I know this topic has been discussed thousands of times for this car, but I have yet to find a video of a noise that matches mine. I’m stumped and looking for help after looking through many other threads and trying several tests on my own. I’ll try to be as descriptive as possible. Any help would be greatly appreciated!

I have a 2003 Corvette with a stock engine and only 32k miles. I bought it at 28k. It's been driven well, never tracked, and never driven too hard besides the occasional pull. The car has run perfectly the whole time, never even the smallest problem.

Here is the timeline: I washed it early in the afternoon and drove it to an event soon after. I parked it with no problems during the drive, as usual. When I got back into the car a couple of hours later, the revs were bogging down and it sounded kind of like a misfire. Then, sporadically over a minute or so, it went away and worked its way back up to normal. I thought everything was fine then: no lights on the dash, and the idle sounded totally normal. I drove maybe 5 miles to dinner and parked for about an hour or two. When I got back to the car to start it up, it wouldn't turn over, just cranked and cranked. I tried twice, the first attempt was short, maybe 2 seconds, and the second one longer, maybe 5-10 seconds. On the third try, it finally turned over but had a really bad, loud ticking or knocking noise, so I stopped it immediately. I noticed right before stopping that the oil pressure was totally normal at 40. I found a P0200 code using the built-in code reader.

After looking it over, I decided to drive it home slowly as it was only 7 miles away and getting pretty late, never going past 2k RPMs, so I could diagnose it in the morning. No major problems occurred besides the obnoxious ticking noise. I haven't driven it since then.

I poked around with a stethoscope and couldn't pinpoint where the noise was coming from; it sounded loud all over but seemed loudest from both rocker covers, front to back. I decided to pull the rocker covers and check out all rockers and valve springs. Everything looked fine: no play in the rockers, all the springs looked good, and the pushrods all looked centered in their holes. I tried cranking it without the fuel relay and feeling the rockers while they moved; they all operated very smoothly and to their proper depths. All the exhaust bolts are still there and tight. All the plug wires are pushed all the way in. Oil pressure is normal when running, and no codes have shown up since the initial P0200. I attached a video showing the sound as it ran with the valve covers off. The tick goes faster with the RPMs and doesn’t skip a beat even at higher rpm (I haven’t gone past 3k since it started). It also doesn't go away when warm and starts immediately on start.

Video:
I’ve worked on lots of cars in the past, and I am okay with tearing the heads off if it is the lifters, but only if I’m certain of the problem. I’m stuck here and can't pinpoint what the source of the tick could be. So I'm coming here to see if anyone has heard anything similar or has any ideas for other tests I should run. Anything helps!
Thanks!

 

Man, did i just see what i thought i saw, or was that my shrooms kicking in.

 

I l don't see any oil flow coming up from the lifters and pushrods into the holes on the inboard side of the rocker arms while the motor is running. You should have a substantial amount of oil coming up into each rocker arm to provide lubrication to the rocker arm fulcrum and cool the valve spring. Are you sure you have adequate oil pressure?

 

I had to shoot each of these video clips spread out over time on cold starts because the oil would pick up very fast and start creating a huge mess if I let it run for longer than a few seconds at a time. I have made sure that each pushrod has oil coming out and that my oil pressure stays normal every time I had to start it.

 

I had a lifter seat (the part that upholds the pushrod) fail in my 2000 Blazer and it sounded just like that. The noise was the lifter bouncing against the cam because there was no longer the proper pressure being applied to it.

Can try to take the rockers off, and the pushrods out and peak down the hole to look at the seats of the lifters. Will be hard to see, but possible.

 

Could you feel any slop or slack in your rocker when your lifter went bad? All of my rockers feel super solid with zero play in them. I would imagine that if the lifter seat was bad, it would translate up some slop to the rocker, but I could totally be wrong in that assumption.

 

I don't recall as it was 6-7 years ago. I remember the pushrod sank about another 1/4" into the lifter when the seat failed. So it's possible that there was still plenty of tension on the rocker and pushrod to feel like it's in good shape.

 

Stethoscope $5 harbor freight start poking

 

Is there any way to measure oscillation speed of the noise? If it matches the idle speed, then wouldn't the problem be somewhere on the crank rotating assembly? If it's half the idle speed, it would be on the cam/valve train.

 

Based on the slow-mo videos I took it seems the noise happens twice for every one valve movement, which would point toward bottom end. The strange part is the tone of the noise, it sounds higher pitched than a bottom end deep knocking sound, it's also very consistent in sound where knock sounds more random kinda like it changes from stroke to stroke. I pulled fuel to every injector one at a time and with every one it bogged down a little and the noise stayed just as consistent and loud.

 

Re-read your post. Try stethoscope on fuel damper. Try running fuel system with engine off. Mech pressure on rail during test.

Remove all plugs and crank the engine over with high power battery high voltage so the engine spins fast. Verify fuel pressure. See if ticking present or not. Try cranking with and without fuel pressure.

The weird no-start is kind of a fuel system clue. But rpm dependent? How is that possible. Once per revolution like a bolt sticking out somewhere. Inspect flyflex visible bolts. But that won't cause no-start either. Seems to run normal. Its not a waste spark so every tick can't be a plug.

Hmm I'd put a fuel pressure gauge mechanical on the front of the rail while running fuel system, crank engine both run and with plugs out, check what the fuel pressure does, if it pulses or something weird.

This is a strange problem when we assume the ticking has something to do with no-start condition. There is apossibility of this being a coincidence, however.

 

Perform a compression test while plugs are out. Use high quality tester. DO not rent a tester. If a cylinder has low compression it will dramatically assist diag.

I Remember one engine a long time ago with low mileage had some rusty injectors, and one of them got stuck open a bit and flooded a cylinder, making it bog like that. Then it kinda ran okay for a bit and did it again, filling the cylinder while it sat and hydrolocking the engine a bit bending a rod so the crank counterweight was smashing the bottom of the piston.

Your def gonna want to compression test and review the plugs and look at the injectors maybe have em sent to be cleaned. See what they look like on the bottoms.

 

Sounds like crankshaft speed on the ticking to me also. Is the harmonic balancer wobbling? Cracked flex plate/flywheel maybe??

 

The thing is, the car bogged then refused to start. I ask myself, What does bogging and refusing to start have to do with parts ticking? If we assume those are connected, it cant be a balancer or a cracked flex or bolt or accessory etc... because that wouldnt cause bogging and flooding or lack of spark/fuel to start. The only way I connect these is beginning to think it flooded couple times and the problem is related to a bad injector or corroded ECU connection wire somewhere that filled a cylinder and bent a connecting rod. how else does fuel cause a ticking noise every revolution on a sequential EFI engine? Compression test might not even show a definitive answer but its my next suggestion with the stuff I mentioned.

The tick does sound very top-end ish. But being not in the valvetrain how does that work? Whats at the top of an engine that ticks that isnt the valvetrain? Fuel damper? Ah just rehashing what I already said. Its a mystery and a half Im very curious , tick tick tick if you had HPtuners you could disable 1 cylinder at a time , but plugs out cranking fuel on/off is the next diag for that

 

The best case is you find a bolt , balancer or accessory or transmission component making the ticking noise, and the no-start bogging was completely unrelated and the engine just needed a tune up and a clean air filter/maf.

 

I keep hoping that is the case!
I will run the fuel and compression tests this afternoon and I'll make sure to update with what I find. Thank you for all your ideas!

 

Ok here is the results from the tests I ran.
Fuel pressure car on not running: 52psi stable
Fuel pressure at idle: 62psi very small variation but pretty stable
Stethoscope on fuel damper: No out of ordinary noise
Fast cranking without plugs: Couldn't hear ticking over starter
Plugs look fine no signs of out of ordinary wear
Compression tests:
1: 162
2: 185
3: 170
4: 175
5: 167
6: 175
7: 141 (ran many times same result)
8: 184
Cyl 7 doesn't look too great but let me know your thoughts on that. Unless there are any other tests I could run I will put the car in the air tomorrow and check under the flywheel inspection cover to see if any bolts on the clutch or flywheel could be the source. After that I will likely begin to disassemble the engine to get the heads off and continue the search for the source.

 

Those numbers are kind of all over the place. Did you try a second compression tester to verify? Is the tester you used a high quality known-good tester? They go bad all the time when people forget to let the pressure out.

If we assume the test is legit then I would
1. Put a cap full of light engine oil into the low cylinders to see if the numbers improve when cranked with some oil in there. It would help with ring sealing and give you some direction.
2. The super low one 141, try cranking with all plugs out except that one, leave that one in, see if the ticking noise starts with just that one plug installed.
3. You could try putting just 1 plug in 141 and run just that cylinder, e.g. unplug all injectors except #7 and let it fuel/spark to see if it ticks during cranking when that one cylinder fires.

When you crank the engine without any plugs, in the cylinders with no plugs make sure there is no fuel going in. Either unplug injectors or the crank trigger or disable the fuel system (remove the fuse) you don't want to spray fuel into a unlit cylinder okay.


Fuel pressure: 62 with car running : Doesn't make sense. Fuel pressure should not rise when you start engine or any other reason on non-ref fuel system.
Your test could be wrong. Or this could be a massive clue to some issue with the hard starting or ticking noise. I would figure this out before pointing fingers anywhere else. Again always double verify your result when its weird. This one is very weird.
In this case I'd want to see fuel pressure while driving. And see why the pressure is so high, I wonder if the report is wrong, or, there is some return line clog, or some issue here. I'm not sure how it contributes to ticking noise though.

Another thing youll want to do is inspect the #7 fuel injector for corrosion, inspect the #7 intake manifold port for excessive oil or abnormal markings on the valve, the valve of #7 should have a fan-like spray injection pattern like the rest, look for signs of it being washed with fuel cleaned of carbon .


Ok lets talk about the low compression now a bit more
The cylinders being all over the place suggests carbon buildup on valves. It might just be valve build up unrelated to your ticking noise, so you will desire a leak-down test to find where the air is going. The leakdown test is difficult to perform sometimes for people so I don't like to just say "do aleakdown test" like its so easy, but in this case I think you really need to do this test now, see where the air is leaking out of these cylinders, especially #7. It its going down into the crankcase more than the other cylinders it should produce flow out of the dipstick you can tell, feel, or hear, remove the dip stick and listen/feel for airflow from the cylinder. Make sure the crankcase is sealed up tight it could leak out somewhere else like the oil cap or a broken valve cover gasket or something so watch for oil forming drips. A better method would be to measure the crankcase pressure directly if possible but you'd need a gauge with inches of water resolution for the 0.5 to 3psi range of detection inside the crankcase.
In these days it also pays to bore scope. I would go in with a scope and look particularly at the in-the-hole-depth of the #7 compared to others, look for ridges on the cylinder walls that indicate the piston isn't moving its full sweep range of motion anymore. Look at the valves see if they seat. Its a shot in the dark but its worth doing if your considering pulling heads off a low mileage engine that might just have a little carbon buildup.

Also now that you've got a finger to point at #7 pay close attention the valve motion while the engine runs - make the camera show in slow motion the valves whether they both close fully or not. Perhaps the ticking is a valve sticking open and then getting slammed shut by compression on the next stroke, tick tock tick tock tick tock easy fix.

Finally if all these tests fail you could try engine ingest seafoam to clear out some of that carbon. Do what the instructions on the can say exactly, precisely, its like feed seafoam, then shut engine off let the seafoam work on the valves, then start again. You can repeat this kind of test a few times to see if those compression numbers come back.

Don't be hasty to rip everything apart when the engine still runs fine, patience

 

Update:
The source of the tick is a bent connecting rod in cylinder 7. The noise was coming from the piston skirt right below the wrist pin hitting on the crankshaft counterweight. See attached images.

To find the noise, I went ahead and pulled the oil pan (not fun by the way) and saw that number 7 had a slight bend in the front to back direction, that led me to remove the heads to pull out piston 7. When I removed it I found the bend in the up down direction to be much worse (as pictured) than the bend in the front back. I found a small scrape under the wrist pin and believe that is the source of the sound. I inspected all around the counterweight looking for damage from the impact but couldn't find anything more than the smallest scuff where it rubbed at bdc. There is no damage to any other part of the crankshaft and there is no wear to the bearings or mating surfaces. The reason for the tick tock sound must be the difference in pressure between intake stroke and power stroke.

I now have to diagnose what caused the hydrolock in the first place. Due to the low miles the oil trail on the intake port tells a story, when comparing the oil residue from intake port 7 to the rest you can see the sharp perfect spray pattern on all the rest but on 7 the line is much softer with oil grime going further in. This makes me think this injector had a bad spray pattern in the past and likely finally just gave up and failed flooding the cylinder. I attached a photo of intake port 7 (in the back) and 5 (to the front) to showcase what I'm referencing.

The two options are electrical failure or injector failure and given the assumed spray pattern and overall likelihood I am lead to believe it was a injector failure that caused the hydrolock. If that is the case I will replace all the injectors with new likely aftermarket injectors to prevent another failure in the future. Advice on good injectors would help, not looking for power adder just similar spec to oem.

 

Damn. I'm sorry I really wish I was wrong.


The most likely way to succeed going forward is,try to find brand new injectors from directly GM somehow.
Do not buy aftermarket or ebay or amazon injectors, they are counterfeits almost always.

However you will want a complete workup diagnostic on the wiring / ecu / injector plugs.
You will also need to send that bad injector out to someplace for testing. If they directly tell you that it was bad, doesn't close properly, etc... then good that will aid your diag. Still, keep looking.

You don't want this to happen again.
Steps to take , lets think about this carefully,
1. Remove ECU plug and inspect pins for corrosion on BOTH sides of the plug, AND inside the ecu. Look under the insulation if needed, remove tape or whatever is in the way you really need to see a nice clean connection from ECU to Plug-wiring.
2. Inspect injector plugs for corrosion. Look deep inside the plug. Perform a touch continuity test 'poke but not scratching test' where you take a sharp tester and poke the surface of the exposed metal to make continuity. A lack of continuity on the initial 'poke' is a kind of sign there is some oxidation or corrosion forming a layer between your instrument and the metal conductive surface.
3. Visually see if you can confirm the injector looks bad or wrong , probably not but might as well take a picture and record.
4. When you get new injectors, do your best research, pictures, part numbers, etc... to verify they are legit. Look for GM casting information in them and compare to old or other injectors. Spend extra time verifying the injector quality.
5. Consider sending your brand new GM injectors out for testing. Its risky just to do this but if you have a local place you trust or a very handy protective shipping method it would be fine I think. You really really wana confirm injectors before they go in if possible. Even if new, from GM. In todays world it kinda stinks but thats where we are. They dont make em like they used to is holding.
6. Ok new injector installed, see if they hold fuel pressure. You might be able to run the fuel system full pressure and hold the injectors out so you can visually inspect and smell for leaking. When you shut off the fuel pump the pressure usually stays in the rail for a while on most cars with stock-ish fuel systems. There is a check valve in the fuel pump usually. And the regulator should hold clamped tightly, holding pressure. If the pressure is leaking out you need to find where its going.
7. Finally and most importantly and overlooked frequently - you should perform an injector continuity test from the ECU into the injector plug and out the other side. Put one end of the tester in the ECU plug that leads to an injector, and put the other end of the tester on the other injector wire coming out of the injector plug. The continuity will show the resistance of the injector (10 or 12ohms usually maybe 14) but that is not what you are looking for. Wiggle the injector plug/clip and wiring to see what the continuity does. It should never lose continuity while you jostle the connections. There is a possibility of a corroded or bad/worn injector clip, as silly as it sounds, that will break and make continuity when touched or vibrated. This is something I always do when installing new injectors/plugs because I find sometimes the brand new plugs or clips don't make good connections and this leads to all kinds of weird misfires and breakups etc... This is also a way for you to test the connection at the plug down by the ECU, wiggle it as well, play with the wires, try to get them to screw up.

For cleaning purposes obviously
A. Wash the intake manifold completely several times. Oil tends to stay lodged deeply. Degreaser like purple caustic hand melting solution or simple green is good. Submerge for a while if possible.
B. Wash and wipe the intake port of the head. Try to clean it up with brake cleaner. You can remove the spark plugs to avoid and hydrolock when cleaning. Never let water or air contact cylinders for longer than about 10 or 20 seconds it will rust quickly, you can remove the head anyways and just wipe it with oil and some mineral spirits will help break up carbon around the rings and piston.

For the pcv system, make sure it is well maintained. PCV is the most important system on the engine. Use a brand new pcv valve from GM, not aftermarket. Replace the pcv hoses with quality hose, not random hose. Use OEM pcv hose designed for the pcv system if possible because you have a stock engine it should be kept as original as possible this way. Make sure the crankcase is fully sealed, no leaking, you can blow into the crankcase through the vent hose and see that it holds pressure or find some leaking. It should hold 1 or 2psi easily for a while and release when you let your finger off the hose. I have a video if you'd like.

That should get you started seems like you know what you are doing. Pulled it apart pretty damn fast I'm impressed. Just remember if the engine gives you trouble for re-assembly, or machine work is done wrong or taking too long, you can always get a high mileage reliable replacement engine for very affordable, an L33 (05-07 5.3L Aluminum) is damn good solution to a blown expensive engine time constraint syndrome.