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

Aftermarket ecu? Need more fuel for ultra cold start?

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.

Are we supposed to assume the car is stock?

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.

Do you hear the pump prime adequately when the key is switched on?

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.

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.

How old is your battery? :dunno:

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?

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?

^Video Removed by user.

Yes, it was the IAT sensor. The problem has been resolved. This thread may be deleted or locked if the moderators would like.

We don't close or lock threads here. That shit is for pussy-ass forums. We aren't afraid of the future.