Well, I swapped mine ( ECU and IACV ), but did not swap the alarm on my D1. Did not have to visit the Testbook. But agree on drive cycles, and that would be drive, cool off, restart, drive again, not just five short key on/crank/off, repeat.

 

I'm no expert, just going by what others have told me and my own ECU experiences. AFAIK the two are tied to the vin and hence to one another. Only one other I've talked to was able to swap ECU without the alarm and it worked. He couldn't explain why and he is the type to know why. He changed out a few that he had on hand until one worked. I'm not so lucky as you two.....I had to have both to make it work. I swapped a 97 pre AES to a 98 AES box. I also had to have the variables reset in order to get the IAC values to stick. See how unlucky I am?

 

OK Here's the thing, I called my Rover indie Ian Campbell- great guy ex Range Rover Service manager in Los Angeles, described the symptoms - he said that at 2,000 RPM there is no way an ECU reset will solve that, too big a leap, something else is going on. So on further discussion bought a Coolant Temp Sensor.

Started the disco to move it to the garage, idled @2000 as usual, put the sensor in, she idled beautifully at 700 ran it for 15 minutes till the thermostat opened - fantastic!

Stopped the engine and went to fetch my wallet to go fill up with gas, started her and back to 2000 on restart. WTF??? Nothing I do will bring that idle down. Any other suggestions? Anyone? Because the way I feel now, either she or I are going down.

 

On the intake near the upper radiator hose are a two wire and a single wire sensor, they are coolant temp, 2 wire goes to ECU, single goes to temp gauge.

When I first purchased my well used D1, it did the same thing, and I replaced the ECU and the IACV at the same time to finally get it down to normal. Both pieces came from a donor vehicle. I had tried a number of ways to make the ECU "memorize" the new IACV each time I changed it, and I guess I was just not getting it, or my original ECU was not giving up memory of the original IACV. ECU was $40 at salvage yard.

I also wanted to ask about having to reset the ECU with a Testbook
as I had been led to believe was necessary unless the alarm ECU was also acquired.

Or do you have the alarm bypassed or disabled in some clever fashion?

 

Isn't there also an air temp sensor as well as the coolant temp sensor that provides input to ECU? I remember reading somewhere that the air temp sensor can cause same problem.

 

Yes there is also a air intake temp sensor, it is in the airbox.
Intake air temp, engine temp, tps as well as O2's and MAF all tell the ecu how much fuel the engine needs.
If you recently worked on the truck and had the intake off or any other sensor or vacuum line then you need to double check your work.
If ti was fine before adn not now, it has to be something you did or did not do.

 

Thanks I get all that, but the car idled perfectly when I fitted both the new plenum and now the new coolant sensor.

On both occasions when I stop it for 4 minutes get back in and it idles through the roof. That's the part that makes no sense. Something in turning the car off and on again is resetting either the ECU or IACV. The other sensors on (according to Rave) affect the richness and that is not going to make the car idle at 2000 rpm.

 

By the way when i get back in and start I'm not touching anything other than the ignition key.

 

You may have a broken or loose wire at one of the sensors. If you plug in a data reading scanner, an "open" cable to a coolant or air temp sensor will make scanner read "minus 40" for temperature. Such a condition would increase fuel to compensate for extreme cold. Would be good if you had scanner on truck when doing the warm start. The fuel temp sensor would also be suspect (it is monitored to deal with warm starts). And yes, too rich is exactly what increases idle speed.

Turning the truck off allows underhood and engine temps to rise. Coolant sensor and fuel temp sensor will both be warmed up. Air temp sensor is somewhat isolated, but will still see an increase. A bad sensor or connection could be heat sensitive, going open or way out of range when warmed up under hood of stopped truck.

Do you have a scanner available, even if you have to promise to Simonize a buddy's Jeep (eeek - Jeep on my hands!)?

 

Thank you. A loose wire is my guess as well. I read another forum where the guy found a loose 5v wire to the TPS which was causing exactly the same problems as me. What should I buy, what do I need in a scanner ( I have an OBD but basic) What you are describing sounds very expensive? I don't know anyone with one - i am the only one mad enough to own 2 land rovers amongst my friends.