2JZGE Idle Misfire and Noise Help

[TRD-1]

Hi Guys,

 

Ive recently brought a Mk1 GS300 and I noticed a idle misfire along with a creaking type noise coming from the cam belt area only on idle, it happens below 800rpm above that its totally silent, I can't work out what its linked to sometimes its always there below 800rpm sometimes the car will idle at 700-750rpm and be ok so its a bit intermittent aswell.

 

To try and eliminate the issue Ive replaced a few service items (cap, rotor, plugs, oxygen sensors) with new parts and also tested the following with replacements from a fulling working 2JZGE: leads, distributor and coil however I can't seem to find the cause. Ive re-set the timing a few times and only on idle it seems to do this, so Ive set the timing just slightly out and it will idle between 900 and 800rpm and it won't misfire and drive absolutely fine.

 

Ive re-set the tps, tried a different sensor, done resistance tests on the idle control valve, MAF and TPS and nothing is out of spec, Ive also cleaned out the throttle body, EGR valve and still can't find the cause.

 

Any help or suggestions would be highly appreciated!, Ive linked in the video to the noise and misfire.

 

[Mike2JZ]

Remove the aux belt and see if problem/sound persists. If it does, then

 

I'd get the rocker covers off and check your valve clearances as specified in factory manual. Also take a look at the conditions of the cam lobes, check for scouring etc. Check the torque on your cam pulley bolts.

 

If the head looks clean then I can only think that the noise would come from something from the cambelt system like a tensioner bearing, but that wouldn't explain the misfire.

[TRD-1]

Thanks for the advice, I shall further investigate and see whats happening inside the cam covers!