CEL is being weird...help?

[Seanzyyy]

i have a 1990 240sx coupe (if it matters)

uhmmm...well recently i changed my spark plugs and plug wires due to the fact that one of the wires was f*** sooo i was basically running on 3 cylinders for the past few weeks

well, she runs fine and everything,no more misfiring, studdering, starting issues, etc.

but, for some reason,when i get to a certain speed, my CEL comes on.the second i drop from that speed, it goes away...

idk what speed exactly since my HUD wacks out in 5th gear for some reason.

but its when i get to around 2100 rpm in 5th it comes on.if i let off and my rpm's get below that, it goes away.

anyone have any idea at all?never experienced anything like this before..kinda weird lol

[prdquik]

maybe a loose wire . My car was doing that with the temperature gauge the other day. Whenever it was above 3,000 rpm the temp. gauge would drop and bounce all over the place. jiggled the sensor a little and it fixed it.

[Seanzyyy]

ok, i'll give that a whirl.do you think the same thing could be the reason for my malfunctioning HUD?