I've noticed a strange issue during the last few starts of my 01 Discovery. It cranks fine and after a few minutes of running, usually as soon as I back out of the drive-way, there is a quick shutter or stall like noise and feeling in the throttle/idle. I also notice after this happens my UltraGuage reads 'Error' for readings. I'm able to stop and restart the vehicle and it clears the UltraGuage and doesn't happen again. This usually only happens on the first start of the day.

Because the UltraGuage shows error I have a feeling it is ECU related, but I have no other apparent issues or warning lights/alarms. Any ideas?

 

That's right around the time the SAI pump shuts down. Maybe one of the valves is sticking open, or something like that? It might be worth checking out anyway.
Maybe you could even try disconnecting the vacuum lines and plugging them. Then see what happens on a cold start. If you don't get any different results, maybe try unplugging the control solenoid and see if that changes anything??

 

I don't believe I have SAI. I also forgot to mention it has had a little trouble cranking lately, and yesterday I had to jump it off. I just replaced the battery a few weeks ago so I dont think it's that. Would that indicate an alternator issue? Maybe an electrical issue was causing the ECU to hiccup?

 

I thought a about the SAI after writing that. I was just trying to think of things the truck would be doing after that amount of run time.


Check your battery cables. Check the terminals at the battery and check the grounds especially. Bad grounds can cause all kinds of trouble. They can definitely cause starting and charging issues.

 

Suggest first checking batt with a meter after sitting overnight, it should be about 12.6vdc if it's good and alt doing job. D2s are known to have some low voltage related issues.
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Number9 makes a good point. If you suspect a charging issue, you can also check the battery voltage at rest and with the engine running. It should be about 12.6 volts with the engine off, after sitting overnight, as mentioned. With it running, you should see somewhere around 14 volts or more.

 

Just following up on this item... After jumping the Rover I've tried to make a better effort at cranking it up more often, and I haven't had the same issue. I do notice at least from my UltraGuage that voltage starts about 14 but it usually hovers around 13.5 while I'm driving.

 

That sounds like pretty decent charging voltage. The higher voltage on startup is probably because the voltage is a little lower after sitting. So the charging system puts out a little more initially to get the voltage to a certain point. After it gets the voltage to a certain level, it will back off and maintain a steady voltage.
I have jump stated cars with dead batteries and put a meter on them immediately after. Sometimes the voltage goes up to 15 volts or higher as the computer tries to get the voltage up. That's why cars with a voltage gauge will sometimes show higher voltage when the battery goes bad. It can't hold a charge, so the computer starts working the alternator harder trying to bring the charge up.