Ok, I'm going to do my best to describe my problem I have. It's a 96 WS6. When it's not missing it runs great, pulls hard. When I first got it I noticed after I did a nice pull on the highway it would have a slight valve train noise to it but without any kind of misfire.

Now under normal driving it runs fine most of the time (can't hear chirping). If I give it more than half throttle, at about 2000-2500rpm it goes into this misfire mode almost like it's got a dead cylinder (chirping can be quite or down right obnoxious). I have to let off the gas completely for about 10-15 seconds for it to clear up (almost like the lifter has to pump back up?). This happens more often when the engine is warmed up completely.

Our Modis shows that when this misfire cycle starts it's cylinder #3 that's dead. But it also shows history misfires on nearly every cylinder.

Pulled valve cover off of bank 1. All the rockers are good (not loose). I can't visibly see any broken valve springs (was what I was thinking the noise was).

So based on all of that, I'm thinking its a bad lifter. The noise is best described as a "chirp", not a tap or knock. I wanted to see what you guys thought before I buy a set of lifters for it. I want to sell the car, and I would feel much better if it ran the way it should.

What do you think?

 

Any mods?

A "chirp" is definitely a unique noise. Video/audio would help tremendously.

 

Only mods are Hooker long tubes, SLP y-pipe, Loudmouth exhaust, electric water pump, and Holley TB.

Oh, and it has around 143,xxx miles on it if I remember correctly.

I should try to get a video of it...