1jz-gte random misfire when cold only.

[Z2TT]

Hi Guys,

My 1jz-gte is running perfect apart from a little Issue that isn't much of a problem as it only does it sometimes when cold, ussuallly after a drive up a few streets then come to lights and am waiting,
it would idle smooth as silk then out of nowhere a misfire, then another one, then idle great. When it warms up it never does it ever.

Tried Different ECU that was good.
Replaced Coilpacks
New Spark Plugs and tried different types and gaps
Coil Pack Connectors.
Igniter.
Tested Throttle position sensor resistances to spec
New Oxygen Sensor
New Map Sensor

The motor is Mint and runs great and has so much power, no hesitation when driving or anything like that,
It's like it comes on when it wants, but only when slightly warm, does not do it right from a cold start in the driveway,
does it when it's warmed up a little bit but not fully warm.

Could it perhaps be a crank angle sensor, I have an oscilloscope, would it show some weird readings during the misfire if it's a Crank sensor problem?

[George]

If you insist on dodgy CAS try first to clean it thoroughly from metal particles that its magnet can, in theory, attract from somewhere

Best of all find someone with a scanner and see what happens upon your misfires. If you're lucky you will see some sensor's signal changes instantly and then settles back, for example this can be the case with coolant temp sensor.

I've personally seen live data from 1jz-ge's off jzs171 and jzx100 and if you got a laptop you can arrange your own scanner for under $50. Don't know though if earlier models support scanners.

Another possible option to find a faulty sensor is to disconnect sensors 1 by 1 forcing ECU into failsafe mode and see if problem disappears. Virtually every sensor can be disconnected this way while engine would still keep running.

[Z2TT]

Motor is off a JZZ30, Could I buy a Scanner for this?

[George]

Buy? Probably yes, but better diy
use software from the bottom of the page below
http://primavistalab.com/myengine/
and here's your interface cable
http://a.d-cd.net/90c7d8u/960.jpg

this one will work for most of toyotas produced before 1996, and some very limited list of 1996-2000 models

[bk_]

I've built my own hardware-based "scanner" (OBD reader) many years ago.

You're not going to get much out of it since the data update interval is only ~1.25 seconds.

Best to get error codes out of the ECU.

Does the problem happen after a battery reconnect?

Only on idle?

Manual? Auto?

[beatle]

water temp sensor in the upper coolant hose hard pipe

[bk_]

ECT sensor could be open-circuit / shorted as hinted by beatle.

However, that is only a possibility if you have severe cold start issues.

[beatle]

Mine started as a miss during warm up before going shitty cold start.
Only about $20-30 for a tridon one, considering how much youve spent so far its cheap.
Also clean/ test the idle speed control valve

[beatle]

It sounds like its not quite transitioning from cold start mode right.