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Originally Posted by TCHoward
Thanks Tom C. Never done diagnostics like this but hey there is a first time for everything!
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Tom:
It looks and sounds harder than it really is.
A fuel injector is a simple beast actually, not hard to understand at all.
It has a needle valve (also called a pintle) that is spring loaded into the injector body. There is a solenoid coil that acts as an electro-magnet which pulls up on the pintle when there's 12v's put through it. When the electromagnet pulls up on the pintle, the gas comes out and when the pintle goes down the gas stops.
See? Simple.
You're simply measuring Ohms of the solenoid coil in the fuel injector.
The typical failure is that the coil gets shorted because ethanol in the gasoline eats through an internal seal and starts chewing up the insulation on the solenoid coil. When that happens, the coil can no longer hold the pintle up long enough and the fuel injector does not squirt enough gas or no gas at all. As the conditions in the fuel injector changes, i.e., temperature, pressure, phase of the moon, rings around Uranus, the coil sometimes works, and sometimes not.
Viola!! Intermittent missfire.
The coils should measure about 12-15ohms depending on temperature and other things like different resistance in the circuit because of different wire length.
But that's really not a biggie, you're looking for a BIG difference.
If when you measure the ohms of the fuel injector coils and most are 12ohms give or take an ohm and one is like 7 ohms, you've found your bandit!
When three of my fuel injectors failed last year, one went short almost completely and two others were out of spec.
All you need is a volt meter with fairly long leads and the diagram that I sent. You will have to disconnect the correct connector on the ECM (lives just behind the drivers side front tire on top of the battery, you can't miss it), and then following the diagram measure the resistance between the pin on the connector and the 12v supply fuse which lives in a fuse panel on the side of the dash when you open the passenger door. The hardest part is figuring out which pin is which on the connector in the ECM. The diagram has the pin number on it, you just follow the diagram for each fuel injector down to where the connector is and you'll see the pin number on the diagram. Measure between that and the fuse and you'll have the ohms of the coil on the fuel injector.
Ready? GO!!
Let us know what you find.
I predict a plenum pull.
Don't worry, we'll help you there too!
No need to send out it out for repair, this is something that you can do at home with only a few special tools.
It will help if you're mechanical and aren't too intimidated by the fire breathing monster which lives under the hood of your ZR1
Give a starving man a fish and you've fed him for a day.
Teach him how to fish and you've opened a can of worms.
Welcome to the Brotherhood of the Beast!
