Hmmm - seems I didn't post this to the list, just to Pieter owing
to the way the list mailer is set up, so I thought I'd post it now for
general interest. Hope it's not considered a waste of bandwidth! :>)
Regards,
Franc.
-------- Original Message --------
From: Franc Buxton <fab@dcs.warwick.ac.uk>
Subject: Re: 14 CUX EFI
To: Pieter Erasmus <pietere@adsmr.co.za>
Pieter Erasmus wrote:
>
> Hi all
>
> My name is Pieter Erasmus, and I am from South Africa. I am battling with my
> Range Rover and hope someone here can help me. I have a 1984 Range Rover
> Classic and recently converted it to a 4.6 V8 out of a later HSE, and fitted
> the 14 CUX hotwire fuel injection from a 3.9 V8 Discovery. The main problem
> i have is that when I start the car the revs go very high, to about 2000 rpm
> before settling down in steps. With this in mind I have the following
> questions :
>
> * The ECU apparently needs a road speed input. As my Rangie has a pure
> mechanical drive for the speedo, I cannot supply this input to the ECU. What
> negative influence will the absence of this input have and is there a way to
> overcome this?
> *
> * The ECU needs some wire, in the case of a manual g/b earthed through
> a 520 ohms resistor. When i do this the engine idled to high, so I dont have
> any "earth on this input. Is there any negative effect on the ECU?
> *
> * The ECU chech light (on the instruments) is not connected, will this
> cause the ECU to malfunction?
> *
> * How can I determine whether the ECU is in "limp" mode and if so, how
> can I reset it to get out of "limp" mode?
> *
> Sorry for all the questions but I have turned grey trying to solve this
> problem...
>
Hi, Pieter,
I can answer most of the questions, but whether the answers will help
aty such a distance from you I couldn't say! (I'm in the UK).
Firstly, the 4.6 engine was never fitted as standard with a distributor
as far as I know, so I assume a different front cover has been fitted to
accommodate one, and that all the induction system from the 3.9 is also present.
The ECU incorporates idle speed control, and should indeed 'flare' the
engine on startup and gradually reduce idle, but the base idle needs to be set,
along with the throttle sensor base setting, to make this work properly. Various
internal calibration parameters will be incorrect to work perfectly with the
4.6,
but it should be better than you seem to have presently.
There should be an air hose leading round the back of the plenum chamber
to the idle stepper motor assembly. To adjust base idle, remove this hose and
plug
both ends where it fits. The idle speed should then be about 600RPM; if not,
there
should be an idle adjuster screw on the top near the throttle spindle (it may be
plugged with an anti-tamper plug which you should remove). Adjust this until
idle
is about 600RPM, then replace the hose (after unplugging its end fittings :>) ).
The idle control will not work properly without the road speed
transducer,
as it uses this to determine whether the vehicle is moving (and therefore on
overrun if the throttle pedal is closed) or stationary, upon which it will try
to
control idle speed. Without the sensor, it will try to reduce idle speed when,
for example, you are descending a steep hill on engine braking, resulting in the
engine stalling when you do finally come to rest. A Range Rover of about 1989
vintage
should have a suitable cable and sensor (the sensor is also on later models,
but they
had no cable from it to the speedo, which was electronic). The sensor just
needs an
ignition-switched 12-volt feed to one wire and the appropriate ECU wire on the
other.
The roadspeed input may also cause the ECU to limit your maximum road speed. If
this
becomes a problem, custom ECU chips are available (from me amongst others)
which will
eliminate this action.
The 520-ohm resistor tells the ECU that you have a manual gearbox. If
it were
automatic, the ECU would change idle control parameters depending upon whether
your
autobox was in 'neutral' or 'drive' to compensate for the different loading. No
connection denotes 'drive' which will reduce idle speed but open the stepper for
extra air because of extra load. The resistor would be best, but it should cope
adequately in any steady state in my experience, and parameters will be about
right
with the resistor when you fix the other problems above. Idle target speed is
usually
about 600-700 in 'drive' and 700-800 in 'neutral' or manual. This can also be
changed
with a custom chip.
Connection or not of the check light is only relevant to local
legislation. I
think it's useful sometimes to indicate whether the ECU is happy, so I would
connect it.
It's just a light with 12 volts on one side and the ECU output on the other.
That brings me to your final question - the check light would probably
tell you
whether the ECU was in limp mode, although with UK models, this doesn't always
seem to
happen! It will only adopt limp mode (AFAIK) if the airflow sensor is faulty or
disconnected. What you really need is a local facility with the proper
diagnostic
kit to check it's all set up properly. Sorry, I'm a bit far away :>). Good luck
with all of it!
Regards,
Franc.
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