Re: [doc] Spare Idle ECU

[Nick Tomlinson <nickandkathryntomlinson@xxxxxxxxxxx>]

Hi Daniel,
 
I'm a control system programming engineer (for my sins) and the number of times the Programmable Logic Controller [PLC] (black box!) is blamed for production/ process faults is unbelievable. Most of the times they are not the fault but wires and/ or instrumentation (sensors). Same applies for cars. As long as the basics have been checked first.
 
Checking the idle speed motor valve...
 
Remove valve. Spray carb cleaner in it, shake it, spray wd40 in it. shake it. Pour out excessive wd40.
 
On a test bench, use a multimeter and then measure the resistance from the middle pin to one of the outer pins. Should be in range 5-20 ohms of 150-250 ohms (depending on model). Now repeat for middle pin and other outer pin. Should be near same result as for first.
 
Now, carefully touch from a car battery 12v to the centre pin then MOMENTARILY connect the 0v (earth) connection to one of the outer pins. This should either fully open or fully close the valve. It will shake as you do it. Test by blowing through the valve with your mouth in the direction on the arrow stamped on the side of the valve. Do the same test and the valve should go in the opposite direction.
 
If the valve doesn't move then it is probably seized. If it is then chuck it in the bin and buy a new one. I'm sure Martin has some and I'm presuming you live near him (down saaaaaarrff guv'nor). I live up north about an hours drive from ChrisP's
 
Also, with the ignition on position 2 and the idle speed ecu connected you should get 12v on the centre plug. If you don't check the fuse #1 (if my memory serves me right) and the voltage to the ecu (see workshop manual). If you DO get 12v to the ecu but not 12v at the plug then it is either the wiring OR a diode has gone open circuit on the ECU. If this is the case then a diode can be connected externally as a temporary test.
 
Good luck.
 
Nick.

Daniel Shane <daniel.shane@xxxxxxxxxxxxxx> wrote:
Hi Nick,

Martin did check for correct vacuum routing, leaks, the throttle switch,
thermister at the ECU plug and all OK. He unplugged the Idle-speed motor
and no difference.

That¹s why I asked if anybody had a spare ECU or if I could test mine in
another car.

Now I¹ve got no knowledge for the PRV engine so any and all tips are
welcome. I¹ve fitted new plugs, I'm going to order a new Dizzy cap and arm
as well as new leads.

I¹ll check the Idle motor is not stuck and clean it with carb cleaner.

Is there anything better and the Delorean Manual you could recommend for the
Engine. I¹ve heard of a Green Volvo guide that might be good.

Dan Shane
DOC 423
VIN 4754


On 13/9/04 8:33 pm, "Nick Tomlinson" 
wrote:

> Hi Dan.
> 
> Check basics first before condemning 'black boxes'.
> Air leaks on o-rings/ inlet manifold, dropped off vacuum hoses, vacuum hoses
> connected to wrong devices, throttle-switch, fuses in fusebox, wiring to ecu
> (including the voltage feedback diode to throttle switch), sensor value of
> thermister (at ecu plug), plugs plugged in, idle-speed motor not stuck open,
> the air con mode switch is OFF (another vacuum leak possibility) etc. etc.
> 
> A 'very' Rough guide, with ignition in position 2 you should be able to hear
> the idle speed control valve 'humm' at a certain pitch, with the throttle open
> (opening the throttle switch) the 'humm' should be slightly different.
> 
> Measure twice, fix once!
> 
> Good luck.
> 
> NickT.
> 
> Daniel Shane wrote:
> Does anybody have a spare Idle ECU I could borrow to test that mine is
> indeed faulty. My car now idles at 3500 RPM and can be a pig to start.
> 
> I'm in Lenham in Kent I don't mind coming to collect it or if anybody
> fancies a nice county drive I'll buy you a pint in my local.
> 
> Or is there a way bypass the ECU. I've tried unplugging the ECU and
> starting the car and it does the same, shooting upto 3500 RPM.
> 
> Dan Shane
> DOC 423
> VIN 4754
> 
> 
> 
> 
> 
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