knocking diesel engine - Page 4

pannono · 30th July 2013, 16:36

Hi,
I have a well similar problem as mick1960.
Rover 75 cdti, saloon, automatic, 2004, 80.000 mls.
The engine is knocking, the idle is rough. The rev is bouncing up and down between 600-750.
When I put the car in D or R the whole car is shaking for a second or two and the knocking noise comes. If I put the it back to P or N the knocking disappears, but the rough idle is still there.
When I`m driving the knocking disappears above 1800-2000 rev in 1st and 2nd gear and it disappears in 3 4 5 because the speed is a bit higher even the rev is low.
When I have to brake, just before I stop -the car goes very slowly- the rev drops down to 400-500 for a second and the car is shaking but the rev goes back straight to the 600-750 rough idle.
This is always happening when the engine is hot. It is not happening with cold engine.
The performance of the car is good. No smoke, no power loss, kickdown is good.
I think Ron is right but I would located the problem first rather than start to spending my fortune on the car.
Any help appreciated.
Thank you

Roverron · 30th July 2013, 19:15

Quote:

Originally Posted by pannono

Hi,
I have a well similar problem as mick1960.
Rover 75 cdti, saloon, automatic, 2004, 80.000 mls.
The engine is knocking, the idle is rough. The rev is bouncing up and down between 600-750.
When I put the car in D or R the whole car is shaking for a second or two and the knocking noise comes. If I put the it back to P or N the knocking disappears, but the rough idle is still there.
When I`m driving the knocking disappears above 1800-2000 rev in 1st and 2nd gear and it disappears in 3 4 5 because the speed is a bit higher even the rev is low.
When I have to brake, just before I stop -the car goes very slowly- the rev drops down to 400-500 for a second and the car is shaking but the rev goes back straight to the 600-750 rough idle.
This is always happening when the engine is hot. It is not happening with cold engine.
The performance of the car is good. No smoke, no power loss, kickdown is good.
I think Ron is right but I would located the problem first rather than start to spending my fortune on the car.
Any help appreciated.
Thank you

Its a fuelling issue, either too much or not enough, which causes the knock and erratic idle. Its probably too much fuel from a leaking injector, or a maf signal that is far too high but other causes can be: fuel rail sensor out of spec, fuel pressure regulator playing up.
I'm inclined to think its an injector dribbling the sudden drop of fuel causes the knock in one cylinder and the engine tries to speed up but the idle stabilisation tries to prevent it.
To help diagnose it, disconnect each injector plug in turn and see whether this has an effect and point to the suspect injector.
Ron

pannono · 31st July 2013, 09:50

Thanks Ron,
I will try to disconnect the injectors.
Sorry but I`m not a big mechanic guy (I can do basic things) and I don`t really understand... do I need to disconnect all the 4 injectors one by one or disconnect 3 and leave in 1?
Could u give me a bit more details about the job?
What exactly need to do and how?
I forgot to mention: when I put the car in D or to R the rev suddenly drops down with the car shaking for a second or two. And the car vibrates also when I put it back to N or P with the rev drops down for a second.
What I don`t really understand why the knocking disappears in N and P, why the knocking disappears at higher speed?
Sorry for being a headache but I love this car and I wanna fix if it is not so expensive.
I will try to check the sensors. I know how to disconnect the MAF.
How can I check the rail sensor and the pressure regulator?
Thanks for your help.

Roverron · 31st July 2013, 10:06

Quote:

Originally Posted by pannono

Thanks Ron,
I will try to disconnect the injectors.
Sorry but I`m not a big mechanic guy (I can do basic things) and I don`t really understand... do I need to disconnect all the 4 injectors one by one or disconnect 3 and leave in 1?
Could u give me a bit more details about the job?
What exactly need to do and how?
I forgot to mention: when I put the car in D or to R the rev suddenly drops down with the car shaking for a second or two. And the car vibrates also when I put it back to N or P with the rev drops down for a second.
What I don`t really understand why the knocking disappears in N and P, why the knocking disappears at higher speed?
Sorry for being a headache but I love this car and I wanna fix if it is not so expensive.
I will try to check the sensors. I know how to disconnect the MAF.
How can I check the rail sensor and the pressure regulator?
Thanks for your help.

Disconnect the plug from one injector at a time - reconnect the first one, then disconnect the second and so on.

Checking the fuel rail sensor is best done by swapping from another 75 or ZT.

Are you sure the knocking is not an faulty engine mount. The lower one under the engine is prone to failing and the engine rocks too much.

Watch the engine and see if the knock occurs when it rocks a lot.

(This wouldn't be the cause of the idle speed being erratic but you might have the both (unrelated) faults.)
Ron

ProfDave · 31st July 2013, 11:32

worth checking the engine mount to me; if it is worse in D and goes in R that sounds like your knock suspect

they can be very worn! This was mine and it had a similar effect with the engine moving about making the whole thing feel really rubbish

pannono · 31st July 2013, 11:46

I don`t think it is the engine mount because the knocking comes as i put the car in D or R with my leg on the brake and the car is in standing position. And it is a permanent rattle-ish knocking noise, which is disappears as I put car in N or P.
I think in this position the engine has a very little rocking. it is only my thinking. I don`t know much about these things. But I will have a look anyway.
Thanks for the picture and the advice ProfDave.
Do I need to swap the fuel pressure regulator to an other one to check?

ProfDave · 31st July 2013, 12:11

the mount is underneath; its well worth having a look at as its very easy to change it ;

the movement of the lower part of the engine can make things knock into eachother when in driver or R

will take only a few minutes to check;

I am afraid you wll need to stick to Ron's advise on injectors and so on as mine have never done anything wrong

pannono · 31st July 2013, 12:23

I just checked,
To get access to the fuel pressure regulator we need to remove the starter unit. So I can`t do that.
The car will be checked by a fault code reader tomoro monin.
I will let u know if any code number comes up. It will I suppose.
I was thinking and there is a possibility to have both problems ( fuel and mounting)
The erratic idle and the rev drop (and knocking) from fuelling issue
The shaking or knocking from engine mount
Thanks for the help

Arctic · 31st July 2013, 12:40

Quote:

Originally Posted by pannono

I just checked,
To get access to the fuel pressure regulator we need to remove the starter unit. So I can`t do that.
The car will be checked by a fault code reader tomoro monin.
I will let u know if any code number comes up. It will I suppose.
I was thinking and there is a possibility to have both problems ( fuel and mounting)
The erratic idle and the rev drop (and knocking) from fuelling issue
The shaking or knocking from engine mount
Thanks for the help

Hi Pannona.
What milage as your car done so far if over 65000 i would take a look at the lower engine mount as suggested already just looking will not be enough you need to remove it and check it properly.

If split you need to change it either with a new OEM mount or an up rated powerflex but try and modify the centre metal insert as this is much less harsh Arctic

pannono · 31st July 2013, 12:47

Thanks Arctic,
Where is this mount located?
Is other any other lower mount or only 1?
Could u tell me how to do it and what tools do I need please?

30th July 2013, 16:36	#31
pannono Regular poster Rover 75 saloon Join Date: Jul 2013 Location: Bracknell Posts: 39 Thanks: 0 Thanked 0 Times in 0 Posts	Hi, I have a well similar problem as mick1960. Rover 75 cdti, saloon, automatic, 2004, 80.000 mls. The engine is knocking, the idle is rough. The rev is bouncing up and down between 600-750. When I put the car in D or R the whole car is shaking for a second or two and the knocking noise comes. If I put the it back to P or N the knocking disappears, but the rough idle is still there. When I`m driving the knocking disappears above 1800-2000 rev in 1st and 2nd gear and it disappears in 3 4 5 because the speed is a bit higher even the rev is low. When I have to brake, just before I stop -the car goes very slowly- the rev drops down to 400-500 for a second and the car is shaking but the rev goes back straight to the 600-750 rough idle. This is always happening when the engine is hot. It is not happening with cold engine. The performance of the car is good. No smoke, no power loss, kickdown is good. I think Ron is right but I would located the problem first rather than start to spending my fortune on the car. Any help appreciated. Thank you

31st July 2013, 09:50	#33
pannono Regular poster Rover 75 saloon Join Date: Jul 2013 Location: Bracknell Posts: 39 Thanks: 0 Thanked 0 Times in 0 Posts	Thanks Ron, I will try to disconnect the injectors. Sorry but I`m not a big mechanic guy (I can do basic things) and I don`t really understand... do I need to disconnect all the 4 injectors one by one or disconnect 3 and leave in 1? Could u give me a bit more details about the job? What exactly need to do and how? I forgot to mention: when I put the car in D or to R the rev suddenly drops down with the car shaking for a second or two. And the car vibrates also when I put it back to N or P with the rev drops down for a second. What I don`t really understand why the knocking disappears in N and P, why the knocking disappears at higher speed? Sorry for being a headache but I love this car and I wanna fix if it is not so expensive. I will try to check the sensors. I know how to disconnect the MAF. How can I check the rail sensor and the pressure regulator? Thanks for your help.

31st July 2013, 11:32	#35
ProfDave This is my second home ZTT, Contemp Saloon, Duotone Tourer Join Date: May 2012 Location: Llandeilo Posts: 4,192 Thanks: 290 Thanked 387 Times in 333 Posts	worth checking the engine mount to me; if it is worse in D and goes in R that sounds like your knock suspect they can be very worn! This was mine and it had a similar effect with the engine moving about making the whole thing feel really rubbish

31st July 2013, 11:46	#36
pannono Regular poster Rover 75 saloon Join Date: Jul 2013 Location: Bracknell Posts: 39 Thanks: 0 Thanked 0 Times in 0 Posts	I don`t think it is the engine mount because the knocking comes as i put the car in D or R with my leg on the brake and the car is in standing position. And it is a permanent rattle-ish knocking noise, which is disappears as I put car in N or P. I think in this position the engine has a very little rocking. it is only my thinking. I don`t know much about these things. But I will have a look anyway. Thanks for the picture and the advice ProfDave. Do I need to swap the fuel pressure regulator to an other one to check?

31st July 2013, 12:11	#37
ProfDave This is my second home ZTT, Contemp Saloon, Duotone Tourer Join Date: May 2012 Location: Llandeilo Posts: 4,192 Thanks: 290 Thanked 387 Times in 333 Posts	the mount is underneath; its well worth having a look at as its very easy to change it ; the movement of the lower part of the engine can make things knock into eachother when in driver or R will take only a few minutes to check; I am afraid you wll need to stick to Ron's advise on injectors and so on as mine have never done anything wrong

31st July 2013, 12:23	#38
pannono Regular poster Rover 75 saloon Join Date: Jul 2013 Location: Bracknell Posts: 39 Thanks: 0 Thanked 0 Times in 0 Posts	I just checked, To get access to the fuel pressure regulator we need to remove the starter unit. So I can`t do that. The car will be checked by a fault code reader tomoro monin. I will let u know if any code number comes up. It will I suppose. I was thinking and there is a possibility to have both problems ( fuel and mounting) The erratic idle and the rev drop (and knocking) from fuelling issue The shaking or knocking from engine mount Thanks for the help

31st July 2013, 12:47	#40
pannono Regular poster Rover 75 saloon Join Date: Jul 2013 Location: Bracknell Posts: 39 Thanks: 0 Thanked 0 Times in 0 Posts	Thanks Arctic, Where is this mount located? Is other any other lower mount or only 1? Could u tell me how to do it and what tools do I need please?