Help me diagnose my DERV misfire....

[Petrolhead_Rich]

So the Volvo decided last night it wanted to be an eco car and run on 3 cylinders, It's a diesel so that rules out spark plugs and all the stuff I understand, but how do I go about tracing this on a diesel??

I'm thinking of disconnecting the injector wires one at a time, the ones that make a difference are connected to working cylinders, the ones that make no difference are connected to faulty ones?!

Compression test is on the cards too obviously, but assuming that checks out ok would it be worth changing injectors from working to non-working cylinders, then repeating the test to find out if the injectors are working?!

based on the simplicity of diesels, no throttle etc I'm guessing it has to be fuel or compression issue right?? Glow plugs would not affect the engine when its running at temperature?

P.S. the fault started while driving, after driving for a while, with the engine at temperature, driving at motorway speeds if that helps??!!

[300bhp/ton]

What type of diesel is it? As in how old. Tdi would need to be diagnosed different to a crd.

The only time I had an issue was on a Pug 106. The fuel line had cracked. It wasn't leaking fuel but it was sucking in air, so missed fired due to no or low fuel and would sometimes stall. Replaces the fuel line and all was fixed.

But yes on a crd it could be injectors or even ecu related. Is it throwing any warning lights? And if it's OBDII compliant it might be worth getting the ecu read to see if it's logged any error codes.

[boredofmyoldname]

Is it the 2.0 PSA motor that is shared with the Focus? If so injectors could be your issue

[Petrolhead_Rich]

2004 (Euro4 Common Rail jobby)

It throws an error, but it's been throwing errors for a few weeks and working fine.

Does anyone know if there is any free OBD software around? I have an OBD reader with the VAG-COM software, presumably the same cable with some different software would work???

[confused_buyer]

Petrolhead_Rich said:

2004 (Euro4 Common Rail jobby)

It throws an error, but it's been throwing errors for a few weeks and working fine.

Does anyone know if there is any free OBD software around? I have an OBD reader with the VAG-COM software, presumably the same cable with some different software would work???

VAG-COM will do basic OBD2 reading so you already have all you need.

[anonymous-user]

Petrolhead_Rich said:

2004 (Euro4 Common Rail jobby)

but it's been throwing errors for a few weeks and working fine.

fine?? really?? you don't think that it might have been warning you that something was up, that now has totally failed??

For a full on single cylinder misfire, if accompanied by no mech faults, it's gotta be a failed injector or injector drive. A simple Diag check will almost certainly tell you the problem in seconds.

you have 2 options:

1) spend ages and ££ randomly changing (expensive)bits till it works

or

2) Bite the bullet, and get a garage with suitable diag gear to pull the codes (make sure you get them to reset the codes first to clear all the old faults you have probably generated by driving rounds for weeks with something failing)


BTW, if you start sticking multimeters or osciloscopes on the injector wires, be a bit careful, some of them run as high as 100v, which will give you a nasty jolt for your troubles !!!

[Petrolhead_Rich]

Max_Torque said:

fine?? really?? you don't think that it might have been warning you that something was up, that now has totally failed??

For a full on single cylinder misfire, if accompanied by no mech faults, it's gotta be a failed injector or injector drive. A simple Diag check will almost certainly tell you the problem in seconds.

you have 2 options:

1) spend ages and ££ randomly changing (expensive)bits till it works

or

2) Bite the bullet, and get a garage with suitable diag gear to pull the codes (make sure you get them to reset the codes first to clear all the old faults you have probably generated by driving rounds for weeks with something failing)


BTW, if you start sticking multimeters or osciloscopes on the injector wires, be a bit careful, some of them run as high as 100v, which will give you a nasty jolt for your troubles !!!

The error was diagnosed as faulty intake/turbo control solenoids, they open the inlet flaps to allow air to bypass the inter cooler when the engine is cold and open the variable veins, these were all bypassed so the turbo is "always on" and air is always running through the inter cooler, no other errors, that was less than 4 weeks ago, no misfires only the occasional error.

Now the engine is misfiring, the "engine system service required" message has become more common.

I don't normally ignore warning lights, but I knew what was required and that it was only slightly affecting fuel economy with having the turbo open all the time so have left it until summer when I planned to do a bit of a service/overhaul.


After running my simpleton tests number 4 cylinder is not running, plan now is to swap that with number 2 injector to see what happens, compression is good across all four cylinders.

Sadly I really don't have the cash for running diagnostics at this point having spent nearly £2K four weeks ago on the bloody car to get it running!!!

[anonymous-user]

Petrolhead_Rich said:

The error was diagnosed as faulty intake/turbo control solenoids, they open the inlet flaps to allow air to bypass the inter cooler when the engine is cold and open the variable veins, these were all bypassed so the turbo is "always on" and air is always running through the inter cooler, no other errors, that was less than 4 weeks ago, no misfires only the occasional error.

Please tell me you didn't disconnect or otherwise "bodge" the turbo's vane position control system??? if you have, you might find that your turbo is also rather broken.


And, i'm pretty sure there isn't an "intercooler" bypass on any engine i've ever worked on, so what did you actually bypass?? (EGR, intake runner control??)

[Petrolhead_Rich]

Max_Torque said:

Please tell me you didn't disconnect or otherwise "bodge" the turbo's vane position control system??? if you have, you might find that your turbo is also rather broken.


And, i'm pretty sure there isn't an "intercooler" bypass on any engine i've ever worked on, so what did you actually bypass?? (EGR, intake runner control??)

Intercooler wise, there are two inlet pipes at the front of the engine, one comes up PRIOR to the intercooler and into one side of a Y pipe, with a vacuum operated butterfly valve, the other side of the Y pipe has a second butterfly valve and is connected to the other side of the intercooler:



I have "bodged" the vane position for now, by connecting the vacuum pipe to it directly to the vacuum pump, so in effect the solenoid is open, that will not break my turbo in any way, as the car does this anyway as soon as you put your foot down or are over a certain RPM threshold, the only downside is you get a small amount of boost at tickover.

Anyway, I've found the issue, cylinder #4 has little or no compression!