What's your cold start idle speed on your 1JZGTE?

[destrux]

It never really bothered me till someone else pointed it out... but when I cold start my car the thing leaps right up to 2,000rpm and idles there till it warms up to closed loop mode (I know this cause I put a closed loop indicator light in the dash). Then it drops to a 750rpm idle, and idles there on a hot start right away.

Is that about right or is that cold start idle way too high? None of my other cars idle that high when cold. Seems like revving right up to 2K like that before the motor even gets oil pressure would eventually cause problems.

 

[f00g00]

Mine runs at around 500 rpm and it slowly creeps up to 800 when it is warmed up.
Have you cleaned your IACV yet? 2000 is extremly high. Did it ever idle lower and then climb as it warmed up?

 

[MkiiiAllDay]

Mine is intermittent, 2000, 1000, or 1500 when it wants, I think it might be my iacv bit not sure

Insight anyone?

 

[destrux]

It never idled lower and climbed as it warmed. Always starts off high and slowly drops. It's been like that for four years roughly (daily driver except winter).

I never thought about it being an IACV issue since the idle control is always spot on once it's warmed up. When I turn the lights on or anything the idle speed stays right where it should, no drop off, so I figured the IACV was working normally.

I've tested the IAT sensor too, and it reads as it should.

This car was an automatic that's been converted to manual. I wonder if this is a side effect of one of the transmission sensors not being present anymore. My car has a JZZ30 Soarer ECM/TCM combo unit, no separate TCM. I just looped the neutral switch circuit to allow cranking and left all the other trans wiring disconnected.

 

[hvyman]

It's supposed to do that.

Iac is always pulled to max open when car is shit down. Ecu will start closing it once started and then closes it more and more until you reach operating temp.

It give the high idle to speed up warm up times.

 

[f00g00]

2000 is ridiculously high when cold. You should check the wires to the iacv end to end to ensure the wiring is correct. Also you can remove it up to verify it is put together right.

 

[hvyman]

Its not that high actually. most jz will go somewhere around 1700.

And if the iac is functioning correctly besides that then the wiring is fine.

 

[destrux]

I didn't rewire the IACV, but I did extend my harness. I'd think any errors would have thrown a code or caused hot idle issues though.

I do run a SAFC to compensate for 440cc injectors. I wonder if the added timing is causing the cold idle to be a few hundred RPM higher than usual? This is a solid 2K, not 1,700. I can't remember if it did this back when I had the stock injectors... it's been so long.

I also have the throttle coolant bypassed, maybe that's screwing with the system?

 

[f00g00]

I have had 2 different 1JZ's and both would idle lower in open loop. I have recently switched to 2j 550's and it runs in the 13 afr range when warm and open loop brings it back under control when driving. Warm up idle is still low in the 550-600 range when cold though. I have an old mercedes 280SE 4.5 with the old D-Jetronic efi and that does have a fast idle till warmed up.
I am running stock ecu so I don't know if aftermarket warms up different.
Hvyman is probably right though.

 

[hvyman]

If you have more timing then it could add to it. The more timing you have it can contribute to raising idle speed among other things.

 

[MkiiiAllDay]

I know this isn't a great fix but have you tried turning the idle screw up until the rpm meets 900 or so, it fixed it for now and it only cold starts at around 1500 for me

Again this isn't permanent but a temporary fix

 

[hvyman]

The ecu will adjust for idle screw adjustment. also that throws your tps adjustment off as well. But it wouldnt be a bad idea to check tps adjustment

 

[destrux]

I tried turning the idle screw down, but I'll try turning it up and see if it effects the cold idle the opposite way.

I did check the TPS, it's in adjustment. I have another unresolved start-up issue with this car (it cranks like the engine is binding every few turns sometimes) and I went over all the sensors with the meter trying to figure that out. I think I might have an intermittent bad cam sensor but it runs fine after it's started so I haven't spent the $200 on the pair of cam sensors yet.

 

[hvyman]

Have the caps been replaced in the ecu?

 

[destrux]

Yes, ECU was completely rebuilt with new caps a few years ago.

 

[Russdeez_1jz]

My 1j idles super low on cold start, sometimes stalling and requiring me to restart it 2-3 times. Does anyone know how to fix this? I was told to buy a new coolant temp sensor plug. Does that sound correct?

 

[MkiiiAllDay]

Probably not the plug but the actual sensor lol, don't know if you meant that or not, but it might be that