My max recently developed a drop in idle speed that feels like a slight bump while idling at stop. It also started stumbling on WOT that feels like a miss. At regular driving it seems fine, starts fine, etc.. No CEL light on.

I'm going to check the codes later today after work, but I'ms sure someone has experienced the same thing.

Knock sensor? Bad coil?

 

sounds like the exact same problems i've been experiencing off and on since i've had the car. the misfiring at WOT happened first and the idle bump (great way to put it!) just started within the past few months. with the misfire, i was never able to get a code for a specific cylinder but i can make the SES light flash at will.

first step was replacing the coils since it's a 99. got a set of non-99 used coils that fixed the WOT misfire for a bit, but then it has since come back.

plugs were changed, but i have one plug that has been rounded off and i have no way to remove it. it's no fun when you put the socket down there and it just spins instead of taking out the plug

i did have the KS ghost code but that was replaced and restored some kick... provided i didn't go WOT.

as far as the idle problem goes, i'm really leaning towards it being a problem somewhere in the electrical system. only reason i say that is because the frequency and severity of the bump will change depending on how much crap i have turned on in the car. my next step is going to be to sand/file/clean my ground points since i have noticed some corrosion.

hopefully we're not the only two that have this problem. it's nice not being the only one in the boat, but it's a boat i'd rather not be in at all.