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Tom, ASE Certified Technician
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Experience:  ASE Certified Master Technician
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Land Rover Range Rover Classic LWB: Range Rover poor running

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Range Rover poor running stalling when warmed up. 1994

Hello, I'm Chris. Thanks for visiting Just Answer.


If you have no t done so yet I would start with new plugs and wires then use sea foam to clean out the throttle body, intake and combustion chambers to see if this helps. Can you do this or have you already done that.


Customer: replied 4 years ago.

After trying nearly everything we disconnected the vacuum line to the Fuel pressure regulator and "excersized" it with a small hand held vacuum pump. After about 5 cycles or so of pressure and vacuum the idle improved substanially.

We sent for a new regulator, will see Monday?

Good job
Customer: replied 4 years ago.

Installed the fuel pressure regulator, no change still wants to die at idle when hot.

Seems as if the fuel ratio goes off for some reason? Have swapped ECUs and no change, I actually have one of these vehicles myself.


I am out of ideas at this point not being there, I am going to let others view this and give it a shot.


Code 48 indicates a problem was detected with the IAC or idle control motor. Has this been checked?
Customer: replied 4 years ago.


Swapped it with the one from my car no change, idle motor seems to work.

So there was no change at all ?Also found this bulletin.
When a fault has been corrected, the fault code must be cleared. This is done by performing the following procedure:
Put the ignition switch in position II.
Disconnect the Data Link Connector (DLC) , which is located behind R/H side of dash, and wait 5 seconds. Reconnect data link connector.
Put the ignition switch in position 0 and wait till the load relay drops out.
Put the ignition switch in position II. The display will be blank if no other faults exist. If other codes exist, the next fault code will be displayed.
If multiple faults exist, repeat steps 1 through 4 until all faults are cleared. NOTE : Code 02 indicates that the Engine Control Module (ECM) has just been reconnected. Switch the ignition switch to position II to clear code 02.
Bulletin: W94-007
Section: Warranty (Revised)
Date: August 12, 1994
Model: ALL
Applicable to: USA/CND
Revision: To include additional information in step 3 and the addition of step 6.
Recent supplier test results have shown that a high percentage of Idle Air Control Valves (I.A.C.V) returned under warranty have no fault. Vehicle testing by engineers at LRNA of I.A.C.V's have resulted in the same determination. As of June 8, 1994, an I.A.C.V. will not be accepted under warranty by LRNA if it does not have a reproducible fault. To avoid warranty material being returned to your dealership, please consider the points below before - replacing any component.
1) Verifiable Defect
An OBD trouble code (DTC) 48 does not automatically mean a defective I.A.C.V. Code 48 is a DTC relating to the Idle Air Control System and not specifically the I.A.C.V. itself. A software strategy exists within the MFI ECM which, when certain engine running conditions are met, operates the M.I.L. and DTC 48. DO NOT replace an I.A.C.V. for DTC 48 unless the valve checks out as defective by the diagnostic procedure available in the Workshop Manual, Hand Held Tester Manual, or TestBook.
2) DTC 48 - Background
DTC 48 can be flagged as a result of an engine running problem which causes the I.A.C.V. difficulty in maintaining its target range of 665-735 rpm. An engine which has a fuel or ignition problem may suffer with a Code 48 because the stepper motor attempts to maintain the correct idle speed regardless of these other fuel and/or ignition faults. Code 48 occurs because of the idle speed control systems inability to maintain the engine idle speed within the target range. This can happen for two primary of reasons:
a) Air Leaks - Unmetered air passing into the engine resulting in the I.A.C.V. closing to more than 180 steps.

b) Overfueling - As a result of terminals, connections or ground connections problems. In particular ECM, 02 sensor grounds, 02 sensor signal connections or AFM circuit signal and ground wires.

3) Loss of Initialization
Some vehicles may suffer from a symptom of stall immediately following a start. This symptom is more apparent on a hot restart but can occur under any start condition. This stall occurs because the I.A.C.V. pintle "creeps out" from its correct start position prior to starting. As this "creep out" occurs it restricts the volume of air flowing into the engine via the I.A.C.V. system. This leads to the rapid drop in engine speed/stall immediately following a start.
The I.A.C.V. always moves against it's spring to the fully retracted position on vehicle power down. This action leads to the possibility of "creep" occurring. The amount of "creep" that occurs is related directly to the internal mechanical resistance of the I.A.C.V. If a customer complains of the above symptom it is acceptable to remove the I.A.C.V. spring. DO NOT remove the spring if there is no customer complaint. Only a small number of vehicles exhibit this problem.
4) Hand Held Tester Usage
When using the hand held tester to read I.A.C.V. position while setting base idle, on occasions the I.A.C.V. position is seen to:
- Read 180 steps regardless of base idle screw position.

- Please refer to E-mail 19-93/05 for guidance on this problem.
DO NOT replace the I.A.C.V.

5) Base Idle Recap
When checking or setting base idle as described in Service Bulletin P93/19-001, please note the permitted I.A.C.V. position range is anywhere between 135 and 165 steps. It is not necessary to reset the base idle if the I.A.C.V. is anywhere within this range.
Do not adjust base Idle if the I.A.C.V. is within this range.

6) I.A.C.V. Coil Resistance
When checking I.A.C.V. coil resistance, please be aware, DO NOT REPLACE the I.A.C.V. if the coil resistance reads between 40 & 70 ohms. Please amend all reference material which refers to any other resistance range and use this range.
This should help .Let me know if you need more assistance.
Customer: replied 4 years ago.

Car still dies at idle. We seem to have explored everything at this point.

Is it possible the FI wiring loom is backwards? I noticed there are only two circuits on the injectors if the right is on the left would it cause this probmlem?

No history going back very far on this car. Reason it came in this time was to replace the ignition pickup in the distributor. Car would not run.

Timing is right on. Car has good power.

We have to increase the idle via the cable adjustment so as not to trip the computer to code 48. that makes the idle high enough to keep running. Really baffled here

It possible try swapping them and see if there is a difference.Also make sure the mass air flow sensor is not damaged.Keep me posted.
Customer: replied 4 years ago.

We raised the idle speed with the throttle cable adjustment so as not to trigger the code 48, never did get the car to idle down? Oxy sensors were both dithering in range? We ran out of ideas and the customer needed to drive the car so we made it driveable and said we would keep thinking about it. My car will idle very slow now and then but keep running her's will not stay running when set to the factory settings.

may check back later Still thinking here


Ok I will do the same think this is a Throttle Body issue or it needs an ECM update..Keep me posted.

Customer: replied 4 years ago.

I tried the ECM from my car and saw no improvement.

I tend to think that the injectors might have a poor spray pattern and they might be dribbling instead of squirting. There does not seem to be a power problem, just will not idle slowly.

Also seems to be getting some oil in the coolant?

No particular coolant loss we can detect?

She is still having problems with it stalling

OK has compression been checked to rule that our as well as a faulty head gasket ?
Customer: replied 4 years ago.


Ok I would check these next to see if these can be a major pat of the issue you are having.Can you get this done and post the results here for me to diagnose?
Customer: replied 4 years ago.

In a word, no, she decided to sell the car. I fear that some poor quality work was done on the engine before she started bringing the car to us.


I have been down that same road before and trying to fix someones poor quality of work is like trying to solve a large puzzle.Well remember if you ever need any further assistance for anything at all jut let me know.Please rate excellent service so I can get credit for my help thanks.Bonuses greatly appreciated thanks.Bonuses greatly appreciated.
Tom, ASE Certified Technician
Category: Car
Satisfied Customers: 25954
Experience: ASE Certified Master Technician
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