multiple missfire codes

[Einmit]

2005 jeep liberty 3.7 gas 4x4
Had code #6 misfire runs a little ruff. Get home and swap #6 coil with #1, still #6 misfire. Changed spark plugs, still misfire #6 and now its #5 misfire also. So changed around coils and now have misfire codes for #1, #5 and #6. Pulled all coils and plugs and did compression check. All 120psi. Did individual coil and plug to check for spark and all the coils and plugs had visible spark on 2,3 and 4 wires connectors, but the same coils and plugs that had spark had no spark on 1, 5 and 6. Swapped out the asd relay with other relay and still no difference. Jeep will not quite start now with 3 dead cylinders, almost though. Wazzzup?

 

[JPNinPA]

Did you check the injectors? Have you verified fuel pressure? Was it 49.2 to 54.2? I think the 120 lbs is low overall. I'll look it up for that engine but I think 125 or 130 is a min. 150 and above is expected with less than 25% between any two cylinders.


Checked the numbers in two places and the specs are 175 - 225 lbs no more than 25% delta max.

Regards,
JPNinPA

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[Einmit]

So my way of thinking it's electrical, but your saying it may be fuel issue. But it's only firing on 3 cylinders, so your saying if the fuel pressure isn't right then it wouldn't fire on that cylinder. I will check the injectors. Thanx

 

[JPNinPA]

Ok I just reread what you wrote in the first post. You are not getting spark in 1,5&6. Check the wiring and connectors.


What plugs did you use when you replaced and what was the gap? Was there oil on the plug or coil boot that goes over the plug? The plug could get shorted due to the valve cover leaking or anything getting down there.


Regards,
JPNinPA

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[Einmit]

When I said I changed plugs I meant moved them to diff coils. There was no oil anywhere. Gap was 40 thou. I will give all the wiring a good going over. Thanx again

 

[Einmit]

Checked wiring, found nothing wrong. I am unable to check fuel pressure at this time. Dam, I was hoping that it was something simple. Thanx for all the info so far.

 

[JPNinPA]

Going back to your compression test. Expected is 175 to 225. I'm guessing you didn't have a good seal or didn't crank 3-5 times.

Make sure there are no contaminants on the coil boot or plug including arcing burns. All I see are issues with the valve cover gasket going bad and contaminating the plugs and boots causing misfires.
Post up a pic of the plugs and coil boot.


Regards,
JPNinPA

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