rumble in the jungle

[panhandler]

Good Folks - I have a 99 EB 5.4L 4x4, 133k miles and a problem. Between 35-50mph, with overdrive on, I get massive misfire/rumble/jerking/stuttering. It's particularly bad under load (driving uphill, etc). When I turn overdrive off it improves considerably but still acts up some. Is this more likely coil packs/plugs or do I have a transmission issue (or none or both)? Any help is greatly appreciated!

 

[toms89]

It can be several things but what your describing to me sounds like a misfire under load. Higher loads increase the demand on the ignition system.

Did anything precede or lead up to this occurring or did it happen overnight?

 

[panhandler]

It's my wife's car so I don't drive it regularly - it seems to be progressively worse. Also, the check engine is throwing a code P0455 for large EVAP leak but not sure this is related as the misfiring has gone on long before the code.

 

[toms89]

I think the first thing I would do is install new sparkplugs making sure they are properly gapped if they have not been changed recently. Hopefully if you are having misfire it will be obvious on one or more of the plugs. This will also let you know if any moisture has gotten into the plug wells.

While your there check carefully for vacuum leaks.

This should eliminate or confirm them as the source.

 

[panhandler]

Thanks!

 

[Ward]

If you're doing plugs, change the coil packs as well. I had a similar problem with mine, and new coil packs solved it.

 

[TactialMonkey]

speaking of new coil packs did you get OEM or performance ones? I am curious to see if the packs help at all I know I will put my life on E3 spark plugs over any one else but now its the coils i'm debating over

 

[FordandPolaris]

I use whatever the premium coil pack brand is at O'Reilly since they are lifetime guaranteed. Probably will just pull them out and put them in my next truck too haha.

 

[walnuts4x4]

sounds like a issue I had a while back.... I went with globalautomotive on ebay and got 8 new COPs and autolite double platnium plugs and hasn't had an issue since

 

[Ward]

speaking of new coil packs did you get OEM or performance ones? I am curious to see if the packs help at all I know I will put my life on E3 spark plugs over any one else but now its the coils i'm debating over

I bought a set off these off ebay:
Eight New Copper Wire Ignition Coils USA Made 4 6L 5 4L | eBay