Engine sounds like a bag of marbles

[kurthutchinson]

Today, I took my S4 to run errands, made my first stop, for two hours. Came outside, started the car and it sounded weird.. like marbles. Then I saw the CEL and EPC light on. Hopped out because at first it sounded as if the cooling fan was making contact with something. The engine felt like it revved freely, and the weird lud noise would dissipate and as revs increased and then come back.

It wasn't but the noise was immense from the front of the engine, but nothing felt like the noise I heard. I knew better than to try and drive the car, and I happened to have a CARLY scanner in the car with me, it came back with P1519. So I called for a tow and started trying to understand what just happened. There was nothing really leading up to this, it was almost binary in nature.

Anyhow before the tow truck, I tried starting the car again (ironically to get the recording on this link) Audi Noises Now it sounded really bad and some harsh vibrations were felt, and the car sounded like it struggled to start, much slower turning over than normal.

When I got home, I ran VCDS lite, to get all the codes. and I was presented with:

VCDS-Lite Version: Release 1.2
Friday, 02 December 2022, 21:38:43:46511


Chassis Type: 8D - Audi A4 B5
Scan: 01,02,03,08,15,16,17,25,35,37,45,55,56,57,67,75,76 ,77

-------------------------------------------------------------------------------
Address 01: Engine Labels: 078-907-551-AZA.LBL
Controller: 8D0 907 551 M
Component: 2.7l V6/5VT G 0002
Coding: 06711
Shop #: WSC 63351
VCID: 341B2A7C1723
3 Faults Found:
17927 - Camshaft Adjustment; Bank 1: Malfunction
P1519 - 35-10 - - - Intermittent
17755 - Camshaft Position Sensor 2 (G163) / Engine Speed Sensor (G28): Incor. Correl.
P1347 - 35-00 - -
16730 - Camshaft Position Sensor (G163): Implausible Signal
P0346 - 35-00 - -
Readiness: 0000 0000


So my question is, where do I start? Is this really indicative of needing to just replace the Cam Chain Tensioners? or are the Camshaft position sensors bad too?

[Silverex]

I bet a cam chain tensioner/pad failed. Pull valve covers and take a look.

[ShelbyM3]

I’d start by pulling the valve covers, also. I’m also suspicious your tensioner or tensioner shoe failed and you may have some damage in there. Small insurance, in my opinion. If all checks out, then go to sensors. I have a feeling you won’t be too concerned about the sensors, though.


Sent from my iPhone using Audizine Forum

[Monty23]

CCT pad got eaten for sure. Make you pull the lower oil pan and clean all the plastic debris out and clear the oil pickup. Just buy new pads online, don't replace the whole CCT with the crap $400 ones.

[kurthutchinson]

Welp.. After taking apart the top of the car to get to the valve covers, and discovering everything looked taught and no damage visible. A friend asked me about my timing belt (which I changed back in March). So since I wasn't in service mode, I was able to loosen the passenger side of the cover just enough to get a peak. Looking inside, the belt looked sheered and it was essentially loose. So I'm not sure if the tensioner gave out, (which I changed) I essentially used the ECS tuning Gate Racing timing belt kit to do this job back in March.

So.. hoping that there isn't some bad damage from my assumption that the car jumped timing. Will being getting into service mode to pull everything off the front this weekend.

Loose timing belt




Obligatory video of the timing belt.

[Silverex]

Its no uncommon for the idler pulley bolt to break that comes with timing kits. That would be my next guess but from the video I don’t really see any damage on belt and hard to tell if that much slack is normal......I’m always surprised how much there is.

Regardless I’d still pull front end to get a better look at everything

[Monty23]

Sometimes the hydraulic tension just compresses. I've had this happen a few times and its never caused me any damage even though I would see slack in the belt. When this would happen, I would replace the hydraulic tensioner.

[Maker]

I too have had the tensioner bolt sheer causing a loose belt and bent valves.
It seems the bolts that come with the kits are sometime low grade.
Now I use only chrome molly bolts.

[waveblaster200]

Maker do you have a link or a source where to get the chrome molly bolts?

[Monty23]

I get the class 12.9 bolts from mcmastercar to replace these.

https://www.mcmaster.com/91502A401/

[kurthutchinson]

Latest update.

So over the past week, I've boroscoped the engine, (didn't see any evidence of valves touching any pistons), due to what i thought was a positive sign. Proceeded to the next step of figuring out what happened and doing another timing service.

Upon pulling the timing cover off and inspecting, you could see the bolt holding the timing tensioner had sheered off, you could just pull half the bolt out as it snapped. So, no problem got the remaining bolt out, replaced with the new tensioner and belt from the continental kit, and set timing, base on how the cam sprockets looked, it appeared to be off by one tooth (on the drivers side).

After getting all the belts and stuff in order, doing a valve cover job to replace gaskets on the drivers side. Started the car to see if everything was good.

I got a very weird start.. Smooth in some ways, but seeking idle all over the place like a vacuum leak. With that just from that perspective the car seemed hesistant to rev, but wasn't shaking etc.

So pulled the plugs and did a compression test. The passenger side showed 160 160 170 (going from firewall forward), The drivers side showed 0 0 0, if there were bent valves would that be expected across the board? Something doesn't add up, and I feel like I'm missing something. Before I go investing in new head, or possible engine swap. Is there something else that could cause the entire drivers side to show no compression? Also one other interesting symptom, while running it also sounded like a pop. Almost similar to the sound an NA car makes when revving. But this happened while idling, almost like pressure was building up somewhere and releasing.

*Note I didn't run VCDS-lite as I forgot to bring laptop and cable to where I was working on car (friend with heated garage), but his Autologic only expressed misfires.

[S4James]

dude you fucked the valves on that side. I know because the exact same thing happened to me. tensioner bolt sheared, marbles, no power. mess. Rebuild time.

[Monty23]

The passenger side showed 160 160 170 (going from firewall forward), The drivers side showed 0 0 0, if there were bent valves would that be expected across the board? Something doesn't add up, and I feel like I'm missing something. Before I go investing in new head, or possible engine swap. Is there something else that could cause the entire drivers side to show no compression? .

Think about it, the cam controls the position of the entire bank. When slack in the timing belt causes the cam timing to be off, it only takes 2 crank revolutions for the 4 stroke cycle to complete. At 800rpm (idle) there are 13.3 revolutions per second -> doesn't take long...

[kurthutchinson]

Yeah, I get it, that it might be bent, the timing was off by what appeared to be one tooth on the drivers side.

Anyways for some details.. and the sounds.. check this video: https://www.youtube.com/watch?v=xvzoaZ-64lA

[Silverex]

Bro you 100% bent valves, it’s clear as day they hit the pistons.

New engine or at very least head(s) and clean sharp edges off pistons and send it.

[kurthutchinson]

So the story gets more interesting..

After cobbling the car back together, I had to drive it home. Car was backfiring like mad, so I was preparing to park it for a while as the local Audi tuner shop I trust couldn't take the car in until Jan 29. (I'm not quite comfortable with doing the Head/Valve job).

Anyhow.. yesterday I had to move it to get my driveway clear so my wife can get in and out. Start the S4, and no back fires, but I notice the misfires at idle, but stops at 1500 rpm. Decide to drive it around the block, and it drivees normally. Decided to get adventurous (since I consider the car to be dead) and drove it on the highway, drove fine, pulled like it used to. So I was baffled, the check engine light stopped flashing, car was perfectly fine on highway.

So today I go back out to figure what's what. The misfire at idle leads me to think PCV issue or vacuum leak somewhere. Also idle speed is lower than it was prior to all this happening. Took it for another drive, tip computer on my highway drive showed about 25mpg cruising at 80mph. Got off the highway and did some full pulls from a stop and everything felt normal.

Don't get me wrong, I can hear a valve ticking at idle when outside of the cabin of the car.

VCDS shows misfire on the entire drivers side, if the driver's side valve cover wasn't seated properly, could that lead to some issues?

Thanks again for any advice given here.

[Silverex]

If you planned on buying another engine anyway, guess you could drive it until catastrophic engine failure when it drops a valve. You’d just be out a tow and possibly turbos assuming you were going reuse them.

Edit: just saw your new video where it seems like you have false hopes in valves not being bent. To illustrate it here’s a pic of your piston and one of mine during rebuild. The areas I circled you can see had metal on metal contact where the valves hit which means they are 100% bent unfortunately. Could be only slightly and drive ok for awhile but they ain’t going fix themselves and will eventually fail.

[S4James]

Its clear as day in the video.

[kurthutchinson]

Yeah, I mean I still have my appointment here with a specialist. Its not till Jan 29th though, which I assume at that point I can get better direction as to what direction I'm going, whether new head or new used engine. And then if new used engine, do I follow the path of many others with KO4s etc and all the other goodies. Following my channel you'll see I gotta another project I need to complete to fund any of this madness.

Thankfully, this isn't my primary or secondary car, so driving it would be bare minimum as I have to move it from time to time due to street cleaning; as for my optimism, its mainly that the car can move on its own, and a curiosity as to how a damaged engine like that can feel "correct".

[Silverex]

I had a WRX with a chipped valve, the valve head looked like a pizza with a slice missing. Lol
It drove pretty damn well other than some miss fires for a couple thousand miles before tear down. My Avant drove great and during disassembly there was detonation marks all over pistons, rings were so caked up that they wouldn’t move/spin, yet it still made stg3 power with ease. Long story short you’ll be amazed how shitty an engine can be and still run great….until it doesn’t.