Hello looking for help on figuring out my problem on 1998 ram 1500 5.9 magnum.
So I randomly have a misfire or rough idle. The truck can be idling for hours and everything is good, shut it off and start right away again it will sit for a minute and will start misfiring and at times will stall. When it stalls fire it up right away and it will idle normal for hours. When it does misfire if you throttle it it goes away for a minute and then again misfire until you shut it off and re start it, and everything is back to normal.

Full Engine rebuild 1000 Miles ago. (It did that before rebuild as well) All new sensors - map, IAC, TPS, crank shaft position, new distributor, wires, coil. Then I read that it could be coolant temperature sensor, replaced that and still same problem. Timing was set. T stat replaced.
Any advice will be much appreciated!
Thanks
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Has a check engine light come on? If so, are there any pending or stored codes displayed via an OBD2 scanner?

 

Yes once in a long while, like once a week it will throw a check engine light on and code cyl 8 misfire, current. I clear it and it doesn't show up for a while.

 

What plugs do you have in it?

 

NGK Copper / Nickel V-Power

 

Did you set the gap installing the plugs?

 

No it was preset at 0.044"

 

It may have been preset when it was made, but, that does NOT imply that it is still set when you get them..... I ALWAYS recheck plug gap before installation. Ya never know what they have been thru to get from point of manufacture, to your hand.....

 

Agreed, All 16 I just put in my Hemi were atleast .010" to narrow, they even came packed in the plastic protector tubes. Also .044" seems plenty wide for a magnum, I thought they were closer to .034"?

 

As per the service manual, Champion RC12YC set at .035.