I have an 1988 Land Rover Range Rover, 3.5 L V-8, 4 speed automatic, approx. 150K miles. When the weather starts to cool down (that is, 50’s at night, 70’s during the day and colder), my car will start to develop a stalling problem. As I slow down to below 10 mph or stop, it will stall about half the time. It does it whether I am braking or not (ie. drifting to a stop). I have tried shifting into neutral as I approach a stop. This seems to help a little. It happens more and more frequently as the weather gets colder. I rarely drive on the interstate but when I do, it tends to stall as I exit and slow down to under 30 mph. No check engine light or other warning lights come on (aside from the battery light as it stalls). The problem has been getting progressively worse - stalling more often and in warmer and wamer weather. The only thing I have done in an attempt to fix it is to get a higher amp. battery than recommended. The first time it did this, I was driving on a fire road in the mountains in low gear with the differential locked in and a very slow speed. Thanks for your help!
Oh, this one I know. I have a 1990 3.9 efi.
This is either the Throttle Position Sensor or the Idle Air Bypass Valve. Neither of these parts are cheap.
If you own an old RR your best sources of info are :
My problem was the TPS, it has limited adjustment and has to be set with an ammeter, but you can cheat it slightly if it’s marginal.
Any way to tell which it is? For instance, can I take one or the other off and test it somehow?