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New Short Block Knocking On 2000

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I bought my boy a 2000 as a learning project.We bought a short block and put it in (wish I would have seen the Seafoam thread!). It only had about 103000 on it but it had a blown head gasket and serious water scale buildup in the head. We cleaned the head and valves up and it ran great after firing it up. It still runs ok, but engine light is on and it throws codes related to cat converter. We replaced both O2 sensors, have a new cat converter on the way.

Problem is a pretty scary knock down near the bottom of the engine. I am hoping this is not a rod bearing or other major failure. Up top it doesn't sound bad, under the car on a jackstand is a bit clanky at the rev rate of the engine.

Worried about the knock we did run a partial can of an engine decarbonizer from OReillys in the oil and gas tank (per instructions). We ran it 60 miles and then had an oil change. Still knocks pretty bad. We have not yet filled it and it is 87 regular octane unleaded gas.

So, thoughts? How do we tell if there is a rod or crank bearing problem. We only have about 2000 miles or less on the short block. We tested the advance solenoid and it seems to work well and be pretty balanced gaps in its 2 stroke positions.

Suggestions? Would the Cat throw off the whole operating mode of the engine enough to damage it or cause this noise temporarily until replaced?

By the way, to get the emission inspection past we soaked the cat in a mild acid bath for about 12 hours. It ran with no light for about a week and then the cat code came back.

Dare we drive it more? I'd like to run it in and get premium grade gas.


Addendum, At least inside the car in park, coming off of idle on the throttle and the sound diminishes or disappears. Driving, it seems to be only when coasting that i hear the sound. decelerating or accelerating it diminishes or disappears, to my ear. Curious.

Could be rod knock - hard to tell without being there. Sound clip/video might be helpful in diagnosing this - but if you can hear it from inside the cabin - usually not a good sign.

But more than likely, it could something other than rod knock - oil pump, power-steering pump, or water pump could be faulty. Any one of the accessories being driven from the crank could be responsible. Might consider pulling the serpentine belt off and seeing if the noise changes at all. Belt tensioner can make a lot of metallic rattling noises at idle that diminish when you load the engine. Can't fully rule out rod knock - as the engine sounds like it seen better days. These engines don't take kindly to overheating events very well - if they show a blown head gasket due to a cooling malfunction - more often than not these blocks, and definitely the heads, are scrapped.

It is unlikely that a bad catalytic converter damaged the engine - unless it was completely clogged, but you would have other issues at that point. Assuming you are getting the P0420 Catalytic below efficiency code? That is pretty common - can be caused by a number of things - usually related to the downstream (post-cat O2 sensor), exhaust leaks, and/or coolant temperature sending unit. Since you mentioned that the water jacket in the engine was heavily scaled - I'm leaning towards faulty water pump and dead coolant temperature sending unit being the primary culprits of the noise and CEL. Also note that this engine (1ZZ-FE) has a reputation of being pretty picky about aftermarket parts, especially electrical and emissions. For the O2 sensor - I'd highly recommend staying with the Denso branded sensor - lots of owners have run into issues running a non-Denso O2 sensor, all for different reasons. Cost-wise, it is pretty much a wash between them - myself, I tested this on my 2003 Matrix XRS - definitely hated the universal Bosch aftermarket O2 sensor I put in to test out - poor fuel economy, spurious CELs, hard to start, down on power. Replaced it with an OEM Denso - night and day difference - ran like the day I first bought it.

Timing could be an issue - VVT-i malfunctions happen from time to time. Might not be a bad idea to verify engine timing. Did you have to replace the timing chain tensioner - do anything to the sprockets on the VVT-i actuator when you replaced the head?

Also note that sometimes, that P0420 code will not go away - as to do with the threshold set point in the ECM. Since the ECM is not user-flashable - one option is to do the sparkplug defouler trick with the downstream O2 sensor. Just do a search on this forum or on any search engine - you'll see tons of guides on what is involved as it affects a number of cars and manufacturers.


It is a BRAND NEW short block, never overheated, but we reused the head after having it resurfaced. I will try to attach an audio capture. The belt off idea is cool, hopefully it goes away, but the sound seems to be more towards the transmission end, though it is very hard to localize. The belt off mode will likely isolate all but the oil pump though. If the oil pump were ticking what is the prognosis, change it quick or will it go along like this?

We do know that the belt tensioner is weak because we get belt vibration at some RPM's, very annoying. 2 NEW O2 sensors very recently and a cat on the way. After the junk that was happening before the short block replacement, the cat is open, but the beads are definitely fould with carbon and water scale and anti-freeze scale!

I'll update after running no belt, hopefully good news that we isolated the sound.

Worried and wondering if it is a rod knock if there is any option to repair without pulling the whole block :-(

Got it - new short block - that is excellent. Do you know off-hand how much the head was warped, if any - as measured with a flatedge - or if you how much material was skimmed off?

If it is rod knock - amount of work trying to separate the upper and lower halves of the block. trying to keep the engine in the car, is a matter of diminishing returns. Might as well pull the whole engine to get a good look at it, make it easier to work on.

As for the oil pump - not very common to have these go bad, but when they do, they fail spectacularly. There has been a number of 2ZZ-GE oil pumps grenading in operation - usually perpetuated by an over rev. Not a fault per say, but doesn't have much of any fault tolerance.

Sounds like that catalytic converter needs to go - sounds like it had a tough life.

It is pretty hard to localize sound on the engine - something from the transaxle side could easily be coming from a bad belt tensioner. Loose exhaust pipe can vibrate the chassis enough to sound like rod knock. The front pipe is known on the 8th gen to eat up the two exhaust gaskets there. Unless you installed new exhaust gaskets - would have missed those. The conical gasket between the exhaust manifold and front pipe - spring bolts there, is known to blow out pretty easily. The rear gasket - between the front pipe and catalytic converter - has two overlapping pipes, can make a tremendous amount of noise and vibration.


aha, the fact that it developed after the fact makes me think an exhaust gasket could make sense. So does Rod knock as I am a believer in Murphy's Law and the worst thing that can go wrong might be what we see. The fact that is sounds bad at idle, rev it up and it goes away almost all the way (if not all the way) makes me think it is not rod knock. I would think it would get worse revving or under load. The exhaust gasket situation is plausible to me because torquing the engine could close up a gap and stop a mechanical oscillation as well as increasing the idle off a resonance.

It does sound like a rattle of something loose.

Would a rod knock come and go at different RPMs or just get faster and slower based on revs?

Correct - rod knock gets worse (louder) as you increase RPMs - will follow the revs, speeding up and slowing down as the revs change. The noise is pretty consistent - should very wildly in intensity from just blipping the throttle. The possible bad exhaust gasket - as the idles increase, the load on the engine as well as the resonant frequency on the exhaust piping can cause the noise to diminish quite a bit. Bad gasket can sound pretty bad - mine was so bad, my son was embarrassed every time I dropped him off at school - hated the car (jokes on him though - he's going to get this car when he starts to drive). Was a deep metallic rattle - some of neighbors called it a death rattle. New $3 gasket and new hardware to tighten it up - good as new.


Sound clip coming. The exhaust sounds possible, because reverse sounds quiet but forward and neutral are loud. Engine mount flex might allow it to seal up with torque on the engine in reverse.

It has thrown P1346 which talks about timing chain skip and it sounds like it could be that too. We used the old timing chain. It was in but at the edge of tolerance.

We now have a new cat conv, I have a used but tested knock sensor coming and we are fixing a few stripped coil hold down bolts with helicoils.

Exhaust gasket, timing chain and tensioner are suspect, as is the computer next. The exhast gasket from the recording would be an excellent catch, last work was the oxy sensors.

I need to post the video with audio to youtube and link it i guess.


is a video of what the car sounds like underneath. As you can tell the sound gets louder at certain times..


CAUTION: The sound of the video is loud. (sorry)



New timing chain, guides and tensioner. New oil pump, cleaned timing advance and screen. We are trying and hoping this is not rod knock, but the last thing we can try now are the exhaust fittings and the knock sensor. Still knocking with a quick trial.

Is there no way to diagnose rod knock? Can we pull the oil pan and seek play in the rods from beneath?

How long can this run with rod knock? Given about 1500 miles and a few thousand in it, it seems horrible to lose. Rebuilder warranty was 1 year and is long past, so no hope there.

IF we were to pull the motor and try to check it and then repair it, is it likely a loser and new short block? We have not driven it much with the knock. maybe 200 miles or less. We're waiting to run it longer after the sealant hardens.




So still knocking after all this. Have a new Cat Converter as the old engine was blowing oil and all. Also have new knock sensor to try. Will check gas evap system and vvti reset. I think from all we are reading this is not a bad engine rod or bearing, YET!


Weird. The noise frequency is not proportional to engine rpm. It is driven to spin/tick under certain loads/rpm's, then slows and subsides. It does sound like it's outside of the engine... Hold the end of a 3 or 4 foot hose on your ear like a stethoscope while pointing or touching the other end to your serpentine belt tensioner* and pulley, AC pump and clutch*, power steering pump, water pump, alternator, head, crankcase, etc, or any suspected component to locate the problem.


OK, updates #12 (???)

We just replaced knock sensor with a used tested unit. When cold sounded the same. Warmed it up, at idle it now sounds good. when we accelerate and let off the gas it gets a nasty rattle going that sounds like piston slap, but I still think this is realted to timing. When we put the new timing chain and sprockets on we did not reset the timing advance unit. We did check and clean the oil control valve, it was clean and fine. This car did run good for the first 1500 miles on the new hort block that has less than 2000 miles on it. It is getting bad mileage, has decent power and only seems to have trhe annoying knock. We have not yet swapped the catalytic converter, but my son says the 2nd O2 sensor is not in the loop on the engine, just a Cat efficiency measure.

So, here are asome questions, fishexpo101 seems to be our best source of good data, though we welcome suggestions from others.

1. Does cat converter and 2nd O2 sensor act in closed loop fashion with engine operation?

2. What technique would identify a broken or locked VVTI Advance actuator unit? Can you explain better the "locked" state and is there any way to use a timing light or other test tools to validate its state?

3. Can we remove the timing advance unit with the valve cover off without taking off the whole timing cover to reset, check and or replace that one part?

4. What breaks on the Advance actuator and can it be rebuilt?

5. Should we avoid opening the unit up once removed or should we open it up?

6. Is it spring loaded and hard to reassemble?

7. Can it be soaked in Seafoam or cleaner and then tested with air or oil under pressure?

HELP, we are running out of ideas and we really don't think an engine that can often sound so good, but sometimes have some noise is really bad after 1500 miles or so.

Just too unimaginable!

People seem to suggest synthetic oil and higer octane gas. Are those good ideas? What about a gas additive for octane boosting to help troubleshoot this?


Have you seen my post #12 at all? We finally got to actually hear it on video, to provide an accurate impression. I'm the only one to have responded to it so far.


We bought an automotive stethoscope and tried it from above and below and cannot isolate the sound. I am thinking it is a timing inconsistency, but there is no clear spot that makes it practical to tell what is happening. Good thinking though.


Timing gear problems I've heard typically makes it sound like a little diesel engine, especially at idle, and before a catastrophic failure... You can't even isolate the source of the noise at all??!


Have you tried running it without the serpentine belt on for just long enough to see if it changes anything?

Just had a chance to listen to the video. Definitely not rod knock - as mentioned by dom, that follows engine RPMs and sound is pretty consistent, doesn't fade in and out like what is in the video. Sounds like a couple of things are going on in the video - the prominent rattling noise from "something" and the constant valvetrain ticking noise, which is pretty common on the 1ZZ-FE engine.

Sounds a lot more like timing chain guide noise or chain slap to me. Could be caused by the timing chain being too tight/too loose, could be a mis-alighnment with the sprockets, VVTi actuator not "locked" before reinstallation, and/or timing is off (jumped a tooth). These all could explain poor fuel economy, but the car still drives. Still could be something related to mechanical contact with the exhaust system and/or engine itself. Could be as simple as a excessively loose exhaust heat shield or a loose or misalighned engine/transaxle mount.

Seafoam is pretty mild of a cleaner - probably won't do much for you, deposit cleaning wise. Could try disconnecting the electrical connection to the OCV, see if that does anything different. As for the actuator itself - a number of people have pulled them apart - usually to dig sludge and heave oil deposits out of them. Definitely need to get your hands on the factory service manual or similar - as there are a number of diagnostic tests to see if the actuator is functioning properly. Possible that it was locked correctly, but there was excessive wear on the end plate that caused it to get goofy timing. This happened on a number of earlier 1ZZ-FE engines, especially the ones in the 7th gen Celicas - as those owners tended to push their cars a little harder than the Corolla owners.

Doesn't sound like piston slap to me - no predetonation - so higher octane gasoline will not help. If the actuator is faulty, probably easier to just source a new or used one - as rebuilding it may not "fix" the original condition that caused it to fail. Should be too hard to reassemble - there was a couple of guys on TN that did just that. You actually perform the test with an air compressor and some tape to cover up the oil holes. There might be a trouble-shooting guide floating around the net, as you are not the first to run into this issue.

You've eliminated a lot of possible culprits by installing the replacement short block - then methodically swapping in parts. I think if you concentrate on the timing components - you might finally get this issue licked.