96 1uz cold idle pulsing and nearly stalling (vids attached)

[Crigsta]

G'Day Guys, been chasing an intermitent cold idle issue for the last 6 months.

most of the time when i start the ute cold, the 1uz's idle hunts up and down from around 1200rpm to 300rpm (nearly stalling each time). you can get it to stabilize if you give a light touch of the accellerator and ease it back down to idle slowly but as soon as you rev it again, it starts pulsing up and down. Once it warms up for a few minutes it idles at the normal cold 1000-1200rpm and idle is fine even when revved agressivley.

things i have replaced:

New plugs
new ECU temp sensor
second hand rebuildable IACV (functions fine).

Any suggestions guys?


VIDEO: stone cold startup: http://youtu.be/t5VokKdlDTY


2ND VIDEO: after 5mins of running: http://youtu.be/Jrw0G85sXpg

 

[gloverman]

Can you try this simple test and report back. Unplug the IAC , check for power at the centre two pins. With the test light still attached , start the engine , you may need to hold the idle up. run the engine for 20seconds and then turn it off. Tell me when the power turns off.

Also check the TPS settings. TPS is a large consideration for idle.

 

[Crigsta]

Thanks gloverman. Will check how long power stays on after shut down.

I have previously adjusted the tps when I adjusted the base idle (setscrew on butterfly). Cause it was only idling round 500rpm when warm. I adjusted it as per the manual with feeler gauges between the stop etc to get the idle value correct. I might give it another go and see if I arrive at the same setting.

When the motor was first run, the cold idle worked perfactly for the first few days, then it hasn't been the same since. Since then I have been replacing things etc to try and fix.

 

[Crigsta]

What I don't understand is that if it starts up stone cold. And won't high idle, why doesn't the ECU open the IACV up more to compensate? It doesn't seem to function correctly until there is a little heat in the motor. If I stabilize the revs when it's stone cold and fluctuating, it idles around 750rpm (normal warm idle) but after a few minutes the revs kick up to a normal cold 1000-1200rpm.

 

[gloverman]

Ive seen this alot. Who wired the engine??

 

[Crigsta]

I wired it up myself using the 1uz wiring diagrams. Everything from motor to ECU was left connected. I got original ecu with motor.

Here is a wiring diagram that I drew for the external connections to ECU.

 

[gloverman]

Check that power feed to the IAC and we will work from there. Do you have a UCF20 or a UZS151 engine?

 

[cruising]

Maybe u have hole leak in air manifold

 

[Crigsta]

Engine is supposed to be a UCF21.

Here Is a pic of the ecu I snapped before it went in the car. Thought it might come in handy.



Will check power duration to IACV tonite.

Another thing I have noticed. This cold start idle issue seems to be related to outside air temp. Seems worse on a cold day. I fired up the ute last night and it wasn't as bad. It way maybe a few degrees warmer than same time yesterday.

 

[cruising]

Check wiring maybe u make mistake
Many colours easy mistake

 

[pinkytamz]

hi you have the same ECU as mine and i am also having faults did you get yours sorted would love to know

 

[Crigsta]

No. I didn't end up sorting the issue.

Bought a stand alone Adaptronic ECU and had it tuned. Drives heaps, heaps better and makes more power too.

Sorted the cold idle issue, the random lean surging (felt like it was running out of fuel) and now I can control thermo's from the ECU plus a whole heap of other cool stuff.

Pulled 150rwkw which isn't really a big number compared to 2wd cars but I am pushing a 4wd driveline and 35" muddies.

 

[Big_Lux]

How did you fix your cold idle issue? Still having trouble with my idling woes..

 

[Crigsta]

There was no longer an issue once I installed and tuned the new ECU. it seems that the idle issue was contained to the standard ECU. Not something you want to hear though.

The Adaptronic has no issue in controlling the same idle control valve that the standard ECU seemed to be having trouble with.

 

[gloverman]

I fixed another vehicle with similar issues today. Poor idle just one of them.