[Kmsimonelic]

I have a 1988 Range Rover classic. Runs well except that at engine temps below 170ish the car emits a black smoke. At operating temp it doesn't smoke at all. Any ideas or thoughts?

 

[johnno42]

It's not burning oil? It might be running rich although I wouldn't expect black smoke - the ecu gets a temperature signal from the motor so it runs a bit richer while warming up and that could be playing up. Have you thought of things like oil dripping onto the exhaust while its sitting and then burning off while it heats up?

 

[Davehillbo]

Diesel or Petrol?

 

[Kmsimonelic]

It's standard unleaded gasoline not diesel and it's def not oil. It's a gray / black smoke so it seems to be running too rich at cold engine temps. I've replaced the temp switch (not the temp sending gauge) and nothing has changed. Could the fuel temperature sensor have anything to do with it?

 

[johnno42]

fuel temp sender only tells the ECU its a hot start. Shouldn't make a difference otherwise.

I've just worked through all the running rich options on my 90RRC (problem was the idle mixture was set way rich) and they seem to be:
Thermostat not warming the motor up (but yours is heating up)
Thermistor telling the ECU the motor is cold (should be about 200 ohms across the terminals at operating temperature, but if this failed then it would run rich all the time, not just when warming up)
Leaking diaphragm in the fuel pressure valve (Can test it by borrowing the long vacuum hose off the vacuum advance, hooking it up to the valve, suck hard and hold your tongue over the end and see if it holds vacuum, again if this was crook it would be all the time)
leaking injectors (pressure test or take of the rail and injectors, pressurise and inspect, similarly if they leak it would be all the time)
idle mixture set incorrect (on a 14 CUX the voltage test for the idle mixture should be 0.9-1.4 Volts, won't change with temperature)
Dirty MAF sensor (Buy a spray tin of MAF cleaner and clean the wires with it, but if its a crook signal it would run a bit rich all the time).

I'm assuming yours is a hot wire injection system. Nothing I can think of fits your symptoms but it wouldn't hurt to check some of the things on the list, you never know what you might find.

I'd be looking for oil leaks or oil consumption, it sounds like oil could be leaking into or onto the exhaust when the car is standing and then burns off when the exhaust heats up.

 

[Kmsimonelic]

Thanks for all of the helpful advice. it's def not oil. You can smell the rich mixture and unburned fuel in the engine exhaust. There is no burning oil smell at all. Could the ECU itself be messed up?

 

[johnno42]

I'd be inclined to think not, its all solid state. You should be able to find someone who can get an error read out from it, again it depends on the system you have, the module is under the passenger seat (left hand drive) and it should have a label on it saying what it is. If its a 14CUX there maybe an error message module as well and you can check that for codes. If you want to reset it, you can either disconnect the battery and wait a while, 10 secs on a 14CUX, or pull the connector on the ECU and wait for ten seconds. Nothing makes much sense to me from what you describe. I'd suggest you work through the various items one at a time and check them off.

There is a good article on the 14CUX system here:

http://www.actproducts.co.uk/2011/l...n-system-–-installation-and-diagnostic-notes/

Also you might have O2 sensors and a catalytic converter. I don't know much about these, but I would think a crook O2 sensor might result in rich running.