Rough Running at Part Throttle
Discussion
My 96 500 has started to shunt at low revs & unhappy at anything other than heavy throttle.
Having replaced most of the ignition system this year as preventative maintenence i'm struggling to identify the fault.
Engine air & mixture tuned last month with new coil, plugs, leads, dizzy, rotor, & temp sensors, ignition amplifier replaced. New fuel filter & lambda sensor also changed.
With Le Mans looming I'm struggling to identify why suddenly its started doing this.
I did change 4 relays (footwell 12v 30 amp) the day it occurred but i can't see this having any correlation.
The only missing link is plug extenders last changed 2006 for which supply has dried up so i can't replace these at present.
Anything i've missed or potential causes appreciated?
Having replaced most of the ignition system this year as preventative maintenence i'm struggling to identify the fault.
Engine air & mixture tuned last month with new coil, plugs, leads, dizzy, rotor, & temp sensors, ignition amplifier replaced. New fuel filter & lambda sensor also changed.
With Le Mans looming I'm struggling to identify why suddenly its started doing this.
I did change 4 relays (footwell 12v 30 amp) the day it occurred but i can't see this having any correlation.
The only missing link is plug extenders last changed 2006 for which supply has dried up so i can't replace these at present.
Anything i've missed or potential causes appreciated?
Did you replace relays with genuine Bosch, I believe anything else won't work properly (mine didn't). Also worth checking & cleaning the stepper motor, maybe check the throttle potentiometer settings. Is induction system ok, air filter, AFM (if fitted) etc. Fuel pressure, flow - it could be one or more of lots of things - sorry. Do you have Rovergauge or ECUmate, might help in diagnosing or at least elimination ?
Seems to be a common problem! Have a look at my thread here;
http://www.pistonheads.com/gassing/topic.asp?h=0&a...
HTH
http://www.pistonheads.com/gassing/topic.asp?h=0&a...
HTH
Andy JB said:
My 96 500 has started to shunt at low revs & unhappy at anything other than heavy throttle.
Engine air & mixture tuned last month with new coil, plugs, leads, dizzy, rotor, & temp sensors,.....
Anything i've missed or potential causes appreciated?
Love to know how the Engine air and mixture was adjusted when you cant adjust it- this sort of thing bothers me as it sounds like dealer speak for justifying the bill....Engine air & mixture tuned last month with new coil, plugs, leads, dizzy, rotor, & temp sensors,.....
Anything i've missed or potential causes appreciated?
Anyway- try unplugging the AFM and see if its the same- a broken AFM connection will give these symptoms when the ECU is in fall back mode.
Blitz,
Should the AFM in these cars be considered a service item? I have no reason to doubt my AFM, it appears to be running fine but The originals will be 15 to 20 years old in our cars and would have been subjected to a fair bit of heat.
If they lasted that long, is it worthwhile replacing them as it's a case of when rather than if they go wrong?
Should the AFM in these cars be considered a service item? I have no reason to doubt my AFM, it appears to be running fine but The originals will be 15 to 20 years old in our cars and would have been subjected to a fair bit of heat.
If they lasted that long, is it worthwhile replacing them as it's a case of when rather than if they go wrong?
Thanks some things to check here - AFM has never had any issues to date but as you point out they are now 15-20 years old.
Never heard of the rotor arm being too low but worth a try.
The car has been running perfectly since these changes a few months back. The relays were indeed genuine Bosch items but it does seem a lot of coincidence, strangeley some i changed were aftermarket ones over 10 years old. Problem is I'm not sure what they all do as no mention in manual or Steve Heath, so perhaps i will change some back for time being, except fault seems intermittent which doesn't help.
...and i thought i knew everything on these engines after 10 years of maintenance....
Never heard of the rotor arm being too low but worth a try.
The car has been running perfectly since these changes a few months back. The relays were indeed genuine Bosch items but it does seem a lot of coincidence, strangeley some i changed were aftermarket ones over 10 years old. Problem is I'm not sure what they all do as no mention in manual or Steve Heath, so perhaps i will change some back for time being, except fault seems intermittent which doesn't help.
...and i thought i knew everything on these engines after 10 years of maintenance....
A900ss said:
Blitz,
Should the AFM in these cars be considered a service item? I have no reason to doubt my AFM, it appears to be running fine but The originals will be 15 to 20 years old in our cars and would have been subjected to a fair bit of heat.
If they lasted that long, is it worthwhile replacing them as it's a case of when rather than if they go wrong?
Any electronic circuit will fail faster if you keep heat cycling it. Getting a decent second hand spare of a Range Rover (that does not cook it)- would seem like a good idea.Should the AFM in these cars be considered a service item? I have no reason to doubt my AFM, it appears to be running fine but The originals will be 15 to 20 years old in our cars and would have been subjected to a fair bit of heat.
If they lasted that long, is it worthwhile replacing them as it's a case of when rather than if they go wrong?
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