torrbi

Hi. I have this intermittent sound that seem to be happening for some but with no clear solution. With all these threads about knocking where it’s more obvious a TCT problem or rod knocking, I am creating this thread for this type of knock only.



This tapping sound is only audible in idle around 700rpm, and seem to be most evident when the engine is hot (most likely because of lower rpm at idle when it’s hot). The sound seem to follow half the engine rpm, which makes me lean towards valvetrain or piston pin since ignition is done every second engine revolution.



Thinks I have done/tested:

- adjusted the valves to spec.

- carefully sanded the worn surface on the worm gear in TCT.

- Ran the engine without serpentine belt and replaced the idler pulley.

- swapped around the ignition coils and spark plugs.

- located the knock from cyl2 by pulling the injector power on one each cylinder. It seem to stop with no power on cyl2. Its hard to determine the knock with stethoscope. Sounds more on the exhaust side of the engine.

- replaced rod bearing on cyl2.

- replaced the exhaust gasket.

- new 5w40 engine oil plus oil filter.

- compression test with even result on all cylinders.

- new spoon motor mounts



Worth to be said is also that this 2001-F20C2 is new for me but has gone 55k miles and replaced my old 120k engine which grenaded during a track event. When I got the engine I noticed 7 of 8 intake retainers to be cracked, which I replaced with Ap2 retainers. Knocking sound was the same before I swapped retainers.



Any ideas?


The sound is louder IRL compared to the video and sounds the most behind the right front wheel when the hood is closed.

noodels

tried putting your foot on the clutch ?

torrbi

Yeah that too. I’m very confident it’s from the motor itself since I got a change in sound when I pulled the second injector cable

noodels

Have you done a compression test ? just to get that out of the way..soo
am thinking little piston slap <oval bore> or valve train like you said.

Slowcrash_101

How are your motor mounts?

torrbi

forgot to add that! I have even pressure on all cylinders, around 150 - 155psi. I have thought about piston slap aswell, but I dont know how that sounds.

forgot to add that too. They are brand new from Spoon.

Slowcrash_101

Lost motion assemblies are in place?

Either that or bad injector.

ss2ooo

FYI - Sounds exactly like my engine! From memory, it happens when hot only

windhund116

I'm guessing this is a good thing?

torrbi

Im actually about to take apart the assembly to have a look (again). Someone said to me that he had a cracked roller that the lobes pushes on. It apparently made this noise.

The injectors are old (110k miles/180k kms) and could be a problem. Now when you say it I actaully think I havent swapped the injectors from cylinder to cylinder. Since the motor is half way out of the car I think I will start with sending them to a shop for testing and cleaning.

Hmm for how long has it sounded like that? Does it disappear when you apply some throttle? Did something happen to the motor like an overrev? Im just curious since I know for a fact that mine has by its former owner.