Hi, Let me give you some background first.
I just bought my first Mazda in my life a week ago. It's a Mazda 3s with 56k miles on it.
I went to Kragen, the guy suggested BOSCH Platinum +4 (Model # 4488), so I bought 4 of them.

I have changed spark plugs on Hondas, Acuras, Toyota, Nissan before, and I believe
all my procedures were correct when I installed the Bosch plugs on the Mazda3.
When I turned the ignition key after installation, the engine wouldn't start (I could hear the engine tried to start but failed),
the lights on the dash were blinking.

I put back the spark plugs that was originally on the car (they are FoMoCo ILTR5A).
I thought the car would start after I put the old plugs back on. BUT NO, it wouldn't start, the engine wouldn't start,
dash lights blinked. WTF was going on?
I tried to start the engine twice, I am not trying after that, cuz I am afraid it would damage the engine.

Can anyone tell me what's going on? How can I fix it? I did put every thing back on including the wires, tighten everything.

thanks in advance!

 

Did you do the plugs cause it was running rough, or just preventative maintenance?

Concerning the dash lights... did you disconnect the battery when you did the plugs? A loose connection there could cause problems.

And there could be sn issue with your key & the security system that might flash the dash. Generally it sounds like an ignition switch issue, but the car's young for that... unless it was flood damaged.

 

Just a piece of advice, In my experience, Ford products do NOT like Bosch plugs. Especially the +4's which are a waste of money. The +4's are a gimmick plug. They offer no gains, and increase thermal retention due to the increased metallic mass in the motor.

Splitfires, +4's +3's +2's and Diamondfire, E3's whatever. Those are all gimmicks that get you to waste your money for a "gain" that is RARELY seen. Stick with Motorcraft, NGK's, and I've used Autolites in my FoMoCo Taurus without any ill effects. I know the 2.3 is a different motor, but in all my Fords Bosch's refused to perform reputably. This is not to say Bosch makes a bad product (I run their Icon wiper blades on all my vehicles.), but rather that their ignition products do not run well in my vehicles unless they were OEM from factory.
[/rant]

Do you have an aftermarket alarm on the vehicle?