Knock as the engine reaches Operating Temp

[Project-X]

Hello,

Heres my issue, I have mk3 with a stock 1jz with 3" exhaust and aftermarket intercooler setup 2.5 inch piping that is the extent of the engine modifications.

It starts up fine good start up oil pressure around 90psi and no boost leaks but as I reach operating temperature and the the oil has warmed up the engine develops a knocking noise. It is not a constant knock it happens about every 2-3 seconds.

I am having a hard time figuring out if it is a rodknock. I have no engine codes, the engine seems to run fine. If anyone has run into something similar or if you know for a fact that my engine is probably kaput I would appreciate the input.

 

[IJ.]

Does it get worse if you bring the rpm up to around 2400?

 

[Project-X]

No sir, The knock seems to disappear as the revs rise. I tryed to listen for it at 2-2400 rpm

 

[IJ.]

Normally RK will get worse around 2400>2500 then go away, you can try running it till it knocks then pull an injector clip and see if it stops, do one cylinder at a time replacing each clip then move onto the next.

If it's actually RK it should stop totally once the clip is off.

 

[Project-X]

ok thanks I will give it a shot and post
my results

 

[te72]

Just an idea, but I have an exhaust leak somewhere between the head and the exhaust (obviously), and it's had the paranoia in me think it was a rod knocking. Although in my case it happens only when the motor is colder.

Could also be the engine miss firing, perhaps? Mine does that on occasion at idle.

 

[Project-X]

hmm things to consider. I know I have an exhaust leak as well I will have to check into the misfire though

im going to pull each plug and check after I try pulling the injector plugs individually.

thanks for the suggestions

 

[te72]

Wouldn't you have to pull two plugs at once? IIRC, they have shared coils on a bracket... three pairs of two plug boots?

 

[89niner]

Wouldn't you have to pull two plugs at once? IIRC, they have shared coils on a bracket... three pairs of two plug boots?

If there is no connectivity to the plug, the plug will not fire. Therefore one plug wire at a time.

 

[IJ.]

I suggested pulling the injector leads as it will show up the same with no chance of zapping him..

If he pulls an injector lead and the knock stops that's the knocky cylinder, if it doesn't change the RPM or cause a miss it's either a dead injector or a dead coil/plug/lead so you investigate further.

 

[Project-X]

Ok here are my results, I successfully unplugged each injector individually and the knock stayed idle dropped and I got a miss each time. I also tryed unplugging my coils one by one and the same thing the knock stayed. so I decided I would try and pin point the noise with a stethoscope.

I started at the head and worked around could not find much. I jacked the car up and started it up and waited for the knocking sound to start so I could check the bottom end and the sound disappeared with the front end in the air!!

let me know your ideas!

 

[te72]

If there is no connectivity to the plug, the plug will not fire. Therefore one plug wire at a time.

I understand the concept, but on the 1jz, your plug boots are on brackets in pairs. IIRC (it's been a while since I changed plugs), to pull one wire, you have to pull both due to the design on our engines.

I suggested pulling the injector leads as it will show up the same with no chance of zapping him..

Aww, but getting zapped is half the fun man!

I started at the head and worked around could not find much. I jacked the car up and started it up and waited for the knocking sound to start so I could check the bottom end and the sound disappeared with the front end in the air!!

let me know your ideas!

Maybe your car wants to be an airplane? Seriously though, that is kind of odd to me. Perhaps, is there an oil delivery problem, that was alleviated by tilting the car back? What happens if you put the front end back down? What about if you jack up only the rear end, does the knocking get worse?

 

[IJ.]

Try running it with the accessory belts off, try it with the Dipstick out, Auto or manual?

Try running it with the Oil Cap off and see if there is a change in knock volume.

 

[shipkiller]

clutch or something? if with the front end is in the end and the knock disapeird, might be the disc sliding on the input shaft in direction of the rear... I don't know?!

 

[Dylan JZ]

check your crank pulley for play if you haven't yet done so.