Well, my diagnostic box finally started showing a code for the rough idle/low rpm hesitation/hard hot starting I am expereincing. It is showing code 48, I believe this is for the Idle Control Valve. I removed it ant cleaned the plunger also removed and cleaned the housing for it as well as checked obvious vacuum hoses and the intake boot. Any ideas?

Jeff M.
Columbus, OH

 

You might also take some carb cleaner and clean the inside of the throttle body, throttle plate and throat. Spray it good scrub with a tooth brush if necessay and wipe out with a paper towel.
This will assure you that the throttle plate is not sticking causing more air then normal at idle.
Mike

 

Thanks for the fast reply Mike! I'll give that a shot today.

I am an experienced VW/Audi/Porsche/Saab Tech, but this Land Rover stuff is a little different.

Jeff M.
Columbus, OH

 

So True!!

 

Well, cleaning the Throttle Body did not change any symptom. Any reason for me to remove the intake manifold (possibility of clogged ports?)

 

I've had the same problem as you did... I had the whole throttle, intake, stepper motor and stepper motor housing cleaned and I was still getting a code 48. About a week ago, I had the vacuum hose connected to the stepper motor housing replaced and the thin hose that leads to the vacuum advance replaced as well. This definitely helped with idling...but code 48 kept on coming back. Yesterday, I took the stepper motor out and found most of the plunger sitting inside the motor. I attempted to pull it out a little bit, but it was hard because it felt stuck. I greased it a little bit with wd-40 (very little) and slid the plunger in and out until the plunging movement was freed up. After I reinstalled the stepper motor (with the plunger slightly sticking out), I had the base idle readjusted. It's been over a day now and I haven't gotten code 48 back yet.
To set the base idle, you need to start the truck and let the idle settle down. I did it when the truck was at operating temperature...not sure if it makes a difference. I then used a flat-needle nose vise grip and clamped the bypass air hose shut. This is the vacuum hose that leads into the throttle and the stepper motor housing.The hose is approximately 1 inch thick and it is between the throttle body and the firewall. After you clamp it shut, adjust the idle by using an allen key. The idle adjuster is on top of the plenum. Adjust the idle till it drops down to about 525 rpm. The best is to use an external tach. I didn't have one, so I had to guess my rpm from the dash. The car will feel like it wants to shut down. After you reach this goal, release the vise grip and the truck should idle higher and the computer will slowly adjust to it normal range. After the truck is idlingnormally...about 5 minutes or so...shift from Park to Drive, Drive to Reverse, Reverse to Park, Park to Reverse andcarefully notice your idle. If the car stalls, thenre-do theidle adjustment process. Turn the idle higher by a quarter inch, then release the visegrip and let the car idle now again. Repeat the process as necessary until the truck does not stall. You probably won't need to redo this process if you have an accurate external tach. Then try to shift again and see ifthe truck stalls. When ever the truck shifts, there is asplit second drop in rpm...if it drops too much then the idle is too low.
When I released the vise grip, the idle was slightly higher and I let it idle for about 10 minutes. After that I took it for a spin,I pulled over and shifted to park. The idle shot up to 2000 rpm, then 1500 rpm, then finally adjusted back to normal idle range. Hope this help. If you adjusted the base idle and code 48 is still there, then you may need a new stepper motor.