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Miata starts for 2 seconds then dies

Hello all,

I have a peculiar problem, but first a little background.

The other day I went to start my miata, after it had been sitting for awhile (~1 month). It was difficult, but it did start, but began to sputter and shake badly. Even backfiring a couple of times, but it continued to run (albeit badly).

I investigated under the hood, and discovered that a couple of plug wires were touching. I assumed that this was the problem, and moved the wires so they wouldn't touch.

When I got back in, I started the car and now it won't keep running.

For the brief period that it does run, it runs flawlessly. The rpms go up, just as they should and it runs smoothly, but almost as soon as it starts it dies. I suspect something electronic, like the computer is killing the engine.

I remember in a Chevy my company had there was something known as a "crank position sensor" that would tell the computer when to fire a plug, and if the computer failed to get a signal from the sensor, the computer would shut down the engine for safety. I think there must be something like this going on in my car.

Here are the symptoms:

  1. Turn key, engine starts, rpms rise, then car dies within a couple of seconds.

  1. If I turn the key again, the engine will crank, but not start.

  2. If I turn the key to the off position before I crank it again, the engine will start/die again.

  1. If I turn the key on-off-on-off-on-off-on in rapid succession, I can keep the car running, with rpms constantly going up and down, as would be expected.

That last symptom is why I think the problem isn't fuel, but electronic. Without fuel, I couldn't keep it running at all. And if it wasn't capable of sparking, it would never start in the first place. I have heard about ignition switches being a common problem, but again, I wouldn't think it would start in the first place.

Any ideas?

Thanks, Marc

Reply to
Marc
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We need to know the year of your Miata.

Reply to
Lanny Chambers

If you have a newer car, you may want to try the other key. You may have a bad transponder in your key, which will kill the engine.

Reply to
Dana Rohleder

Sorry, it is a 1992.

Reply to
Marc

I'm thinking out loud-- Sitting for about a month How much fuel is in the tank? and how long was it there? Do you have any sort of a "varnish smell" rather than the usual fuel smell? Was the Miata in a damp or dry storage location? When it quits, does the exhaust smell of raw fuel? If you attach a timing light to the #1 lead, is it still flashing when the engine quits?

A plugged up fuel filter might cause your problem, and coupled with a leaking injector, might cause fuel to be present in the intake manifold, allowing the engine to run rough for a few moments.

The igniton switch has a start and run position. It may be that you have ignition in the start position, and not in the run position. I would think that it would not run at all if the cam sensor was shot. If one of the coil packs or igniter is bad, I suppose that you might get a run rough and die symptom.

Since I have an NB, my wiring diagrams are incorrect for a 92. I would suggest that you obtain the diagram and use a voltmeter or 12 volt trouble light to see if the run position on the ignition switch is working properly. I'd also see if the fuel pump gets power just while the starter is engaged, or also in the run position. I believe it will have power for a short period in the run position, then, if the engine is not running, power is removed from the fuel pump.

It's sort of an elimination process to find the problem. You start with possible causes that can easily be checked, even if they are not the most probable causes. Then you progress to those that are harder to check.

Reply to
Chuck

You have the symptoms of a mass airflow meter that's not plugged into the harness. Check the connector and wiring. I don't think this is related to sitting for a month--that's not long enough to cause the usual storage problems. Unless the battery has run down so far that the ECU won't run; do the lights and horn work OK?

Reply to
Lanny Chambers

Not that I have noticed

It was parked outside, although the interior of the car can get some moisture after a heavy rain

I have smelled fuel, but assumed this was due due lack of spark.

I'll try tonight.

The engine only ran rough until I noticed the toughing plug wires, and it kept running. Now it runs smooth every time (but only after turning the key off), but dies.

Can't comment. All I know is that the key returns to "run" position after I have turned it (forward, against the spring) to crank the starter. The engine dies (after running smoothly) immediately after, even if I keep the starter turning.

I am in the middle of moving (between houses) and all my manuals are in boxes that are in transit. I was about to move the car to the new house when this happened.

I've tried unplugging/re-plugging most of the connectors I could see easily in the engine bay. I suspect that I created a problem when the engine was running rough, until I separated the plug wires from one another. I'll keep looking for loose wires until I can find my manuals.

Thanks for your help.

Reply to
Marc

I don't have access to my manuals right now (I am in the middle of moving). It's possible I shook something loose during the initial rough idle, before I separated the plug wires.

I saw the computer codes on Miata.net. I'll try those as soon as I am able, and see if I get an "8".

Thanks.

Reply to
Marc

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