Valve Float at Higher RPM???

[Ryatt-Motion]

Hey guys, i have noticed that from time to time my car run kind of rough, depending on the weather. I know I have two 02sensors that need replacing, but, my bigger problem is, there is some serious valve float going on when I hit the throttle. I have tried different gas (brands) changed the plugs, wires, seafoam'd the engine, changed to 10-30 oil, and nothing, its really driving me nuts, it almost feels like the timing is retarding at high RPM, any ideas??

[MasterZ]

i dont see where the gas type is going to correct valve float..

how many miles are on the car? maybe time to change the spings out. Is the top end stock, cam?

[MasterZ]

i would start off changing the O2 since you already know they need replacing..

[Ryatt-Motion]

Jason, I was thinking the bad gas might cause the knock, or float.

The car has 93,500 miles and it bone stock. Nothing has been done to the engine at all. What do you recommend I do in terms of testing the springs and stuff?

[MasterZ]

Originally Posted by Ryatt-Motion

Jason, I was thinking the bad gas might cause the knock, or float.

The car has 93,500 miles and it bone stock. Nothing has been done to the engine at all. What do you recommend I do in terms of testing the springs and stuff?

well I say first you need to determine if it is actual valve float or knock. they are 2 different things.

Valve float I would think would be rare with an all stock motor with that mileage.. typically it happens with a larger cam and the springs are not strong enough then at higher RPMs the springs can't close the valve quick enough so they tend to stay open a bit ( valve float) Not saying it isnt possible, cause you could have a bad spring, cause over time they will weaken.

More than likely it is a sensor going bad and giving you a false reading... Is your check engine light on? I would start by changin the O2's then reset the computer and see what she does. Then go from there.

[Ryatt-Motion]

What I am getting is a really bad pinging at high RPM, and it literally sounds like the rocker arms are loose and just flopping around. Sometimes the car feels like it has absolutely no power at high RPM, again, as though the timing is retarding more than normal at high RPM (4000-4800rpm).

[Ryatt-Motion]

No other takes on this?

Another thing I have noticed about my car is the sound of the engine, comparitively speaking, it sounds somewhat louder than the other cars, in that, the engine sounds a little like a diesel, and is not as responsive as my 2002's.

I felt a little industrious this weekend, so I took the air filter off and found that it had a bunch of debris in it, so I cleaned it out and then cleaned the MAF with some MAF cleaner. I noticed that there was a thick film inside the throttle body, righ around the blade, so I popped it off and throroughly cleaned it with some choke cleaner and reinstalled it. The engine sounds a little better, but still sounds loose and diesely.

[knightmarez28]

Diesel as in louder knocking like sound? Where exactly is it coming from, upper end or lower end of the engine? As far as oil goes, I'd recommend using 10w40, slightly thicker for all season use w/ your mileage. I say, for the time being, take off your valve covers and check for any damaged/broken springs (sagging, excessive movements etc) as a light check. I'm still looking for info on how to test the springs, the specs etc just incase it is the springs.

[Art Vandaley]

x2 on noise check, does it sound more valvetrain or bottom end?

[Ryatt-Motion]

It is definitely soming in the top end. I was using 5W 30 Mobil one, but have transitioned over to 10W 30, and was going to actually run some Lucas oil it in addition to the 10/30. The noise actually sounds a little like a lifter bleeding down, and there is a slight miss in it at idle. I will try and post a vid of it for a sound clip, so you guys can hear what i am talking about. The noise totally sounds like it is coming from up top.

[Randy L]

Granted this is for my LT1, during my research in getting acam & springs, I found out that stock springs--even the LT4 springs had serious float above 6000rpm. There just isn't enough tension on them to close the valve fast enough at that high an rpm. Not sure about the LS1 springs, though.

[m6speed]

my 02 had a horrid valvetrain tapping noise but it still pulled hard, i used german castrol 0-30 to quiet it down some until i swapped out the lifters/rockers/pushrods and its gone now.

you do not have valve float. you said you have bad 02s? change them, you could try having someone log your car to see if you are lean or rich which could cause your problems of not pulling as hard and pinging.

[knightmarez28]

5w30's way too thin for 90+k miles, I'd strongly recommend 10w40, they're self-adjusting roller rockers, right?

[Ryatt-Motion]

Tony, the car has a strange condition in it where it feels like when I accellerate, it feels as though sometimes the power drops, but then picks back up. When I accellerate hard I can hear the the pinging and rattling in the top end.

Knightmare, the car is bone stock even down to the timing chain. 93,5K, so I should switch over to 10w 40? The car is due for an oil change, so I will flip that in.

Tony, did you change the cam when you did the above?

[m6speed]

Originally Posted by Ryatt-Motion

Tony, the car has a strange condition in it where it feels like when I accellerate, it feels as though sometimes the power drops, but then picks back up. When I accellerate hard I can hear the the pinging and rattling in the top end.

Knightmare, the car is bone stock even down to the timing chain. 93,5K, so I should switch over to 10w 40? The car is due for an oil change, so I will flip that in.

Tony, did you change the cam when you did the above?

yeah i did heads/cam, when i did that i changed the rockers, lifters, pushrods because i wanted to make sure i got rid of that tapping valve train noise. as i accelerated it tapped faster, it wasn't piston slap. i used yella terra ultra lite rockers and ls7 lifters.

try changing the 02 sensors first, clean the maf/throttle body and see if that helps, if not then try pulling your valve covers and checking your pushrods and rockers, make sure none of the pushrods are bent(if bent they would cause tapping noise and loss of power). make sure rockers are all good. what octane gas are you using?