Name My Engine Noise!

[ThisIsSparTTa]

Hey guys, so I know a couple of you may have seen my previous posts, and for my Z it's one thing to the next.

A quick synopsis although I doubt it matters for this issue: replaced spark plugs (PFR6b-11B gapped @ .035 per Greg at SZ due to 14PSI boost), replaced injectors (740CC), new SZ ECU, replaced valve cover gaskets, deleted EGR/AIV, deleted plenum water hoses, troubleshot a huge air leak that ended up being an o-ring in a bad place on an injector

So, after being down for 3 months and overcoming several hurdles, I finally got ALL SIX cylinders firing, and man was I stoked! Pulled her out of the neighborhood and noted to friend the lifter tick that was already there previously. Took her for about a 20 minute drive around, and the lifter tick sounded a bit louder than I remembered, but I hadn't driven her for 3 months, and I only had her for 3 months before that so I figured maybe it was in my head. By the end of the drive, it was becoming apparent it wasn't lifter tick, we pulled off, popped the hood and the engine had a terrible knocking noise at idle which definitely wasn't there before. It follows the RPMS as you will see below, and seems to be on the driver side and loudest at the exhaust valve cover via a mechanics scope. We left off and drove another mile or so, the noise was getting worse, sounding like I was dragging cans behind the car, and as I pulled up to a light the engine just cut out, didn't stumble and die, just cut. I've been having battery issues and haven't gotten a good charge on the battery due to not being able to run properly (I may also have a bad battery), but anyways, after 4-5 cranks it was obvious the battery was dying and we weren't starting. Pushed off, tried to get a jump. I've jumped it off probably 10-15 times due to running battery off and then while I was working on her due to not being able to charge it, and it always started really fast. Refused to jump and basically started to refuse to turn over much at all. Had her towed home. Finally tonight with the assistance of a battery charger I got the starter to run, but wasn't firing. I put the charger in starting mode, and the engine finally returned with the same noise. Enjoy a couple of videos below and shoot some opinions please!

[youtube]http://www.youtube.com/watch?v=kT8gmlimxJg[/youtube]
[youtube]http://www.youtube.com/watch?v=mfw2CW7vqIg[/youtube]

My friend helping me said he had heard that noise before on someone else's Z and it was rod knock. After doing some searching and watching youtube videos I've seen other people suggest things from oil problems to timing belt issues. I took part of the drivers timing belt cover off tonight and the belt right there was very tense and looking like it was in good condition. I will probably properly take it off tomorrow and get a better feel for the tension.

[t.mcginley.jr]

Sad to say it, but that sounds very much like rod knock. Lifter tick would be faster than that and not as loud. Probably spun a bearing or something. Someone else might know better though

[Ziggy1621]

Could just be the video, but sounds higher pitched. /\ he is right... it's too slow for a lifter, I'd be worried about a bent valve not closing all the way and contacting the piston. Sounds loud on the video which makes me think it is a top end noise. Your timing may be off.

[Ace2cool]

Yep, definitely one of those two things. The first video sounds like rod knock for sure, but the 2nd video makes me think timing, because when you revved it, the noise changed. Sounded like the timing advancing changed the sound.

Did you do a timing belt job recently? Sounds like it could be off by one tooth, allowing the valve to make contact with the piston, as Ziggy said.

[ThisIsSparTTa]

Timing belt was done roughly 20k ago. Nothing I've done since I've owned the car should have affected the timing belt, and in theory if a proper 120k was done, then the tensioner etc should have been replaced, so I shouldn't have a problem. However, tomorrow, or at worst, Sunday, I will be checking out the timing belt and timing a bit closer.

Also the videos are "out of order" with respect to time. The top video was actually taken after I got it towed home, etc, where the sound is very consistent. The first video was taken before the tow, and although harder to hear (why I took a second video), they sound was a little different. It's hard to put in words, but it was more of a pattern of *loud* *mid* *soft* taps repeated over and over. It followed the higher RPMS but also added in some nasty other sounds knocking around.

[Ziggy1621]

The fluctuating noises lean toward timing

[Chattzx]

That's 100% a spun bearing, sucks man, I've been there and done that.

[Ziggy1621]

100%? Hmmm

[Chattzx]

100%? Hmmm

When mine spun a bearing it sounded exactly like that, so yeah I'm pretty positive. Disconnect the coilpacks individually to see if the noise goes away thats a pretty sure fire way to tell.

[ThisIsSparTTa]

Why would disconnecting the coil packs help? Isn't the rod/cylinder going to keep moving along with the rest of them whether or not the cylinder is actually firing? I can try it once I get the front of the engine back on here in a few days.

As a quick update, pulled some of the front of the engine off to get both of the timing belt covers off. All 4 sprockets line up properly with their timing marks. The belt seems tense everywhere I can push on, and I don't see any suspect missing teeth or other. You guys think its worth the effort to get the lower timing belt cover off so i can check the last mark? I haven't seen anything so far to make me think the timing belt could be an issue. I plan on checking the timing itself in a few days when I get it back together.

Side note: my fan was centimeters away from fully cracking through, so I just ordered a new one. I could put it back together for the moment with the bad blade, but will wait until it comes in so I don't have to pull the radiator again.

[Ziggy1621]

Funny thing, I had a fan that was cracking, and because it was unbalanced, sounded li,me a rod knock. Don't think that's your issue.

Did you count he teeth between marks? That's the best way to tell if timing is correct.

[ThisIsSparTTa]

Alright, so I checked the timing marks, and they all lined up properly and the timing belt was tense in all locations and I didn't see any bad teeth or anything like that on it. I performed an oil change and went with 20W-50 this time with also STP Oil Treatment. Put it all together, including my new fancy bright white fan blade.

First crank attempt, then engine started, but died in under 5 seconds on a pretty bad series of sounds. 2nd crank attempt it cranked right up, with our knocking noise ever present. I let it idle for about 5 minutes hoping that some of the new oil or oil treatment would circulate around and possibly fixing any stuck lifters or similar. While I was doing this I also did a manual power balance test and the clicking always remained. I took out the mechanics scope, and really the ticking is kind of present on both sides, its a bit hard to tell. Under the car I stuck the mechanics scope to right behind the crank pulleys and the knocking was very loud there. This kind of makes me want to still think rod knock/spun bearing.

Anyways, last thing I have to do is check timing, and I should be borrowing a plug wire to use today to make that a bit easier. I'm kind of doubting timing will be an issue, but I guess I'm willing to try anything reasonable before giving in to a blown engine.

[ThisIsSparTTa]

Update for anyone searching in the future since I've already been pinged on this a couple of times. Finally got the engine apart, opened her up, and sure enough cylinder number 4 had a spun bearing. I should be getting my new short block from Kyle @IPP next week and hopefully have this thing back on the road by the end of the month!