4agte wont idle when cold

[Murvz]

My 4agte does not want to idle when first started.. it starts fine and once warm, idles and drives like a dream. Wanted to know if anyone else had experienced this problem and/or could suggest somewhere to start troubleshooting.

Cheers!

[trdee]

sounds like you don't have cold start idle-up....16v or 20v? if 16v have you connected the coolant lines up to the throttle body? if 20v have you wired the ISCV in to your ecu?

[Murvz]

It's a 16v.. and I don't think I do have the coolant lines hooked up to the throttle body. I'm pretty sure I used the coolant outlets from the block to cool the turbo.. where are the ports located on the throttle body and how does this affect the cold idle?

[Cuzzo]

How's your tune and what computer?
I'm guessing microtech?

[Murvz]

Yeah I'm running an older microtech lt-8.. had a dyno tune last year and it didn't change anything.. The tuner couldn't work it out. I think trdee is Def onto something. I took a look at the throttle body last night and I can see one of the coolant ports at the front that isn't connected up.. but I can't see where the coolant would exit. Once I locate it ill just put a t piece in the coolant lines running to my turbo and plumb it up.
Has anyone got a link to a tech drawing that shows the location if the ports?

[trdee]

there are two ports, side by side, on the bottom of the throttle body. you cant miss em

tee them into your heater lines and then raise the idle! the coolant will heat up the wax pellet and lower the idle back down when the car warms up. voila! cold start idle sorted.

also running on a microtech you will probably struggle with cold start either way. iirc they have no cold start fuel enrichment tables do they?

[Murvz]

Cheers trdee! I'll give it a go.. it has to make some sort of improvement considering that I had no coolant running through there in the first place! I'm quiet new to the car building scene as you may have gathered. This datsun is my first so I'm learning as I'm going. As far as computer mapping goes, to date I have left purely up to the professionals but I have been told that microtechs are renowned for a rough idle.. I'll hopefully get a chance to plumb the throttle body this week and I'll let you know how It went

[trdee]

whereabouts do you live? i could swing by and give you a hand with some things if you like. although not this weekend... toyotafest

[SHEPPO3930]

is this a drag car, race car, or daily driver you want to be perfect?

if you can't get the throttle body to work as posted above, you may have to look at the tune. you could play around with the timing in the temp compensation table of the ignition table, might be able to speed up the motor using timing advance when the motor is cooler. another option would be to add a cell in the timing map just below the idle speed (say 200-300rpm below) and then advance the timing in these cells a little. if the revs drop down into the lower rpm cell the timing will be advanced and speed the motor back up. might end up with a wondering idle but it might stop the motor stalling.

as a last ditch effort you could get an older style open/closed idle control valve, bypass the throttle body with it, and run it off a temp switch or aux output on the ECU. it's a crude way to speed up the idle when cold (valve open with 12v from switch/ecu), and it will close the valve when the motor is warm enough to idle without it. cheap, easy to set up with a separate switch and some wires/hoses.

good luck with it... try the OEM throttle body first tho!

[Murvz]

On inspection of the throttle body it appears I'm missing the auxiliary air valve (as my 16v publication calls it ) is missing all together. I didn't realize it was missing when I bought the engine. Makes me wonder though why it was removed. I live in newcastle trdee but I'm going away for a month at the end of the week so wont be able to have a good crack till I get back. Sheppo, I'm just building a weekend driver. The shit cold idle was just annoying me. I think I'll try and obtain an auxiliary air valve and go from there.. cheers for the feedback lads. Learning a lot!

[old_mr2]

I have heaps of throttle body spares that might work for you and I am in Newcastle. Let me know if keen.

[Murvz]

Keen as a bean my friend. . Pm sent ��

[ToyTA22]

Murvz. Make sure none of the throttle body holes have been plugged with silicone or other product.