Help Please - 3.0cdti

[renodci]

2005 3.0cdti Auto - 74k; serviced at 71k.

Hi all, would like some advice with a problem my car's developed today please. It drives fine at low revs but there's a massive flat spot at 2,500 revs which is very difficult to rev past, and if I put my foot hard down it hunts around the gears because the engine won't rev. It feels as if the engine is being choked when it reaches 2,500 revs (almost like hitting the rev limiter except that it will eventually struggle past that point). I've got no dashboard lights on and prior to today, the car ran absolutely fine.

Am I right in thinking that the EGR valve should open under the following 2 criteria: either at 2,500 revs; or when the engine is under load? My suspicion is that the valve is stuck and possibly needs cleaning?

Does that sound likely from the symptoms described? Is there anything else I should be looking at as well?

Thanks in anticipation

John.

[unknownbullet]

Literally sorted my out the other day with very similiar issue. Check the hoses i mean properly check the hoses on the vacumn solenoid thingy at the front of the engine bay! Check both going into the boost solenoid and the one going to the too of the engine, about 15cm away. Mine had a very slight slit on the kink of that connection, simple replace jobby and boom full boost!

Any slighty slit will grow under pressure of turbo.

[Mark The Cabby]

Hi John,

I owned a 3ltr auto for 5 years and I too had the same symptoms with my Signum and it led to the suction control valves on the high pressure fuel pump. This come under what Vauxhall call field remedy 1957 and can be diagnosed on a tech 2 by looking at fuel requested vs fuel delivered.

the valves were about £80 but it books about 6 hours labour...

i too thought it was my EGR valve and had it changed just to find out about the SCV's

[m8internet]

This sounds like the early symptoms of a blocked Suction Control Valve
Search SCV
The fuel pressure is below 50% so the turbo becomes switched off, the revs fall, the turbo is reactivated, and the process repeats
In manual gearbox the solution is to pulse the gas pedal until the revs reach 3000rpm
It often feals like the brakes are applying / pulsing, even though your foot is right down on the gas pedal
Once the fuel pressure falls below 25% (which takes about 1000 miles from first symptoms) the EML warning will come one but without any fault code (actually it just reads as Unknown Error) and the car is very difficult to get above 30mph, and in extreme cases won't even reach 2nd gear

I would suggest visiting a dealership and requesting the update to the EMS, Field Remedy 1957
This will then present a fault code confirming this issue exists
If you do not have a warranty, then buy one now
The part (containoing two SCV, as both need to be replaced) costs £150, but the labour is a massive eight hours

The EGR Valve fault will put the EML on with the engine in Safe Mode, but this is easily cleared, and on the third will go straight to the Emissions Warning Light which remains active for 48 hours
Sadly in this engine the EGR Valve cannot be cleaned, and to make it worse although you can see it takes about four hours labour to replace

[renodci]

Thanks all - very helpful replies - not what I wanted to hear though! Are there any other symptoms of blocked SCV's; and is it possible to clear the blockage (eg: driving at sustained high revs)? And is it normal that once you (eventually) manage to get the revs over 3,000 the engine pulls strongly from there up to the red line (because mine runs fine once past 3,000)?

As a side point; from what has ben described above, it sounds like the turbo only kicks in at 3,000 revs - is that correct? I always imagined it boosted from around 2,000.

All your help is greatly appreciated. I'm no good at working on engines, but I do like to try and understand how they work (or don't!).

[Celes]

It does sound like a fuelling problem. I had the same problem (not just once) and it always resulted in some fuelling issue (blocked fuel filter, bad fuel or the infamous SCVs). It usually stored a bazzilion fault codes from EGR to turbo and various fuel pressure faults. However, the fault light never came on!

Once passed the judder at max torque (which should be around 2500!) i.e. high fuel pressure, the engine will pull strongly/normally as the SCV momentarily unblock. The symptoms usually return at a later time. When there is a problem with the SCVs, even if the car runs fine-ish for the time being, you will notice some irregularities (more smoke, weird power surge)

[renodci]

Grateful thanks particularly to m8internet & celes for your help on this. Quick update; I've just taken the car to my mechanic who plugged it in and found no fault codes stored. His advice to me was to take it to Vauxhall for a full diagnostic of the problem. I must admit I'm reluctant to do that because from what I've read on here, Vauxhall themselves are not very good at diagnosing problems with th 3.0cdti. Strange thing is that after being driven extremely hard by the mechanic, the problem no longer seems to exist in 1st and second gears - still there in the higher gears though. The mechanic did suggest that it could be the gearbox speed sensor - any comments on that anybody?

The way I see it, I now have two options; pay my mechanic to change the scv's and just hope that it does indeed solve the problem, or try and take out a warranty to cover the car in the hope that the diagnostic and solution will be covered by the warranty. Can anyone recommend a good warranty?

[ScottyV6]

I would suggest the cheapest option first and change the fuel filter.

[renodci]

Lol.......I've spent the last two hours reading through other threads on here relating to fueling problems and had just come to exactly that conclusion! I've even got a spare fuel filter sitting in the garage - just need to get some diesel in a can so that I can top it up when I put the new one in. I had the filter changed only 3,000 miles ago; but it doesn't seem uncommon for the filter to get clogged very quickly. Fingers crossed that solves the problem.

[m8internet]

Thanks all - very helpful replies - not what I wanted to hear though! Are there any other symptoms of blocked SCV's; and is it possible to clear the blockage (eg: driving at sustained high revs)? And is it normal that once you (eventually) manage to get the revs over 3,000 the engine pulls strongly from there up to the red line (because mine runs fine once past 3,000)?

There are other symptoms, but these appear once the issue gets worse (and by that stage the car is pretty much undriveable)
You won't get a fault code, unless the EMS has been updated from Field Remedy 1957
I would suggest discussing this with the dealership, as it is a known issue and affects all engines eventually

Yes, once the revs have passed 2500rpm you will be able to increase power
This is much easier downhill and with very little gas
However, as soon as the fuel flow increases the fuel pressure will fall

A blocked SCV cannot be cleaned without removing the Fuel Pump, a very poor design fault with this engine