2.0 dti cutting out immediately after starting

[Boz657]

Wasn't sure how best to title this thread as it's gonna be a long one with lots of info so please bear with me...

Picked up a 54 plate Signm 2.0 dti elegance at the start of the month. Very impressed with the spec for the price. Wasn't too impressed with the performance but, as mentioned on here many times, 100BHP isn't a lot for what is quite a big and heavy car so thought I'd learn to live with it.
It seemed to pull ok once you hit 2k revs so thought 'it's because its a diesel...'. However, I didn't just have to be heavy footed with it, for anything like decent performance, it was pedal to to floor, literally.

Then I started to notice it was quite thirsty, especially after reading that this was a fairly economical engine. 30-35 mpg although the trip computer was saying 45-50? Trying to drive more economically (read, slowly, very slowly) didn't change this to any degree so went back to the 'no throttle/full throttle' style I had adopted and started to read on here for ways to improve mpg and performance. Pencilled in air box mod, K&N filter and cleaning the EGR valve and poss boost sensor & MAF sensor as things I'd be able to do (when I had time....)

I had a couple of long drives planed (leeds-newcastle and back, then leeds-portsmouth and back in a week), so bought some millars, couple of shots of this in the tank and by the time I was in Portsmouth, it did seem a little bit quicker below 2k revs buy only a little, it could easily have been wishful thinking.

Got back to Leeds and had an early start the next day, it was a cold morning and it wouldn't start! Well, it took 5 attempts and it started. Seemed a bit slower on the drive in to work but was fine in all other regards. No engine warning lights or anything.
Went to get some lunch in the car and it would not start at all. It would turn over fine, the engine would fire up and cut out immediately. Try again, engine starts then dies.

So I called the AA. Chap ruled out a fuel problem straight away (can't remember why though, lol), this was my main worry due to the cost of fuel pump etc and the engine did seem starved of something. So the AA chap checks the air intakes. This is where it gets interesting...

The butterfly valve on the throttle body (i think it's the throttle body...it's directly above the EGR valve) was shutting as soon as the engine fired up. This butterfly valve is vacuum operated and the vacuum would kick in as soon as the engine fired up, shutting the butterfly valve and killing the engine (apparently this is how the engine turns itself off, makes sense...).
The AA bloke disconnected the vacuum, engine fired up fine and revved fine, really well in fact. Connect the vac pipe, same thing, it died. The vac pipe lead to a vacuum valve (directly above the radiator, on the right hand side when looking in the engine, there are two of them side by side), the AA man carefully 'tapped' it, reconnected and engine fired up fine. The 'tap' had obvioulsy released the stuck valve.

When I went to finally get some lunch (I was starving by this point!) I had to double check I'd gotten into the right car! It was pulling like the 1.9TDI company Golf I drive occasionaly! And this wasn't even going past half throttle!

Clearly, the air intake has been restricted the whole time I've had the car.

Haven't drove it enough to see if the mpg is any better but the readings on the trip computer have dropped dramatically, the current reading is staying between 30-40 mpg which is where the actual mpg was before. It used to read in the high 40's +.

So, as I was on day 28 of my 30 day warranty from the car people (I know, car supermarket and all that, just didn't have the time to hunt down a decent private sale), I've called them so they can replace the stuck vacuum valve. However, as there are some very knowledgable people on here, I wanted to run this past everyone, incase it is another component that needs replacing or is causing the issue. As the car now seems to be starting fine and running better then ever, I can see the car peoples engineers spending all of five milliseconds on this, I'll be lucky if they actually replace the vacuum valve!

Thank you to anyone who has actually read this far. Lots of info, i know....

[Boz657]

Forgot to mention, the AA bloke checked the ECU and there were no fault codes stored, in case you were about to ask,....

[James24]

I'd try to get the place you got the car from to buy you a replacement vacuum unit as you don't know if the 'tap' fixed it permanently or if will stick again.

I'm sure they'll claim that the car wasn't exhibiting this fault when they sold the car (they didn't see it themselves and you didn't point it out at the time of the sale) and so refuse to pay for it.

If that's the case and they refuse to budge, I'd get one from a dealer and fit it myself - for peace of mind as much as anything else. Alternatively, try a few scrapyards and see if you can get a decent vacuum unit for a good price.

Note that here are 2 vacuum units next to each other on some Vectras (on others one of them is behind the air filter box) so make sure you get the right one.

[Boz657]

Thanks for the quick reply!

I don't think I'll have too much resistance to them swapping the vacuum valve - they've ordered the part anyway. I just wanted to see if people recognised this problem and if there was maybe an underlying cause - or if it simply is a stuck valve on the vacuum unit.
Could the air intake have been partially closed the whole time I've had the car? This would explain the poor performance and sudden increase in performance. Would this affect the mpg?

[James24]

Thanks for the quick reply!

I don't think I'll have too much resistance to them swapping the vacuum valve - they've ordered the part anyway. I just wanted to see if people recognised this problem and if there was maybe an underlying cause - or if it simply is a stuck valve on the vacuum unit.
Could the air intake have been partially closed the whole time I've had the car? This would explain the poor performance and sudden increase in performance. Would this affect the mpg?

I don't think this is a 'known issue' with the DTi. It sounds simply like a stuck vacuum unit. Keep an eye on it once the new unit is fitted because if you still have problems you might need to get the vacuum pump checked out. The pump does power all of the vacuum devices though, so it's unlikely to be this if all of the other vacuum units are working OK.

While you are under the bonnet, check all of the vacuum pipes and their rubber ends for holes and splits anyway - replacements are available by the metre from your dealer (this is a known issue with the DTi and causes poor performance and sometimes a warning light as well). Check the air hoses for holes/splits and loose fitting at the ends as well - another know issue that causes the same symptoms.

Finally, yes a partially closed air intake could have been like that all the time - caused by the faulty vacuum unit - and this would almost certainly have caused the car to lose performance. It would probably have affected fuel efficiency as well so keep an eye on the fuel gauge / trip computer to make sure you are getting good figures now.

I see you've already put some Millers in it, but as you say you can also clean the EGR which will help (either take it out or use some Wynns EGR3 http://www.wynns.be/product.aspx?nav...3&p=23379&l=EN) and also consider something to keep that expensive fuel pump in good condition, perhaps http://www.wynns.be/product.aspx?nav...7&p=46754&l=EN.

[Boz657]

Thank you.
This forum is positvely a goldmine of friendly advice and useful information.

[the-wizard]

it does sound as though the AA have hit the nail on the head, 2.0 dti's are a fairly good engine. from tick over gently press the throttle - keep increasing the revs slowly keep going down with the pedal and you should get a SUDDEN SNAP of power!!!!. , you wouldn't have had this before hence you thinking it was gut less. all is well praise be for mr AA..

[Boz657]

Well, Car People didn't replace the valve. The chap who had agreed this apparently left the company 24 hrs after I had spoken to him, part hadn't been ordered and when they inspected the vehicle, as it was working fine they said they'd extend the warranty by another thirty days and to see if anything occured again. Anyways...

The poor performance I had encountered initially now seems to be intermittant. I've started the car, noted that the butterfly valve remains fully open, drove round the block and it's been perfect. This can happen a few times in a row. Occasionaly, I'll start the car and the actuator that moves the butterfly, shuts slightly and on a test drive the sluggish performance is back.

I know I (or car people!) clearly need to replace the vacuum valve. I'm just interested in what this butterfly valve in the throttle body actually does?!? I've been doing my reading and it appears only petrol engines need them. I'd been told it is what switches off the engine, but it turns off fine with this disconnected.
In the following thread there was a different fault that was resolved by blanking this vacuum line off. I'd like to know what it does before I attempt to block it off

http://www.vectra-c.com/forum/showthread.php?t=89343

Also, I've scoured the Haynes manual for a reference for the vacuum valves but I can't seem to find one? There is a picture of an 'Intake switchover solenoid valve' which looks identical, in the correct position (above radiator near bonnet release catch) but where there is one in the haynes manual, I have two! Can anyone point me to the relevent section? I guess I'm being dumb but I have honestly read the relevent sections several times and can't find it mentioned.

I think this intake switchover solenoid allows more air into the manifold at higher revs. Combined with poor performance under 2k revs, it doesn't really pull much past 3.25k revs so I'm wondering if both valves have a fault or maybe the vacuum pump itself?

Thank you to anyone who can help me on this!

[James24]

Well, Car People didn't replace the valve. The chap who had agreed this apparently left the company 24 hrs after I had spoken to him, part hadn't been ordered and when they inspected the vehicle, as it was working fine they said they'd extend the warranty by another thirty days and to see if anything occured again. Anyways...

The poor performance I had encountered initially now seems to be intermittant. I've started the car, noted that the butterfly valve remains fully open, drove round the block and it's been perfect. This can happen a few times in a row. Occasionaly, I'll start the car and the actuator that moves the butterfly, shuts slightly and on a test drive the sluggish performance is back.

I know I (or car people!) clearly need to replace the vacuum valve. I'm just interested in what this butterfly valve in the throttle body actually does?!? I've been doing my reading and it appears only petrol engines need them. I'd been told it is what switches off the engine, but it turns off fine with this disconnected.
In the following thread there was a different fault that was resolved by blanking this vacuum line off. I'd like to know what it does before I attempt to block it off

http://www.vectra-c.com/forum/showthread.php?t=89343

Also, I've scoured the Haynes manual for a reference for the vacuum valves but I can't seem to find one? There is a picture of an 'Intake switchover solenoid valve' which looks identical, in the correct position (above radiator near bonnet release catch) but where there is one in the haynes manual, I have two! Can anyone point me to the relevent section? I guess I'm being dumb but I have honestly read the relevent sections several times and can't find it mentioned.

I think this intake switchover solenoid allows more air into the manifold at higher revs. Combined with poor performance under 2k revs, it doesn't really pull much past 3.25k revs so I'm wondering if both valves have a fault or maybe the vacuum pump itself?

Thank you to anyone who can help me on this!

Hi,

Had the same problem with my Signum 2.2DTI. Had cleaned out throttle body, this was OK for a while. Had it dealers for a couple of days, their TIS 2000 came up with ECU problem, new pump and ECU [£1600 ish], could not say if this would cure problem.

A quick search on the 'net', was told that the 'butterfly valve' spindle gets worn with age, spindle sticks, this causes the Throttle position sensor [TPS] to give erronous signals to the ECU. The ECU tells the vacuum actuator to move butterfly valve to correct it, and you get caught in a loop, car either stalls or you can drive through it.

The other cause can be that tracks in the TPS get worn due to driving at a constant speed and again cause a signal error to the ECU.

Anyway have today replaced throttle body [£191.00 + VAT], we'll see if this fixes it.

Some engines have one vacuum unit above the radiator and some have 2. This is because some engines have the throttle valve (on the top front of the inlet manifold) and some don't.

I cleaned and checked all 3 of the vacuum-operated values (mine has all 3) to ensure that they were all working fully. It may be worth a go to see if you can identify if any of these units are sticking or leaking or something.

This works for all 3 vacuum-operated units on the DTi - the turbo wastegate (attached to the bottom rear offside of the turbo), the manifold switchover (on the nearside of the manifold close to the vacuum pump), and the throttle valve (on the top front of the inlet manifold). The turbo one won't be causing this problem but it might be worth checking while you're at it. Just follow the vacuum hoses to find each on these units. Sometimes the turbo wastegate acutator/solenoid is behind the air box and sometimes it's next to the battery box.

For each vacuum unit in turn, remove the acutator end of the hose and suck on the end of the pipe. You should see the valve moving as you suck. Check it moves backwards and forwards smoothly from fully open to fully closed without sticking anywhere. If it doesn't, it would indicate that whatever that unit moves is not able to move freely.

Once you have sucked right to the stop, put your tongue over the end of the pipe and check that the valve doesn't creep back - it should stay exactly where it is. If it doesn't you may have a leaky unit, vacuum pipe or rubber connector. Don't get any dribble in the pipes!

[bigmac]

Mines a 2.0 Dti and mines gutless between 1k and 18k after that the turbo kicks in,thought all vectra dti's were the same