Does not stay running in gear cold
 

OK, so this problem sprung on my 3 days ago...

When I start the disco, it runs just fine. Once it warms up a little and when the idle drops, I can't keep it in gear without it crapping out. It's acts almost like a manual and it stalls and dies when I come to a stop (but with out the bucking and jumping). I have to shift to neutral when I come to a stop.

Once I get it nice and warmed up, it works great. But I mean SERIOUSLY warmed up. Not just the temp gauge at 9:00. I mean driving around for 20-30 minutes type of warm. The rest of the day is fine. I drove at lunch time and then again to go home. No issues.

We have had 3 rather brisk mornings and the first to were also pretty wet. I was thinking that maybe something got wet, but today was dry and still the same business.

Its a '96 Disco, ODBII, newish plugs and wires, always had premium fuel (as long as I have ad it) and it's not throwing any codes. I am thinking that there might be some sort of idle control module. Otherwise I have no idea to start.

I took a quick peak under this hood this morning at work. Nothing obvious; vacuum hoses, disconnected plugs, etc.

The idle is controlled by the IACV (idle air control valve). You remove it from the throttle body, and spray clean it with carb cleaner. Don't wiggle the pintle, the electric stepper motor will move that. Also clean the bore it comes out of.

If you have a live data scanner you can also check you coolant temp, the sensor that drives the ECU is separate from the one that drives the gauge. Should be a logical value (like ambient) to start, then warms up.

I will check out that valve this weekend. I imagine something as simple as dropping a can of seafoam in the tank and driving it 20 miles wont work?

I am curious if it is a sensor, and if it is where would I find it? The reason is because I drove it about 5 miles last night and it sputtered and stalled at every stop. It stood for about 2 hours. Then it drove great for the 5 mils back. What I observed is that the gauge showed that it was cold on the second start, however the heater blew decently warm air. This is telling me that the motor was still a bit warm.

You need to buy/rent a OBDII scanner and watch the live data, it sounds to me like the ECU thinks it is already warmed up and it is running to lean when cold.
This would be because of a bad coolant temp sensor.
The 3.9 uses the same sensor for the ECU and the gauge, that would make sense as to why your temp gauge read cold but you had heat.

I'll agree with Spike on the issue (bad sensor), but the RAVE schematic shows two separate sensors and connectors (C152 and C151). And while it can be a bad sensor, it can also be a skinned wire in the harness or gunk on the connector, anything to make resistance look like something else to the hardworking ECU. A live data scanner can show you what the ECU sees, and if it is not logical (like +169F at cold start in morning, or -40F in afternoon, etc.) then you are on the right limb of the shade tree.

Does this look like the right one?

SENSOR COOLANT EFI DEFENDER, DISCO I, P38A, RNM134, ETC8496 - Rovers North - Classic Land Rover Parts

Yup, thats the one.

I don't know how Savanna does it, but he gets it right on the first try...

I got home last night with about 10 minutes of daylight to spare and I cleaned up the ICV with a little TB cleaner and a q-tip. Took it out later for a quick right and it drove like a champ. It will take a few more trips for me to gain my confidence back, but the ball seems to be bouncing in the right direction.

I think I will still get the laptop out and look at the live data however....

The problem returned after just a few days of blissful trouble free driving... I installed my Car-Chip and logged some data. Below are the temperature plots of my last three cold starts, each of which experienced this problem where it would stall when I come to a stop.

The odd thing that I notice is that once the problem starts, it appears to stay until the disco is parked and turned off even for a short period of time. On one trip while experiencing the problem, I drove about 2 miles and made my usual stop for coffee. But instead of going through the drive through, I parked and walked in. I was in and out in less than 5 minutes and she fired right up and continued on with no issue....

This morning, I started the motor and let is run for 10 minutes and still experienced the problem.

3 trips of 7, 9, and 15 minutes and in each instance, the problem persisted until it was turned off for a short period of time and started back up.


Attachment 39473

Attachment 39474

Attachment 39475

That looks like a fun gadget. If it improved when you cleaned the IACV, but returned...

Perhaps the PCV system is also clogged and causing IACV to get more gunked. On passenger side valve cover is a vac line from the oil separator to the intake. Pull out separator (squiggly plastic noodle) and de-gunk. Then on driver side find line from valve cover to the throttle body. It does not have a separator. Normally filtered air from is sucked into the driver side valve cover, passes through the valley area, and out the passenger side to be burned in the engine. Under certain conditions the flow is the other way, thru the valve cover with oil-laden vapor and into the throttle body. I pulled mine out and cleaned down inside the bore with a Q tip soaked in carb cleaner. It was a lot of buildup, and vehicle ran better afterwards.