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http://www.youtube.com/watch?v=fkW14...ature=youtu.be ***

I've been away from the forums for a while as the car has been running great for years. I have a 99 Z28 with 50-something thousand miles on a stock motor. Mods are nothing more than full intake and exhaust. Car always gets mobil-1 and 93 octane at every fill up. Regular oil changes and never raced, only the weekly spirited ride. I did have a rocker arm spew its bearings a few months after I bought it (years ago) but I immediately fixed that and its been running great since.

I was driving home today and was nearly home, sitting at a stop light. I noticed the rpm's dipping and the car wanting to stall. I dropped it into neutral to keep the rpm's up a little, and limped it home gently (just another mile down the road). The car never did die, and I got out to listen. After some investigation I noticed a new noise coming from the driver side valve cover area. My mind immediately went back to the rocker arm issue i had early in the car's life. I pulled the valve cover and found nothing obvious out of the ordinary (to my untrained eye that is...).







So I took a video for you experts to review for me. This is the noise its making now. If anyone has any recommendations as to what my next move should be based on the noise in the video I'm all ears. Should I just take it in, or is there something else I can do to inspect further...?

http://www.youtube.com/watch?v=fkW14...ature=youtu.be

---Night two---- more info ---- vaccum test

The noise in the video is not at all present when the car first starts. It take a minute to appear. The pattern I have noticed every time I test is that once i put the engine under a little load and let it idle (specifically, turning on the air conditioning while at idle) the tick in the valve train area becomes evident. I had a vaccum gauge on it tonight, and before the noise becomes evident, there pressure was steady and normal. Once the tick begins, the vaccum pressure will dip with each tick of the motor.

Once the motor warms up the tick is there to stay. It becomes more steady as the motor gets up to temperature. It will not go away again until the motor cools.

Keep in mind that as far as i can tell the car only seems to struggle at idle. Hard to say whether the tick is evident or not. In all honesty I dont really care to take it out and rev it around at this point for fear of doing more damage.

 

Anyone have any ideas? Recommendations?

 

Sounds like a valve train tick to me. I would remove the drivers side valve cover and disconnect the passenger side coils. Have a friend crank it over while you watch. Also check for any loose rocker arms or loose pushrods (ie: no lifter preload). Sounds like you have a dead cylinder in addition to the noise from what I can tell in the video, likely related.

 

Can you provide more detail on what I should be looking for? Just anything in the valvetrain that doesn't look "normal"?

When you say it sounds like a dead cylinder, are you thinking a cylinder that has somehow lost compression? Or one that is not getting fuel or spark? Or maybe that is an impossible distinction to make from just listening to a youtube video... ?

I can provide just a little more detail. I did break out the vaccum tester tonight (too exhausted to do much of anything else). Here is what I found.

The noise in the video is not at all present when the car first starts. It take a minute to appear. The pattern I have noticed every time I test is that once i put the engine under a little load and let it idle (specifically, turning on the air conditioning while at idle) the tick in the valve train area becomes evident. I had a vaccum gauge on it tonight, and before the noise becomes evident, there pressure was steady and normal. Once the tick begins, the vaccum pressure will dip with each tick of the motor.

Once the motor warms up the tick is there to stay. It becomes more steady as the motor gets up to temperature. It will not go away again until the motor cools.

 

This is my best guess listening to a youtube video so be sure to troubleshoot it yourself and see or find the problem before you start replacing parts.

 

It seems I found the problem. Loose spark plug wire on the plug side (driver's side, 3rd cylinder back). I can't figure out why it was dependant on temperature, but it was. Anyway, I was going to switch the coilpacks from left to right, and as I did i was pulling the plugs wires off the plugs. The third back on the driver side came off way too easy. Put everything back together snug and it has been running like a champ - took it for a test drive and everything, no more ticks.

Hope that's the end of it!

 

I can't tell if I have the same thing going on or not since I just did a **** ton of work but I already rechecked my entire valvetrain twice (correct pushrod legnth, rockers all torqued, springs all good)

When you were driving was it alot more constant and is it loud enough that you thought it was mechanical, can't really get the true volume throughthe computer.

I'm waiting on new wire now, and have to grab my buddies coil to help eliminate.

But same thing doens't happen until its hot and there is a load. Also no CEL

 

Funny I listened to your video and was going to post up sounds like a spark jumping from a plug wire and I seen your update. Good easy fix.