Base idle speed setting per the Rave for a 96 disco v8...



yet my intake has no bypass valve hose that I can see.


What am I missing?
How can I confirm base idle setting (which i want to confirm was not tampered by the previous owner) without blocking off this bypass hose?

 

Those instructions are likely for a 3.9.

 

aha you are right. I didn't notice that.

I will look at the Rave again but i am almost certain I am looking at the 96 specific manual...

 

If you are missing the version of RAVE you need, check the link in my sig.

 

I looked, and you only seem to have the same ones I have.
the D1 workshop manual and the 95-96 workshop manual you have are both the same, and only indicate procedures for the 3.9

 

I believe on the 'coil pack' Discos the ECU achieves a pre-determined base idle by manipulating the IACV and taking a reading from the crank pos sensor. In as much, the 'base'' can only be adjusted by 'Testbook'. At least that is the intention to the best of my (somewhat limited) knowledge.

The fuel injection manual has this to say about it....

 

gc3,
I asked the same question back in Oct.2018
https://landroverforums.com/forum/di...m-91503/page2/
You need a scantool. Makes we wish I still had the HawkEye scanner!

 

I was going to start a new thread and ask if anyone has reset the base idle on a 4.0 v8 but I see one was already going.

I just reset my adaptives on my 96 Disco 1 using robertf's GEMS app and there are times when the idle it too low in park that the engine stalls. I figured that I needed to reset my base idle and looked at my Workshop manual and noticed the information given was for the 3.9 v8 as mentioned.

Still- I would think the procedure would be the same but just plugging up the vacuum lines in their different location on the 4.0v8 vs 3.9v8 engine and adjusting the idle set screw.

Am I missing something?

Thanks

Brian

 

No as the 3.9 & 4.0 both use the same specs in setting up the base idle adjustment before allowing the ECU to maintain constant idle by the IAC valve. I bet ya a Bier the IAC is sticking as well you checked for old cracked vacuum hoses to the plemum top and IAC valve possibly bypassing uncontrolled air, aka vacuum leak?
Before you touch anything you NEED to check and adjust the throttle butterfly's stop first. By now it might (most the time) have shifted due to wear of the butterfly stop screw hitting against the butterfly stop lever indenting it over time causing the butterfly to rest at a slightly opened position, "over center" of the 90 degree position (perpendictular to the bore's air flow). This will mean when throttle is slightly applied the butterfly will close down air flow before hitting the 90 degree position then opening up again like under normal throttle opening.
On a bad note memory serving me 10 years ago that butterfly stop adjusing screw is on the bottom of the plenum top. You'll have to remove the plenum top for access it. The butterfly as well the air intake clean and clear of carbon and varnish buildup? Only then if required, very rarely moving onto the next step of readjusting the base idle rpm's with the IAC bypass hose plugged off. A 99% chance your problem is NOT the set idle rpm issue out of spec. Air passing by the butterfly at idle must be within the closed and open operating range the IAC valve can handle or else the IAC becomes usless. A machinist depth gauge works best, a dial or vernier caliper second choice of tools. Measure at the top and bottom of the air inlet bore against the bore ID walls,12 and 6 position to the inlet edge of the plenum intake. The depths should be equal hence the butterfly is stopped at 90 degrees to the air flow before attacking the base idle adjustment. Before any of this I would clean and lube the IAC valve first. Lube NOT BY OIL unless you want it to get gummed up again. Clean the bypass port under the IAC also making sure the valve seat area is clean.
Carefully clean the tapered head of the IAC as well the shaft going into the motor. Strong carb cleaner can and will destroy the varnish windings of the stepper motor so only a damp rag strip cleaning the shaft. What I found works best for me the past 20 years is once cleaned and dry to add a little Lock-Ease liquid based graphite as used on locks. Plug in the IAC valve without installing it to the plenum, in hand hold it and have a helper turn on and off the ignition a couple times NOT STARTING the engine. You will see the plunger extend and retract smoothly into the IAC body. Let the solvents evaporate leaving a dry graphite film coating on the shaft not collecting sludge or getting gummed up again for a long while (hopefully) sticking again. Install the IAC and plug in the connector. Sorry for the long novel......~~=o&o>......