96 Disco Confusion...
 

Ok guys - I'm a little confused. I think that I might have researched the forum a little too deep and am overlooking the obvious.

First : 1996 Disco SD with the 4.0L Auto/Air
235K Miles - 2nd owner
ELM327 OBDII Bluetooth interface with Droid Phone

Now the problem - it's going to be wordy because I'm trying to cover all the bases.

When I start the Rover it idles at 850rpm until it warms up, then drops to 625 and idles just fine. nice and smooth, with or without the A/C on.

When driving it runs good, smooth accelerations and stays on the mark with the cruse control on.

I run an OBDII interface 24/7 and monitor the temps. They are fine and it shows no codes.

That's what happens about 80% of the time.

The other 20% it will be idling, and just shut down. No warning. Like turning the key off. Hit the starter and it fires right up. No codes shown.

Running down the interstate at 50mph with the cruise control on, it will decelerate, like the switch was turned off, for just a second, then be back to normal. The cruise control never stops. no warning lights on the dash. no codes.

Same thing without the cruise control. I can feel it decelerate briefly and then back to normal.

When I start it and let it run cold...I can be under the hood and it will high idle for just a minute or two, then drop to the normal idle. It can stay like that for the entire time I am there. Other days it will idle for about 3 minutes and then shut down. There is no gas smell like it's flooding. And it starts right back up.

I know - I have over analysed it and probable confused everyone. its the OCD kicking in!

Help me Obi an Knobi - you my only hope!

Vehicle speed sensor is my first inclination.

Ditto

This may show up as unusual mph variations on your scanner. The dash gauge has dampening and you might miss that.

Well thanks guys. Kinda what ivwas thinking but this is all new to me.
Sent a request to paul through hos website for a price on a used vss. At $187 for a new one from AB i can live with the dedeleration issue for a while.

If you have an alternative speed over ground indicator, like a GPS, you could unplug the VSS for testing (cruise will be out also).

Sooooo...

If I disconnect the VSS I will lose the cruise control and speed-odometer?
That's all? Will it throw any codes?

Sounds like a plan when I get home this afternoon...I'm going to be under there with the grease gun looking for zerkes anyways!

Well last week I was under the Rover and hit the Zerkes with some grease.

While I was there I un-connected, cleaned and re-connected all the connectors I could find on the transfer case and transmission.

Haven't had a problem since. Maybe I got it for once?

Oh - and I probably just jinxed it for me on the way home!

My 95 just started doing the same thing. I was assuming i was having a fuel pump issue since it would just randomly turn off

Well I did it. Jinxed BIGTIME

Drove to work this morning...no problem. Nice idle smooth ride.

Went to leave work at 4pm and NOTHING.

She cranks and turns over.

The immobilizer appears to be working correctly = doors lock / unlock ect.

She has 1/2 a tank of gas.

She has good spark on both banks.

Tried resetting the fuel cutoff on the passenger side of the engine firewall.

Checked and switched out the fuses under the hood for the fuel system.

Cleaned and pushed the hood alarm button on the fender near the battery.

TURN THE KEY TO START AND CHECKED THE FUEL RAIL NIPPLE WITH MY POCKET KNIFE - IT WAS BONE DRY.

That was the extent of my fiddling till I had to leave.

That is the last time I boast about anything!