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Old 06-17-2014, 12:03 PM   #1
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Default Strange Ignition coil dealings

Ok so I wanted to bring this up to see if anyone else had this problem in the past.

I own a 95 miata bone stock. My neighbor has a 95 miata has spec exhaust and that is it. He had a Mazda 323 valve cover on his car and before he sold it asked if I wanted to switch because he thought stock would sell better. I was all for it. So I go to his house switch valve covers and coils because he had a nice bracket to fit the 323 valve cover. Put the two cars back together and his runs mine starts for 3-5 seconds and dies over and over and over.

So after looking at it for over an hour trying to figure out what I messed up I decided to switch back. Boom both cars run fine. Then out of curiosity I switched just the coil packs. Same thing happens.

So both cars are 95's both ran perfect before the swap and only one ran after. After playing with them we determined his car will run with either coil pack and mine will only run with the one. This makes 0 sense to me can anyone shed some light on this?
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Old 06-17-2014, 01:12 PM   #2
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Both cars have stock ECU?
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Old 06-17-2014, 01:16 PM   #3
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your car is a 4 wire car, his is a 3.
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Old 06-17-2014, 01:53 PM   #4
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yes both cars have stock ecu

Leafy what do you mean one is 4 wire and one is 3 wire
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Old 06-17-2014, 01:56 PM   #5
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95 is the year with the mid year change to the number of wires on the ignition coils. The early 95s use the ignition coils to drive the tach, but that signal also goes back to the ecu for some silly reason and 4 wire cars wont run for long with 3 wire coils. I think for some stupid reason on the 4 wire cars that the ecu use the tach signal to know if the engine is running and disables the fuel pump if it doesnt get the signal.
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Old 06-17-2014, 02:45 PM   #6
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Well thank you very much leafy this explains a whole lot. I thought I was going crazy and managed to mess something up repeatedly. So I am not crazy it is just the way the cars are wired. Awesome thanks for the clarification.
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Old 06-17-2014, 02:47 PM   #7
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I bet if you check the build dates yours is on the older side for a 95 and his is on the new side.
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Old 06-17-2014, 02:54 PM   #8
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His is an 11/95 car I dont know what mine is I will check when I get home. funny with his car the emissions sticker under the hood says conforms to 1996 emission and the sticker on the door jam says 95. I will check the build month on mine I assume it is prob an early one.
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Old 06-17-2014, 04:13 PM   #9
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Quote:
Originally Posted by Leafy View Post
95 is the year with the mid year change to the number of wires on the ignition coils. The early 95s use the ignition coils to drive the tach, but that signal also goes back to the ecu for some silly reason and 4 wire cars wont run for long with 3 wire coils. I think for some stupid reason on the 4 wire cars that the ecu use the tach signal to know if the engine is running and disables the fuel pump if it doesnt get the signal.
I ran my 94 with a 3 wire coil pack for 25+ miles while sitting in DC traffic with no problems years ago. I had picked a 94 coil pack from Rosenthal Mazda in the morning. I got home and got it out of the box and realized it was only a 3 wire coil pack. Threw it in the car and then drove back out to Rosenthal to exchange it.
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Old 06-17-2014, 04:17 PM   #10
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Quote:
Originally Posted by shuiend View Post
I ran my 94 with a 3 wire coil pack for 25+ miles while sitting in DC traffic with no problems years ago. I had picked a 94 coil pack from Rosenthal Mazda in the morning. I got home and got it out of the box and realized it was only a 3 wire coil pack. Threw it in the car and then drove back out to Rosenthal to exchange it.
Stock ecu? fp not jumpered to ground? I got the "the car only runs for a little bit at a time" from mnet. And someone else guess that it shuts off the fuel pump if it doesnt get the signal, but sounds like perfectly good mazda ecu logic.
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Old 06-17-2014, 05:14 PM   #11
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Quote:
Originally Posted by Leafy View Post
Stock ecu? fp not jumpered to ground? I got the "the car only runs for a little bit at a time" from mnet. And someone else guess that it shuts off the fuel pump if it doesnt get the signal, but sounds like perfectly good mazda ecu logic.
Honestly I don't remember if stock ecu or an ms1. It happened back in 07.
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