I'm trying to get my hot idle from 950rpm down to 800rpm (92 hiace 2779cc 3L engine)
Identified cold and hot idle and full rev limiter screws - adjusted the hot idle but no difference (just a 3mm gap between it and the stop)
If I force the cable cam back the hot idle screw seems set right now - though as soon as I let it go it springs back up to 950rpm
The reason for this seems to be underneath the adjustable throttle sensor (currently adjusted exactly mid-way with anti tamper paint on) though I cant see a way of altering without removing the throttle sensor
Thought I'd ask for advice before going further.

What am I going to be adjusting under here and why?

The throttle sensor (I imagine) sends throttle position info to a micro chip - What will the chip do with this info
ie
What will it alter and how?

Anyone know what readings should be got from various wires on the throttle sensor?

I did adjust a primera petrol some time back (getting correct ohms and volt readings at various throttle settings)which resulted in better mpg but had the luxury of a haynes manual for that -
Toyota insist 'they know nothing' of service specs.
Though the idle speed is my primary question - as I'm still not bettering 18mpg maybe there is mileage with the sensor?
Can anyone advise as I dont want to make things worse by meddling with things I'm not sure of!
Chris
- (#8365) chris turner, 8 May 03 10:37

Well... are you sure the cold idle lever is freeing away from the throttle cam? There's a screw and locknut on the lever... If it definitely is free, then throttle sensor
is used to defeat the aircon at high throttle settings (tells the compressor to disconnect). It might also link in to the EGR system. Dunno. Now, if it's the same as the townie, there's a hole in the underside of the sensor that a pin in the throttle cam engages with. But it's also possible to stick it in wrongly. You'd normally feel a grating then, tho.Feel free to slacken the two screws and turn the pot slightly, see if it cures the problem. If you turn on the ign and aircon, you'll hear the clutch click out when you reach the control point.

- (#8366) david miller, 8 May 03 11:26

Cheers David
Yes, it controls the a/c as you describe (just before the throttle is decked)
Note on cd that is linkage is adustable under throttle sensor but is shows the adjustment in degrees (not having a protractor that small I'll leave that as a last option)
However, cold idle lever - is that the thermo device? under the idle up vac device?
Is this a cold start thermo thing similar to ones fitted to some carbs on other brands? (used to be one on my 205 auto and I packed the pushrod bit with coathanger wire as it became less effective)
I note the connection to cold running stop but does this device move all the linkages ie
if the cold run thermo device had been badly adjusted or worn inside would adjusting this bring my stop back for the hot idle stop?
Chris

- (#8367) chris turner, 8 May 03 17:14

Under the idle-up, "thermo wax" as they call it is a wax stat heated by the coolant. check that you're getting coolant flow through it- two small hoses come off the back of it. No coolant flow= no expansion= no slow hot idle. Could also mean the timing being advanced too...

The throttle cam isn't really adjustable as such, there are different versions of it...

- (#8368) david miller, 9 May 03 1:05

The thermo works ok as levers are moved away from the cold stop screw as it heats up
Timing - had never considered as thought they were set for life - however could a previous cambelt change hsve something to do with it?
Is it a quick job to check and adjust?
Am familiar with timing issues/methods for petrol - is deisel any different regarding symptoms etc.? Also can a deisel engine pink as I do get a bit of a 'rinky tinky' engine noise until its fully heated?
Chris
- (#8434) chris turner, 9 May 03 18:12

diesel engines run by pinking! re. timing there's two adjustments, the cambelt- line all the pulleys up with their markers, and the pump position- need a dial gauge and adaptor for that.

But that can't affect your idle not going to the stop. If you're sure that the idle up is all clearing the throttle cam then there are a couple of possible reasons for the failure to go to idle. One is the throttle sensor as previously discussed. The second is the pump's been apart and the cam has been put on the wrong way (a spline out on the shaft)and the screw is out too far to try and compensate.
The last and possibly most plausible reason is this. Someone has fiddled with the max. fuel screw, and you're trying to adjust everything else to compensate. How far out is the idle screw turned? Was the sealing wire in place linking the adjustment screws together when you started? If not, it's my guess that someone has turned the pump up on import. Quite common.
If so, you need to locate the max. fuel screw (screw and locknut at the rear of the pump above the injection pipes, a loose fitting metal collar on the end of the threads) and turn it SLIGHTLY. Wait till the engine is warm, then adjust the screw so that idle is low, like 600, then tighten the locknut. Adjust the idle in the normal way, then check max revs. The engine should govern itself at the redline. If not, turn full throttle stop till it does. Scarey, but safe.


Actually, just had another thought. Is there plenty of free play in the throttle cable? If it's adjusted when the engine's cold there mightn't be enough slack to let the cam return to hot idle. Check this first...

- (#8435) david miller, 10 May 03 1:57

Cheers David
Coming home tonight and guess what - now idling at 800rpm!
Strange beast that I have!
Seems to have found its own way down - dont really understand why as it was about 2-3mm away from hot idle screw stop and much further from the cold stop when I last posted.
I think your last point is good as I have taken slack from the linkages and cable - the engine was warm but not true operating temp ie
maybe 40-50ish deg rather than closer to 90 deg.
However both hot and cold screws were free which makes me think the thermo device may play a part - whatever, I will be 'staring at it' on and off until I work that one out!

The pump has been played with as securing wires are missing - though the throttle pot is paint sealed

Would it be clockwise to reduce flow on fuel screw?
Familiar with symptoms and sounds for too weak or rich on petrol - but what symptoms for deisel?
In view of the regular 18mpg I think it may be worth trying -
Is there any way of knowing when you've got the mix about right on deisel engines without gas meters or monitoring fuel consumption by the tank load?
Would a weaker fuel mix make for a hotter running engine? (as on petrol) and can too weak a mix make for poor mpg etc?
Wondering if the fuel flow has not been increased on import, then are there any benefits to doing it?
Guess what I'm trying to ask is how do I get the mix bang on (ish) and are there mechanical hazards if too lean or rich?
Chris

- (#8436) chris turner, 10 May 03 17:51

Well, diesels don't "do" weak or rich. They are an excess air engine. Power increases as you up the fueling until it runs out of air- black smoke. So a well- tuned diesel should BARELY smoke at full load. Excess fuel and/ or advanced timing will cause overheating.

Check before you fiddle with any pump adjustment s that ther is indeed a bit of play in the throttle cable on hot idle, and that the thermo actuator IS moving as it warms up.

Setting up your beast is a doddle compared with the townie because you've no turbo- fewer adjustments! To decrease fueling, turn the screw anticlockwise looking at the rear of the pump. An eighth of a turn is probably too much, so be gentle. You'll notice both idle and maximum revs decrease and so require readjustment. But fiddle until you find a point where you've no less power than you do now. You'll see less smoke and better consumption if it's all OK

- (#8437) david miller, 11 May 03 2:56