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Discussion Starter #1
I took my 4.6 HSE for an MOT it passed, but when I set off home it would not rev pass 1500rpm, so turned back to the garage to see if they could find the problem.
The garage owner claimed it was running well when he took it up the road to do a brake test (he only had a rolling road brake tester for two wheel drives).
One of the guys plugged in his machine, fault codes showed "lambda sensor bank B" going high and then low, bank A showed what looked more like a graph (up and down a little).

Two questions
1. Would a faulty sensor cause the engine to only rev to 1500rpm?

2. Which side is "bank B" UK model?

NOTE:- When he was doing emissions test he had it revving at over 3000rpm for quite a while, he called it fast tick-over!
 

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No, a faulty lambda sensor will cause it to be a bit sluggish because it's trying to guess what the mixture should be. The output of the sensors should swing between 0V and 5V but most diagnostic equipment will show you 0-1V because that's what OBDII says it should be.

Bank A is the one with number 1 cylinder, so bank B is the driver's side. They're both easy enough to get to from below.

What happens when you try to rev past 1500rpm? Is it idling smoothly? Is the throttle linkage free to move properly and are all the pipes on correctly?
 

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Discussion Starter #3
What happens when you try to rev past 1500rpm? Is it idling smoothly? Is the throttle linkage free to move properly and are all the pipes on correctly?
When driving will not go past 1500rpm, idling OK but rev in park sound like back fire, I hope he did not thrash it and damage it on the brake test!
 

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I had the same issue recently and I put in a new crank sensor and that fixed the issue. Not sure if you have the same issue but crank sensors are pretty cheap so it might be worth a try.
 

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Discussion Starter #5
I had the same issue recently and I put in a new crank sensor and that fixed the issue. Not sure if you have the same issue but crank sensors are pretty cheap so it might be worth a try.
Thanks Harger
I may give it a try! I changed the fuel filter thinking it may have sucked up a load of crap being revved while stood still on the test, but still the same, pulled and cleaned the plugs, no good!
 
R

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my 99 Thor V8 had the same mine revved to about 2000rpm full throttle in P/N and when releasing the throttle slowly i would pass a point where the engine startet to revv up slowly and when pressing the throttle again very slowly you could get it up to max rev. when asking power it would not deliver and sounds like explosions in exhaust or inlet....

and it went away by itself, so a bad sensor or kable could well be causing this. I am following this thread
 

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Discussion Starter #7
when asking power it would not deliver and sounds like explosions in exhaust or inlet....

and it went away by itself, so a bad sensor or kable could well be causing this. I am following this thread
Hi Roger B

Yes mine's doing that! But mine is a 1995 GEMS. I have ordered a crank sensor, I will let you know how it pans out.
 

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Hi

Check your cats and exhaust system. If there is a blockage you have similar symptoms. I have had a partition in the rear silencer loose that was moving around sometimes really restricting the flow.

Regards

Jos
 

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Probably a bad MAF sensor IMO

They will cause the drivability problems pointed out by the OP (hesitation and lack of revs / power)without setting a CEL.

You can usually nurse the engine up to higher RPM by gently pressing the throttle, with this problem they will also run better when cold (when in open loop)

May be a coincidence that it went bad after the MOT unless the tester or someone else in the garage substituted a bad one or one of the wires to the unit was brittle and broke (you can change a MAF in a matter of seconds)
 

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Discussion Starter #10
I've fitted a new crank sensor and one (the guy I bought them from only sent 1 but I did order 2) lambda sensor, still the same, sounds like it has a rev limiter set at 1500rpm! Not sure if I should throw more money at it by trying a new Air Mass Flow Meter or take it to a RR specialist OR get rid, it has got over a years MOT!
 

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Sorry that the sensor did not fix your issue. My 1998 RR had the same issue at 2000 rpm, but the sensor changed solved the problem. I would do some more research before making a decision. Could be a simple fix.
 

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Take it back to the garage that broke it.
 

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Discussion Starter #13
Fitted the other lambda sensor AND tested the throttle position sensor and that looked okay but still no luck! seams to be a lot of water coming out of the exhaust pipe but coolant seams fine?
 

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The earlier GEMS MAF sensors seem to respond better to cleaning than the later Bosch ones.

Can't hurt to get a can of MAF cleaner and give it a blast.

Otherwise putting it back on diagnostics and looking at the live readings might give some more information...
 

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Discussion Starter #15
Hi

Check your cats and exhaust system. If there is a blockage you have similar symptoms. I have had a partition in the rear silencer loose that was moving around sometimes really restricting the flow.

Regards

Jos
You were spot on Jos! I got a call from the Range Rover specialist garage today, he said the cats were shot, due to revving the nuts off it during the MOT.
 
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what do they do at the MOT then?? here a petrol fueled car must adapt the fuel/air regulation when going from idle to 2500rpm and stabilise when kept at that 2500 rpm. If a car is not running too fat of spooling oil through the catalysts, the should not break down when going to that test. Catalysts die from getting too hot, which happens when un burned fuel gets into the cat
 

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Sounds the same as here. From the official MoT testers manual:
[h=5]1. Raise the engine speed to around 2500 rpm or half the maximum engine speed if this is lower.
Hold this speed steady for 20 seconds to ensure that the inlet and exhaust system is properly purged. Allow the engine to return to idle and the emissions to stabilise.

a. assess the engine idle speed.

b. assess the smoke emitted from the tailpipe at idle,

c. rapidly increase the engine speed to around 2500rpm or half maximum . engine speed if this is lower and assess the smoke emitted from the tailpipe. Allow the engine to return to idle.[/h]If done properly that shouldn't damage the cats, it's no different to cruising at 60mph. If the tester didn't follow this instruction he would be liable but it still should be capable of revving that high for quite a sustained period. Think about it, 75 mph (or 80 on the speedo), is around 3,000 rpm and I did that for a constant one and a half hours a couple of weeks ago when I was driving through France. My cats are still OK.....
 

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If done properly that shouldn't damage the cats, it's no different to cruising at 60mph.
Tow major differences:
- engine load, and thus possibly fueling
- no cooling airflow around the cats
 
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the no engine load, thus possibly (I guess there should be)Overfuelling part... that is exactly what they try to see in this test, wether or not the ECU regulates the amount of fuel correctly

the no cooling air... yeah that would make some difference.... but in that minute of total testing time?

so, still, NO the MOT test should not break down your catalists if your engine(management) is OK
 

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Discussion Starter #20
the no engine load, thus possibly (I guess there should be)Overfuelling part... that is exactly what they try to see in this test, wether or not the ECU regulates the amount of fuel correctly

the no cooling air... yeah that would make some difference.... but in that minute of total testing time?
It was revving for about TEN minutes!
 
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