rev.s takes to long to settle after starting, using fuel alot more.

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philip pickard

philip pickard

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RR 2006 4.4 petrol jag engine. cant figure out whats wrong with this.i have no codes coming up. i changed the air intake filter. plus fuel cap. no change tested for leaks on air pipes. nothing. cleaned map sensor. havent cleaned throttle body yet but i dont think it could be that. it was driving ok last week then a light came on saying air valve well i changed AIR VACUUM SOLENOID VALVE nothing changed. so im lost!. does this model engine have a idle air valve. any idea why the rev,s stays high for 10 seconds then drops to near normal the rev,s then stay at 900 not 600.they have gone up by them selves. thanks for any good ideas
 
i have now cleaned the throttle body very carefully. engine has settled quicker now. need to give it a run. see if the fuel isnt still going down as quick. think thats done the trick.
 
no its still only doing 17 to the gallon. when it used to be over 24. talked to a RR member he thinks it could be oxygen senors not working. i asked why its not come up in a diagnostic. he did remind me that we had cleared all the old and new stuff in june. so he thinks it may not be showing up again. if i replace the 2 front sensors would this sort the fuel eating??
 
I have only worked on the BMW 4.4, I wouldn’t like to say that replacing lamba sensors would cure it.
I would expect it to throw a code quite quickly.
Can you get it on any live data and check your fuelling, throttle position and air leakage ?
 
this is just a guess but would the speed senor in the middle console under the hand brake. make the engine eat more petrol because ecu would try t compensate. then the oxygen sensor would do the same so the cycle begins... the only thing is i dont have any loss of power.. it drives just as before.. only now! the miles per gallon have dropped. i thought with speed sensors.. dont they cause power loss.just had a thught i havent changed the plugs for over 2 years. well since i owned it.so i wonder if i have a weak spark causing this problem.
DSC SPEED SENSOR SRO000010 BOSCH 0 265 005 248 #191875524358
 
Last edited:
Did you manage to find out if you have an idle control valve ?
No idea on speed sensor, mine idles higher if battery charge low or when it’s cold, temp sensor maybe ?
I still think throttle body or air leak somehow , I’m only searching google the same as you
 
hi again im still stuck.. new symptoms, when driving along at any speed its ok but when you put foot down to go faster!! the revs go up but car delayed action to catch up. even with foot to floor. car takes long time to catch up to the speed you want. would this be the throttle body.
 
maybe i havent used a clutch since 1979. i put foot down, the rev,s go up. but i have to wait till car catches up. so fuel goes in but no air i think. i dont think these engines have speed sensors. 4.4 jag 2006
 
Not sure if the two problems are linked between the idle and slipping transmission symptom.
I would do some research regarding transmission and idle speed.
Normally I would say to check the transmission fluid level and condition and change that with the filter but that is expensive if it doesn’t fix anything.
Does the diagnostics have any live data?
 
had box serviced a month ago by a good mate of mine. all they do is gear boxes. said it was top class box. ive ordered a air flow sensor so see if that does the trick. live data said little rich on fuel.
 
Is the engine getting up to correct operating temp? (Water,oil,gearbox? ) unsure of how many sensors it looks at but it will be more than 1. How does the IID say “rich”
Just starting to change sensors will get expensive very quickly.
I would suggest you start with the plugs for sure.
J
 
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