How do I test the coil rail on a 2001 to see if it's good/ bad

My Jeep has been idling rough and occasionally throws P0300, P0301, P0303, P0306 codes. I have been running through my list of possible causes and needed to know if there is a way to test the coil rail. Thanks.

akxj01 said:

My Jeep has been idling rough and occasionally throws P0300, P0301, P0303, P0306 codes. I have been running through my list of possible causes and needed to know if there is a way to test the coil rail. Thanks.

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ALSO,
1. I Tested injectors with multimeter: Good

2. IAC was replaced about 7,000 miles ago and TB was recently cleaned and is still clean

3. Plugs (Champion) have about 3,000 miles on them

4. I have the FSM...I saw nothing about testing coil rail

5. I recently pulled all the plugs, pulled fuel pump relay, ran engine till it died and tried to start a couple more times after than to get all the fuel out as possible, blocked throttle wide open, and did a compression test (cylinders are all good).......put everything back to working order and then started getting misfires and the codes I mentioned above

6. I am getting random misfire codes and misfire codes on cylinder 1, 3, and 6, so I guess it's hard for me to believe that all three injectors went bad at pretty much the same time period, right?

Does not sound like an injector problem. A vacuum leak somewhere is something to keep in mind for random/multiple cylinder misfires. Intake manifold, throttle body, also check all CCV plumbing/hoses to name a few suspects. If you don't stumble onto the cause of this, some basic vacuum testing may be in order; can be really valuable in isolating snaky problems.

No doubt you DID gap the plugs to .035". The FSM does list the resistance of the coil rail that you could test. Dielectric grease on the spark plug boots couldn't hurt in case of moisture issues.

winterbeater said:

No doubt you DID gap the plugs to .035". The FSM does list the resistance of the coil rail that you could test. Dielectric grease on the spark plug boots couldn't hurt in case of moisture issues.

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Champion plugs come with the .035 gap, and I double checked them. I'll have to look at the FSM again and see the coil rail resistance value. Already have the dielectric grease in there. Thanks.

birchlakeXJ said:

Does not sound like an injector problem. A vacuum leak somewhere is something to keep in mind for random/multiple cylinder misfires. Intake manifold, throttle body, also check all CCV plumbing/hoses to name a few suspects. If you don't stumble onto the cause of this, some basic vacuum testing may be in order; can be really valuable in isolating snaky problems.

Click to expand...

I'll check these points out. Thanks.