Not constant revs around 3K

**Boz657** · 31st January 2011, 20:40

Bit of a strange one this, I've searched and can't find anything similar anyway!

I can't seem to maintain a constant 3000 revs? I noticed whilst warming car up the other morning. I can progressively raise the revs until about 2700/2800, then the needle shoots up to 3300, then falls back to about 2800, then up to 3300, as if I was blipping the throttle and you can hear it change in the engine. However, the pedal is completely stationary whilst it does this which is quite strange. It will continue to jump as long as I hold the pedal there. It does it when cold and when fully warmed up too. It drives smoothly when in gear and being driven about, I can eg, 3k revs in 3rd and the speed is constant. Not had any fault codes appear.

Any ideas, anything to be worried about?The car drives fine generally, well, for a dti anyway. (Signum 2.0 Dti before I forget) I'm guessing something isn't quite right and prevention is better then a cure...

Thanks!

**Boz657** · 1st February 2011, 22:04

**Update**

Looks like I spoke to soon. 400 mile round trip to reading and back today, tried to accelerate to go past someone and I got the spanner light and limp home mode. Restarting the car cleared the spanner light and limp mode, but accelerating hard in 3rd, 4th or 5th and the spanner light came on.

If I don't push the car too hard it is fine and using cruise control in 5th I got up to 85ish with no problem. I drove like this all the way back from Reading to Leeds and didn't get the light once, last mile of the M621 I put my foot down to test and got the light again.

Also, my fuel efficiency is shot to pieces, on a run like this I would expect 50 mpg minimum, averaged 38ish on this run...nearly a full tank for just over 400 miles

I'm going to check ebay for a cheap fault reader and sat I'll look at replacing the vacuum pipes (had a quick check, couldn't see any split, one was slightly worn by the plastic engine cover, taped this up with insulation tape but it made zero difference) and give the egr and 'throttle' body a clean, as these seem to be the usual suspects on a dti. Does anyone know the internal diameter of the vacuum tube and a good place to source?

2011 hasn't be good to my siggy. Front left spring cracked just after new year, left rear shock started leaking oil a couple of days later (replaced the shocks myself with bilstein B4's as everyone on here rated them, the difference in handling is night and day) and now I've got the dreaded spanner light under hard acceleration!

Engine is still all over the show if I park up and just try to rev to 3k. I'm hoping this is related and not another issue.

**lee1828** · 1st February 2011, 22:08

could be your EGR valve..

**Boz657** · 1st February 2011, 22:21

I'm def going to have a look at that and give a clean if necc. Could a dirty egr cause all 3 symptoms - spanner light, v low mpg and weird fluctuating revs?

**lee1828** · 1st February 2011, 22:25

its a possibility if the if the EGR is sooted up or is sticking, i would try that first being pretty straight forward to do..

**Boz657** · 2nd February 2011, 14:46

Found the problem - Split hose. Its the black one on LHS side of engine that goes down to the LHS of radiator/intercooler and the other end goes to a metal pipe over the engine to the turbo.
Local garage doesn't do anything similar, went to vauxhall dealer, you can't buy the pipe by itself, need a whole assembly to the tune of £142!!!
I've seen people fit coloured aftermarket ones on here, I'm sure. Anyone know of a good link to get one?
I've tried taping the split up with electrical insulating tape as a temp fix but it looks like the air has started escaping already on the short drive back from dealers to work, so this def won't last my journey home.

**lee1828** · 2nd February 2011, 14:50

Glad you have found the problem mate, can you get a pic of the pipe?

**Boz657** · 2nd February 2011, 15:19

How do I upload a pic? I've got one ready.

**Boz657** · 2nd February 2011, 15:24

I'm so glad I've found what seems to be an easy thing to resolve. It will certainly explain the spanner light and low mpg, and in my mind also explains the revs...I'm guessing air would have been escaping at around 3K causing the revs and boost to drop, which would have made the then-very-small split close and cause the revs to raise again. I've had this issue for as long as I've had the car, so hopefully I'll see my overall mpg increase slightly, average 45mpg combined which I've always thought was a touch on the low side for a 2.0 dti, I don't boot it very often.

**lee1828** · 2nd February 2011, 15:24

when the 'reply to thread' box opens, you will see a paper clip symbol at along the top row of symbols, this is attachments. Open the attachments, upload the image, when upload is complete close the attachments box. Then click on the little down arrow next to the paper clip, you will see your download, double click it to put it in your reply.
Hope that makes sense