knocking from engine

[Becks]

Hi, I have a recently purchased a 2007 D5 C70. When I bought it there was a slight noise which I noticed on light throttle particularly at lower speeds, although I think I can hear it at higher speeds, but more faintly. I knew the the inner CV joints were worn, and thought this was the noise. It now has new drive shafts fitted, but the noise is still there :(

It does become a lot less when the engine is hot after a run on the motorway.

I did try recording the sound, but didn't come out very well. The noise is a light knocking noise which seems to change with engine revs, but only there on light throttle. At idle there is no noise and revving the engine with the bonnet open I can't hear it. I, also now have a service engine system message come up on the dash. There also seems to be a slight misfire, again, more so when cold, but it does feel like it's there on heavy acceleration when warm.

I have done a leak off test of injectors. They are all within Volvo's recommended limits, giving between 15-25mm in 1 minutes idling.

I've just serviced the car, using genuine volvo oil and air filters and Castrol A5/B5 oil for Volvo - no change.

I have a fuel filter (genuine) to fit, which I hope to do this weekend, although approaching this one with a little trepidation having read some posts on how hard it can be to remove and possible damage to filter housing.

I have connected my OBD reader, but this is coming up with no codes, so I guess I will need DICE to read these, which is something I'm looking at getting - just trying to work out best place to buy from.

I'm not very familiar with diesels, much more familiar with petrol V6 and V8's, so any pointers as to what this might be, or next steps in investigating welcome.

[cheshired5]

I have an injectior knock currently on number 4.
The noise is distinctive up close and very easy to spot using an automotive stethoscope or a length of garden hose.:thumbs_up:
Like you, leak test is fine and I have no codes but it's now starting on the fourth or fifth crank compared to its usual second or third and economy is down by around 8mpg.
I'll be trying a run through of Diesel Purge in the next few weeks in the hope that sorts it.

[5cilinder]

Most codereaders are crap and cant read those volvo's
With the torque app and a cheap elm adapter you should read obd engine related codes
Also a chinese dice unit is helpfull for more advanced diagnose like fuelcorrections on individual injectors
Concerning your knocking injector it could be that the previous owner refurbished that one and the internal injectorcode in the ecm doesnt equal the new injectorflow
Personally a chinese dice unit is recommended with these kind of problems it isnt expensive and saves you dealertrips you earn it back within 3 dealer codereadings also that diceunit can be sold in a few years

[Becks]

I have an injectior knock currently on number 4.
The noise is distinctive up close and very easy to spot using an automotive stethoscope or a length of garden hose.:thumbs_up:
Like you, leak test is fine and I have no codes but it's now starting on the fourth or fifth crank compared to its usual second or third and economy is down by around 8mpg.
I'll be trying a run through of Diesel Purge in the next few weeks in the hope that sorts it.

I'll be interested how the injector purge goes - might try that myself. Will you be using the liqui Moly stuff?
I did try listening with a stethoscope, and although there was a difference with two of the injectors, it was very, very mild difference and certainly not a knocking noise at idle.

[Becks]

Most codereaders are crap and cant read those volvo's
With the torque app and a cheap elm adapter you should read obd engine related codes
Also a chinese dice unit is helpfull for more advanced diagnose like fuelcorrections on individual injectors
Concerning your knocking injector it could be that the previous owner refurbished that one and the internal injectorcode in the ecm doesnt equal the new injectorflow
Personally a chinese dice unit is recommended with these kind of problems it isnt expensive and saves you dealertrips you earn it back within 3 dealer codereadings also that diceunit can be sold in a few years

My reader was able to read the engine codes, but there weren't any. I have a DICE on it's way from a fellow forum member, so will see what that says when plugged in.

I changed the fuel filter yesterday. It was pretty black - see picture below. It had a date stamp moulded in to the end of the filter of July 08 !!! I'm guessing it's been a while since it has been changed. Out of interest how dirty do the filters get at normal change intervals?

[5cilinder]

They all turn black, 2008 is produktiondate ,could be a few years on the shelf

[Becks]

Well, in terms of acceleration it's going much better since the fuel filter change. Did a 250 mile commute to work yesterday and the acceleration surprised me a few times.

No change to the knocking noise though :(