Voltage to injector coil - Nissan Maxima '98


#1

1998 Nissan Maxima. Rough running, code says failure on cylinder 2. I start the car, pull the plug to #2 coil and do not notice any change in idle. Pulling other plugs does result in a change. I swap #2 coil pack with #4 with the same result: removing #2 plug doesn’t alter the idle, removing #4 does.

This leads me to believe it’s not the coil but perhaps the harness isn’t providing power to the #2 coil.

Anyone know how much voltage I should be getting at the connector to the coil?

Other ideas?


#2

The injectors get their voltage thru the ignition switch. So without the engine running and the ignition switch in the run position you should see battery voltage.

Tester


#3

I’m starting to think that’s not the problem after all. I put a plug into the coil and cranked the engine. I can get spark against the engine block so it seems that’s not the problem.

I have gas present
I have spark present

What remains? Compression on the cylinder?


#4

Yeah, compression…You have two threads running on this subject…Isolating the cause of your problem is a step by step process…


#5

+1 to Caddyman’s post. Refer to your other thread, where we’ve already provided detailed explanations.


#6

I have gas
I have spark

What remains?



Too much gas. I think you have a faulty injector.

One can check the injector signal from the ECU with a noid light. The ECU applies +12V to all injectors, then selectively closes the circuit to each individual injector by grounding that circuit through a transistor in the ECU. That is, when the voltage across the injector is high (12 V) the injector is closed; when the voltage is zero the injector is opening or opened.

The noid light test is essentially a rough test of the ECU.

Below: Engine disabled, noid at cranking rpm.

Below: Engine on, noid at idle rpm.

See if you can hear injector clicking by holding one end of 1/2 inch rubber tube to ear and other end of tube to injector at cranking rpm. Compare with good injectors. Sometimes works.

Pull injector and test its electrical resistance. Compare with injector from another cylinder if you don’t have specs.

Swap suspect injector with another cylinder and see if problem moves to swapped cylinder.