
There is the potential that they are fouled and can't spark properly. I would suggest taking each one out and having a look, the tips on an MX5 will usually be brown/black and dry. If they're dark black, white, or wet, there's an issue somewhere.

WHile they're out I would suggest replacing them, it's only $20 for a set of new ones. Don't get fancy Iridium ones or any of that crap, just use plain old copper ones (I've always used NGK or Bosch and never had an issue) and replace them once a year.



Pretty much check the basics.

Is it getting air? (check air filter, check hoses for holes/cracks leaking air in)
Is it getting fuel? (the fact it can rev suggest it should be)
Is it getting spark? (remove plugs, rest a plug against the rocker cover and turn the car over, you should see a spark, repeat for all plugs... don't hold the metal bits, you'll get a decent shock)
Is it getting compression? (you'll need a special tool for this, a compression tester... if it's low on compression you can't do much outside of an engine rebuild)

[93_Clubman]

99% sure it's the fuel pump failing, not exactly dead but failing.

Russ, given your thoughts on a possible cause, if you remove the fuel pump/gauge sensor assembly from the tank then check the inside of the electrical connector block at the very top of the assembly - see here:
viewtopic.php?f=55&t=46425
You can test the connector block for continuity with a multimeter from the outside at the top of the fuel pump/gauge sensor assembly, so initially no need to open the tank up. Given the issue is intermittent, if this is the problem you should see reduced continuity, although it may test ok given it's happening under load.

But I'd also be checking the ignition timing; the 'Fuel Inj' relay in the engine bay fusebox; the fuel pump relay under the driver side dash; & the ECU for dampness or any damage to the PCB:
viewtopic.php?f=29&t=62258&hilit=no+power+below+3000%2A
viewtopic.php?f=29&t=60066&p=759454&hilit=timing+light#p759454