Problems with 20 valve 4age

[gerardw]

G'day guys" I'm looking for a bit of advice, I got a silver top 20 valve with some running issues.
First off this conversion was done some time ago (15000 klms) and up to now has had no issues, so it is all wired correctly. Currently it's chugging black smoke ( over fuelling) and generally lacking in power. The idle control valve is clicking rapidly and continuously yet it idles ok. When I turn on the ignition the engine check light comes on as usual, then when I hit the starter button the light goes out while its cranking, it takes about 10 seconds of cranking then the check engine light will come back on and the engine starts soon after. The ecu is not showing any error codes. Thanks in advance for any help.

[dumbass]

is ther battery power hooked to to ecu
otheriwse it wont save any codes
maybe disconnect some sensors to make ecu see a code
then see if it saves it

also look inside ecu
they are very prone to fking to capacitors

[gerardw]

well dumbass, you may well be right. heres a couple of pics of the ecu. it definately wasnt this way when i installed it.burnt tracks in circuit board.jpgleaking capacitor.jpg
as you can see there is some burnt tracks on the printed circuit board and also leaking capacitors........seems like a good excuse to go aftermarket.
one of those tracks leads to the g2 pin which if i remember correctly is for the crank angle sensor.

[gerardw]

I decided to have a go at fixing the ecu. I replaced all of the capacitors and fixed the circuit board, this has made little to no difference to the running issues. It does seem to idle a little smoother but still won't rev clean and is blowing black smoke. I'm starting to run out of ideas. Should these motors run ok with the iscv completely removed? I'd like to see if the iscv is what is causing the problems.

[dumbass]

20 v ecus always fail
So these days I rewire them to suit a blacktop ecu
Or just go aftermarket

[jondee86]

Should these motors run ok with the iscv completely removed?

All the idle air for a factory 20V 4AGE goes thru the ISCV. The ISCV is a 3-wire rotary solenoid, and does not "click". It is controlled by a PWM signal from the the ECU, which modulates the valve position to maintain a constant target idle speed. The valve is only active when the TPS IDL switch is closed.

If you want, you could remove the ISCV and put a fixed orifice in the hose or port that leads to the common vacuum rail behind the ITB's. Just plug it up with something that you can drill a hole in for idle air. Totally blocked off, the engine should stall. Start with a small hole, and enlarge it until the engine starts reliably. Because the ECU now has no way of contolling the idle speed, your idle speed will be low on a cold start, and rise as the engine warms up. You need to find a happy compromise.

Or you can unplug and block off the ISCV and crack the throttles open on the main throttle stop. You should reset the TPS so that the IDL switch changes state when the throttle is on the stop. That way the ECU will still make the changes to fuel and timing that help with a stable idle. Idle speed will rise as the engine warms up.

Cheers... jondee86

[gerardw]

Thanks for the reply jondee and dumbass , I'm going to try removing the iscv today as it is clicking, seems like the solenoid is going from full open to full closed and open close open close etc. that's what the clicking noise is and you can feel it when you put your hand on the valve. What I'm trying to determine now is whether its a faulty valve or a faulty ecu controlling the valve.
I figure if I can make the engine run well without the valve then I need a new valve if not new ecu?????

[gerardw]

Ok, I disconnected the iscv and blocked the vac lines. I then tweaked the throttle cable to open the butterfly's enough for it to idle. No change to the poor running. So I guess I'm up for an ecu after all?????? I sent an enquiry to adaptronic last week but got no reply, I guess I'll send them another.
I'd really like to try another factory ecu though to make sure that's the problem. It'd be a bugger trying to tune an aftermarket ecu if there are problems elsewhere.

[jondee86]

I'd really like to try another factory ecu though to make sure that's the problem.

^^^^ this. When random weird sh*t starts happening on a 20V, it very often comes down to an ECU problem. FWIW I have an Adaptronic e420c ECU on my 16V with ITB's, and it controls the ISCV no worries

Cheers... jondee86