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Old 01-05-2016, 04:32 PM   #1
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Default Difficult/Impossible to start when cold

Hello everyone! My 2001 Miata has been recently giving me issues where it refuses to start when cold. I can just crank it and crank it and it just won't start most of the time. Sometimes it will actually start for some reason, and if it does actually idle, it won't die. It runs perfectly when it is running good, it's just hard to start. It also will start in like, the first crank when warm. Anyone know what this could be? I've recorded a video of me trying to start it below.

Thanks for the help!
Nick

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Old 01-05-2016, 05:16 PM   #2
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Aftermarket ecu? Need more fuel for ultra cold start?
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Old 01-05-2016, 05:19 PM   #3
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That's what I was thinking, maybe the fuel pump. But wouldn't it not run at all once started? That's what perplexes me. If the fuel pump was dying, I wouldn't think it would run as well as it does.
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Old 01-05-2016, 05:29 PM   #4
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Are we supposed to assume the car is stock?
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Old 01-05-2016, 05:30 PM   #5
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Do you have an aftermarket ECU?
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Old 01-05-2016, 05:36 PM   #6
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Quote:
Originally Posted by psyber_0ptix View Post
Do you have an aftermarket ECU?
Excuse me, I forgot to include modifications. It is using the factory ECU, with a cold air intake, header, rebuilt engine, and lightweight flywheel. New spark plugs, coil packs, ignition lines, belts, and fuel filter.
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Old 01-05-2016, 05:41 PM   #7
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Do you hear the pump prime adequately when the key is switched on?
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Old 01-05-2016, 05:44 PM   #8
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Turn the key to the on position for 5 seconds, but don't try to start it, then back off. Do that twice and try to start it.

If that don't work, 3 times and then try to start it. See if that makes any difference.

Also, do a compression test when cold.

I'd also pull the plugs, make sure they're NGK at .039" gap and in good condition, not oily or wet.
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Old 01-05-2016, 06:07 PM   #9
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Girz03: I hear the pump click when I put the key on ignition, but It is hard to hear the actual pump.

Patsmx5: I just tried that. Didn't work. I don't know if it is worth doing a compression test, as my engine was just completely rebuilt less than 10,000 miles ago. I'll pull the plugs soon to check the gap. I know they're NGKs.
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Old 01-05-2016, 06:16 PM   #10
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How old is your battery?
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Old 01-05-2016, 08:22 PM   #11
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It's cranking plenty fast enough. Battery isn't the problem.

Sounds like it almost catches, but maybe on only one or two cylinders. I'm guessing spark. Electrical connections all tight? Plug boots, coil connections, CAS plug.

Pull the plugs, as stated above. Wet, it's not fuel. Dry, it probably is. When was the last time the fuel filter was changed?
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Old 01-06-2016, 10:33 PM   #12
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I checked out the IAT sensor, and sure enough, when I recently unplugged it I plugged it back in and somehow a pin missed a connector. Now it starts reliably, even when cold, but it sure doesn't sound happy about it. I recorded a small clip after it started up on either the first or second crank today. It's so weird that although it starts and once warmed up it runs and idle perfectly, it sounds like crap when started cold. It sounds like it is missing a bit in the video, but keep in mind that when I put the camera next to the exhaust, I do have a hole in the muffler, so that may make it sound like it is missing here. Hard to tell.



So the car starts, but I would still like the address the rough start up idle. Any ideas? Could it still be a dying IAT sensor?
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Old 01-09-2016, 11:57 AM   #13
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^Video Removed by user.
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Old 01-11-2016, 11:05 PM   #14
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Yes, it was the IAT sensor. The problem has been resolved. This thread may be deleted or locked if the moderators would like.
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Old 01-11-2016, 11:16 PM   #15
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We don't close or lock threads here. That **** is for *****-*** forums. We aren't afraid of the future.
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