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Discussion Starter · #1 ·
If I place my '94 LWB EFI 4.2L V8 RR Classic into neutral while coasting at low speed, The tachometer shows that the engine is bouncing between 1300 to 1600 RPM's back and forth erratically. If I unplug the connection to the Air idle control motor, the engine idles at 3,000 RPMs.

The Air Idle Control Stepper motor was replaced not too long ago. The O2 sensors have been replaced as well. My electronic traction control light is on. I dont know if that is related to this problem or not. Anyone ever see this?
 

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Erratic idle

I have had a similar problem with my Discovery V8i (1996). The fault is intermittent, sometimes just irritating and sometimes leads to stalling. The rev counter swings from about 1300 to about 600 and sometimes down to zero. I have noticed that it does not happen at higher revs and rolling the car down a hill (not under power) abolishes it. There is a smell of unburnt fuel and fuel consumption goes up drastically. My local Land Rover majician has done everything he can think of but the problem comes back. We even replaced all of the electronic components at one time using canabalized parts from a damaged Discovery. Sometimes his computer shows a fault with the stepper motor but replacing it did not fix it. Any suggestions?
 

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Patrick MacPhail said:
I have had a similar problem with my Discovery V8i (1996). The fault is intermittent, sometimes just irritating and sometimes leads to stalling. The rev counter swings from about 1300 to about 600 and sometimes down to zero. I have noticed that it does not happen at higher revs and rolling the car down a hill (not under power) abolishes it. There is a smell of unburnt fuel and fuel consumption goes up drastically. My local Land Rover majician has done everything he can think of but the problem comes back. We even replaced all of the electronic components at one time using canabalized parts from a damaged Discovery. Sometimes his computer shows a fault with the stepper motor but replacing it did not fix it. Any suggestions?
Hi Patrick,i don't mean to teach grandma to suck eggs but have you reset the base idle correctly? Disconnect the stepper connector,then the large black pipe to stepper housing and plug both openings.You are now able to set the base idle speed without ecu interference(hex screw in top of throttle housing).I would recommend approx 600-620 rpm.Reconnect the pipe and plug and Robert should be your Mothers brother.
****.
ps. the stepper fault code 48 is logged purely because the ecu tries to control the idle but fails,so it logs the fault with the idle speed component,hope that makes sense
 

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Discussion Starter · #6 · (Edited)
Surging Problem Fixed

Serg said:
You might have a vacuum leak somewhere in the engine bay...


Serg
Thanks Serg,

I replaced all the PCV tubing and vacuum lines and incindently I found a loose connection on my engine temp. sending unit (mounted near the base of the intake manifold) and the truck runs like dream. The O2 sensors were replaced because of an engine fault identified by a garage, not because of the surging.

Kornhagr
 

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Discussion Starter · #7 ·
Patrick MacPhail said:
I have had a similar problem with my Discovery V8i (1996). The fault is intermittent, sometimes just irritating and sometimes leads to stalling. The rev counter swings from about 1300 to about 600 and sometimes down to zero. I have noticed that it does not happen at higher revs and rolling the car down a hill (not under power) abolishes it. There is a smell of unburnt fuel and fuel consumption goes up drastically. My local Land Rover majician has done everything he can think of but the problem comes back. We even replaced all of the electronic components at one time using canabalized parts from a damaged Discovery. Sometimes his computer shows a fault with the stepper motor but replacing it did not fix it. Any suggestions?
Check out my reply to Serg in this same thread. The damaged connection was only identified
after I peeled back the rubber insulation around the connector itself. Let me know if you figure this issure out. Good luck.
 
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