I have a 98 z28. I was driving it the other day and was pulling away from a stop sign. While I was accelerating I noticed a loss of power. I had the radio pretty loud, so I turned it down and I could hear a "fluttering" sound coming from the engine . The oil pressure was fine, the temperature was fine.

So I ended up going back home and popped the hood. The noise is coming from the passenger side of the engine. It's not very loud while idling, but noticeable. The flutter/knock gets louder and faster when the I rev the engine. The first thing I thought was it had spun a bearing. So I drained the oil and stuck a long magnet in the oil pan several times - it came out clean every time (no metal pieces). So I'm pretty certain it doesn't have a spun bearing (oil pressure is still normal).

I checked for exhaust leaks - nothing. The only other thing I can think of is a collapsed lifter. Does anybody have an idea of what else it could be before I take the heads off and search for the collapsed lifter?
Thanks.

 

have you taken the rocker covers off and had a look inside?? See if there is play in the pushrod, if there is and you take t out and its not bent or the spring hasn't failed is prob the lifter then

let us know what you find

 

With the hood open is it louder when you are under the car or under the hood? I’ll assume up top. There are a lot of things that can make the noise you described but few of them that would affect the power the car had. When a bearing spins to the point if effects power the motor normally becomes hard to start. It will almost sound like a low battery. Wrist pins, flex plate, stretched rods, piston slap will all cause noise like you describer but you will not feel a lose of power until the damage was very sever. Based on your post I would say the valve train is the likely problem. It could be a lifter or a broken valve spring. I am leaning toward valve spring based on your description. Either way you will need to pull the valve cover to see what is going on.

 

yep, find the noise first then go from there. could be something is setting off the knock sensor. any trouble codes?

 

Thanks for your replies. I have taken the valve cover off and checked each rocker, spring, and rod. They all seem fine.

Gorn, the noise is coming from the top. I've started the car about 5 times since it started doing this, and 2 of the times the car stalled out right away after starting - which is never did before. It didn't seem like it was struggling to start like it had a low battery though, it fired right up. Although after the car would stall, it would take a second or two for it to start again. It just seems like the idle is too low when it first starts up. Could that be a symptom of a bad lifter? Or something else?

Craby, the only codes I'm getting is "random/multiple misfire" which I've been getting since I've owned the car.

 

How loud is the noise? Does it sound more like a hollow clunk, or a click/clack? If more of a clicking sound, it could be a bad injector.

 

This isn't my video or car, but it sounds exactly like this:
http://www.youtube.com/watch?v=TJYX2...eature=related

Seems to be coming from the same spot in the video too.

 

The video you posted was a loose plug but it sounded a lot like a bad lifter. You could try changing the oil to see if the lifter comes around. Sometimes switching to a synthedic oil or just clean oil will clean out the stuck lifter.

 

Def doesn't sound like a rod knock. When you checked your pushrods to see if it was the lifters, did you check them all at once? Unless you checked them the same way you would adjust them (unloaded on the heel of the cam), there still could be a dead lifter. Even though you might not see a bad lifter with the engine sitting idle, that doesn't mean it's not collapsing as the engine is running. Internally, the lifter plunger is spring loaded, but it pumps up hydraulically as the engine is running.

 

i have used a screw driver to push on the lifter side of the rocker when the motor is running. if the lifter ticks when u push on it its set to lose or is a bad lifter. i would look into the random misfire if i were u.