I have a 94 Z28. First problem:

When my car is cold, hasn't been driven in a few hours, it makes a tapping/slappy noise when I crank it and drive it. When it warms up, it's fine. It sounds great.

The second problem is that when I've driven it a lot, or just powerbreak it like I like to do, or do donuts like I like to do, my RPMs start jumping around, like the spark plugs aren't firing or something. And that had only been when I was sitting still. Up until today, when I was coming home, and it started doing that when I tried to accelerate at any speed.

It does that when I'm sitting still, and when I try to go, no matter how fast or how hard I give it gas, nothing happens. It jumps around a little bit, and THEN goes. Whenever I get to a decent speed, it runs good until I try to accelerate a little, and then it jumps some more.

My third problem is that my car over-revs before it switches gears. It has always done that ever since I got it. It will run clean into the red and stay there until I let go of the gas a little.

If anybody can help me at all, I'd appreciate it. Thanks.

 

I had a 95 and a 97 and both did this at one time, both times it was a plug wire(s) that had either been burnt from headers or cut via a belt...

 

When my car is cold, hasn't been driven in a few hours, it makes a tapping/slappy noise when I crank it and drive it. When it warms up, it's fine. It sounds great.

Check for a broken exhaust manifold bolt...[exhaust leak]
Or possibly 'piston slap'...



My third problem is that my car over-revs before it switches gears. It has always done that ever since I got it. It will run clean into the red and stay there until I let go of the gas a little.

Slipping trans...

 

It's piston slap.....I've heard thats normal with these engines. My old motor used to do that all the time upon start up.

 

Sliiping Transmission!? Not again!! Geez, I've already had it rebuilt 4 times in the past month. It couldn't be a loose throttle cable (a friend suggested this) or anything, could it?

I can check exhaust bolts and all, if it's not that, then it's not really a big deal since my 93 Z28 did the same thing a few months ago before I slammed into someone going 120. heheh...

And that spark plug wire sounds about right, since my serpentine belt broke and exploded a bunch of things under my hood.

Thanks for all the help. I hope I don't have to lose my car because of that POS transmission AGAIN this month.

 

Hm. i woulda swore i heard only LS1's have piston slap, and not really LT1's.

I would put money on that its one of your rocker arms coming loose. If its a loud tapping noise coming from under your valve covers, thats what it is. The nuts are self torqueing that hold on the rocker arm to the rocker arm stud..and they loosen over time.

If this sounds more like the problem, let us know so we can tell you how to fix it. Good luck man...if it is a rocker arm loosening up, you need to fix it before it throws off the pushrod and you're a cylinder too short.

 

Hmm... does that rocker arm problem go away after the car warms up? Because the noise goes away after it warms up. My 93 Z28 had the same problem, and I ran it like that for over a year and I never had any power loss or engine damage. I dunno, if my transmission doesn't go out for the 5th time, I'll check all this stuff this weekend, and see what's up.