High calculated load at Idle & High fuel consumption
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Thread: High calculated load at Idle & High fuel consumption

  1. #1
    FRESHMAN ROVER
    Join Date
    February 24th, 2011
    Posts
    7

    High calculated load at Idle & High fuel consumption

    Hi guys, I need expert help.
    Can anyone help me adjust something to get my Calculated load Value to go down from 24% at idle to (2.8%-3.8% book specs.)
    Does anyone know how the Calculated Load Value is derived by GEMS ECM, which sensor inputs are used for this, that may point me in the right direction?
    Also does anyone know how to set the base idle? My plenium screw is open 1 turn counterclock wise.
    To give more information, below are the reading for my GEMS 4.0 at normal operating temp taken with MSV-2 Extreme. note: some cold values that are odd are also included.

    Symptoms:
    No fault codes
    High fuel consumption & lack of power
    - The vehicle message center reports fuel consumption of 24.6L/100. This vehicle is usually driven conservatively and the sports mode is hardly ever engaged. This is a average of city and highway driving. On a recent long trip I noticed that the fuel mileage did not improve much even at highway speeds with premium high octane fuel.
    - The engine seems sluggish and gutless. In fact on long steep uphill section of the highway (6% Grade) this vehicle used to maintain 120 kph with little effort, but recently second gear and pedal to the floor just to maintain 80 kph.
    Occasionally rough, very low idle when restarting from hot.
    - If you shut off hot engine and restart within a couple of minutes. It starts fine (with no pedal revs to 1100 and settles down to 700rpm).
    - It starts fine if you start after being off for an hour
    - If you shut off hot engine and come back about 15 - 20 min the car starts, revs to 1100 and then drops to probably 300 – 400 rpms and runs rough. When you rev up the motor a couple of times it settles into proper idle. Sometimes it takes a few more rev ups to get normal idle.

    MSV-2 readouts / Normal operating temp. All adaptive values were reset two weeks ago.

    Description Warm Engine Comment
    Intake Air Temp. 19 C -12 C Cold Engine Ambient 7 C ??!! Why?

    Calculated Load Value 24%@700rpm 38%@940rpm Book Spec. 2.8% to 3.8% @ 700rpm & 10% @ 2500rpm ?????!! why?
    Fuel trim Long T. 1.2
    Fuel Trim Short T. +1.5 to neg.-2.5
    Long T. Adaptive Idle 253 steps ??? Is this ok
    Short T. Adaptive Idle 255 steps ??? Is this ok
    Throttle position Curr.0.67v, Str.0.66v OK
    687rpm to 711rpm OK
    Mass Air Flow Sensor 1.39v, OK
    Current Air Flow 21kg/hr@695rpm OK
    61kg/hr@2750rpm OK
    Adaptive Air Flow 0.3 kg/hr OK
    Idle Air Control 20 steps OK
    Current Run Line 20 steps ?
    Engine Coolant Temp. 96 C OK
    Ignition Timing Ad. 27.5deg – 28.5deg ?
    Current G.box Retard 17.2% OK
    GEMS Status Closed Loop O2 Both Banks
    Pre-cat O2 Bk.1 0.1v - 4.75v Bk.2 0.12v - 4.87v OK
    Post-cat O2 Bk.1 2.12v – 4.17v Bk.2 3.4v – 4.4v OK

    Pre-cat Heaters 0.97v – 0.99v
    Post-cat Heaters 0.94v – 0.95v

    Thank you all for reading my post.
    Kevin

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  3. #2
    FRESHMAN ROVER
    Join Date
    February 24th, 2011
    Posts
    7

    Re: High calculated load at Idle & High fuel consumption

    Ok. So no one is willing to take a stab and check the readings that I got from the MSV-2. Is there someone out there that can give me the normal readings from a healthy 4.0SE GEMS? Perhaps point me in the right direction to find the factory specs. for these reading. I will be greatly thankful for any hlp at all. Thanks,
    Kevin.

  4. #3
    SENIOR ROVER rtkraken's Avatar
    Join Date
    July 23rd, 2005
    Location
    Midcoast Maine USA
    Posts
    1,067

    Re: High calculated load at Idle & High fuel consumption

    BBS has some information on what should be normal, in their system software package descriptions/information. Also RAVE has some limited information on sensor readings in Fuel System Sect 19, pgs 16 and 17.
    I see you haven't mentioned the fuel temp sensor. If it's bad GEMS gives it a default 40C. I just replaced mine and got a very surprising and significant increase in fuel economy. Before this I had thought it was merely to effect fueling at start up.

    Most of what you have looks OK (from memory). The Adaptive idle seems a bit out, but this is a GEMS response to something else. Should be pretty easy to unscrew the air intake temp sensor and confirm it's operation.
    92 Classic (retired) 95 Classic (150K) 95 4.0 SE (160K) 96 4.0 SE (200K)
    07 HSE L322 (70K) 02 4Runner (safety net)

  5. #4
    Premium Member
    Join Date
    February 21st, 2010
    Location
    W.Midlands UK
    Posts
    2,443

    Re: High calculated load at Idle & High fuel consumption

    what about the mechanical condition\history?
    the load iirc is derived from the maf sensor alone, are you sure the clv values your quoteing are right, to me one of them at least look's suspiciously like decimal place error 3.8% and 38% - 2.8% and 24%???? Just my take.
    the engine bay is a very hot place in a v8 rover, i've measured temps well over 50 C in the engine bay by the intake box whilst driving (via an independent thermocouple) so don't be surprised by that difference.
    Rave shows at 2500 rpm maf should be 60kg\hr +/- 3kg, so obviously it could be as low as 57 or as high as 63 to be within range.
    Larry S
    1995 4.6 HSE

  6. #5
    FRESHMAN ROVER
    Join Date
    February 24th, 2011
    Posts
    7

    Re: High calculated load at Idle & High fuel consumption

    Hi Guys, Thank you for giving me some response on my dilema. I have had this vehicle since new and it has had meticulous care. It has had Syntetic oil changes every 5000K. Trans syntetic every
    10 000K. Radiator flush every year. Hoses , belt, platinum 4 plugs, K N air filter, Ultrasonic injector clean, Borla exhaust, Gen III Arrnott air springs, Belistien shocks, Optima Battery and lots more.
    I just took compression first compression stroke between 7.5 to 8 and compression after three strokes of 10 on all cylinders. All the reading posted are correct and yes surprisingly 24% load at idle. These readings are not only from MSV-2 but also from a second engine anylizer as well. fuel consumption of 24L/100k which does not improve much even on the highway doing 100k. No air or vaccumm leaks. Purge valve seals when engine is off and pulses with the engine running. Crank case ventilation clean and unpluged both sides. Correct valve lift on all valves measured from the rocker arms.
    I am now thinking Catalytic convertors may be plugged. however O2 data does not support this. I am going to take a pressure measurement from the pre cat O2 sensors. If the cats turn out to be ok, what else could it be? Could it be faulty ECM?

  7. #6
    JUNIOR ROVER Escape's Avatar
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    June 4th, 2007
    Location
    Belgium
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    935

    Re: High calculated load at Idle & High fuel consumption

    Have you checked the timing chain is still nice and tight? They do wear with mileage.
    4.0 SE manual, 1995, 'Piper': daily, GENIII, 4.6
    4.0 SE manual, 1997, 'Priscilla': new addition
    4.6 SE auto, 1995, 'Prue': GF daily, now 4.0
    2.5 DT manual, 1996, 'Paige': retired
    D90 TD5, 2005, 'Nessie': TR2 racer

  8. #7
    FRESHMAN ROVER
    Join Date
    February 24th, 2011
    Posts
    7

    Re: High calculated load at Idle & High fuel consumption

    Hi ESCAPE,
    No I have not checked the timing chain. That is a very good possibility. It used to be so easy to do a timing chain check on cars with distributors. I guess with the valve covers off I could turn the crank until one of the valves it at full lift and then turn the crank the other way and see how far I have to back up before any movement can be seen on the valve. I thank you for taking the time to help me with your wisdom. I will do the check and will get back to you all. Thanks to all that have helped me.
    Kevin.

  9. #8
    Premium Member
    Join Date
    February 21st, 2010
    Location
    W.Midlands UK
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    2,443

    Re: High calculated load at Idle & High fuel consumption

    has the K&N filter contaminated the MAF and is MAF genuine Lucas?
    Larry S
    1995 4.6 HSE

  10. #9
    JUNIOR ROVER Escape's Avatar
    Join Date
    June 4th, 2007
    Location
    Belgium
    Posts
    935

    Re: High calculated load at Idle & High fuel consumption

    Quote Originally Posted by Kevin
    Hi ESCAPE,
    No I have not checked the timing chain. That is a very good possibility. It used to be so easy to do a timing chain check on cars with distributors. I guess with the valve covers off I could turn the crank until one of the valves it at full lift and then turn the crank the other way and see how far I have to back up before any movement can be seen on the valve. I thank you for taking the time to help me with your wisdom. I will do the check and will get back to you all. Thanks to all that have helped me.
    Kevin.
    Easiest way to check the timing chain is to remove the sump. Putting it back is easy as well, only downside is you need to clean everytinh before applying sealant...
    4.0 SE manual, 1995, 'Piper': daily, GENIII, 4.6
    4.0 SE manual, 1997, 'Priscilla': new addition
    4.6 SE auto, 1995, 'Prue': GF daily, now 4.0
    2.5 DT manual, 1996, 'Paige': retired
    D90 TD5, 2005, 'Nessie': TR2 racer

  11. #10
    FRESHMAN ROVER
    Join Date
    February 24th, 2011
    Posts
    7

    Re: High calculated load at Idle & High fuel consumption

    OK. Now I have removed the sump and checked it out. I turned the crank until I had all the slack on the side that I could see and between the camgear and the crankgear from what I could tell the is a 10mm to 12mm or about 1/2 inch or less slack in the chain. What is the normal amount of slack?
    I also observed that there was a white color residue in the sump directly under the timing chain. Is this some sort of coolant leak or can it be that this vehicle does a lot of short driving in cold and humid Canadian weather?
    I also took advantage of the sump being off and removed the crank sensor for an inspection. The sensor was clean and undamaged, however upon my attempt to remove it, I noticed that the two bolts that hold it in place were both loose. Could this be the cause of my lack of power, high fuel consumption and high calculated load readings?
    Thank you guys for givng me so much help. I hope that I can recipricate in turn.
    Kevin.
    P.S. I have eliminated the possibility of fuel injectors. I removed them and had them ultrasonically cleaned and tested. I testede fuel pressure and it read 37 psi. I also installed fresh Irridium plugs and 7mm Silicone NGK plugwires. I tested the four coils ressistance and they were all the same and working. Crankcase ventilation is clean on both banks and the purge valve holds vaccum with the engine off and pulsates with the engine running. I wonder is this the correct operation for the purge valve?
    Wow. I hpe I didn't give you a headache. Sorry.

  12. #11
    JUNIOR ROVER Escape's Avatar
    Join Date
    June 4th, 2007
    Location
    Belgium
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    Re: High calculated load at Idle & High fuel consumption

    Quote Originally Posted by Kevin
    OK. Now I have removed the sump and checked it out. I turned the crank until I had all the slack on the side that I could see and between the camgear and the crankgear from what I could tell the is a 10mm to 12mm or about 1/2 inch or less slack in the chain. What is the normal amount of slack?
    10-12mm seems a lot. If you put a screwdriver or similar to the side of the chain in between both sprockers, you should barely be able to move it inwards. A new chain has so little slack, it is actually a very tight fit sliding the sprockets over the shafts.

    As for the CKP, the bolts not being very tight shouldn't be a problem (unless they fall out), as long as the sensor itself can't move about.
    4.0 SE manual, 1995, 'Piper': daily, GENIII, 4.6
    4.0 SE manual, 1997, 'Priscilla': new addition
    4.6 SE auto, 1995, 'Prue': GF daily, now 4.0
    2.5 DT manual, 1996, 'Paige': retired
    D90 TD5, 2005, 'Nessie': TR2 racer

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