Vectra, unstable cruising speed - Cyrill666 {P}
Hello all,

My Vectra's starting to play up again. It's a 1999 2.0 Di Estate with just over 100k on the clock.

The symptoms are when in fifth gear cruising at around 75-80mph (tut-tut, I know!), around 2750 rpm it seems that the engine management system can't decided if I'm accelerating or decelerating, the net result being that the car behaves as though I'm pumping the accelerator slightly giving vehicle occupants a *very* gentle forward/backward rocking motion. It is only very, very slightly noticeable at the moment, but it's definitely there. It's more noticeable when accelerating from 70-85 ish (foot hard down).

Things I'll try next time I'm out are to see if it's also evident in other gears with a similar rpm, and see if it's evident under less harsh acceleration.

The engine management light did come on once, for a few seconds about a month ago when cruising at around 80. It went out and hasn't been seen since (fingers crossed!)

For the record, I did have turbo problems back in September:

Any ideas would be gratefully received at this point though.

Kind regards,
Vectra, unstable cruising speed - shed
its not cos the a/c compressor is cutting in and out is it?
Vectra, unstable cruising speed - Dynamic Dave
Cyril, sounds like a fly by wire throttle problem. Instead of a traditional cable, it's all done with electronics and potentiometers (variable resistor) I guess after a 100k miles with the throttle sat in the same position cruising at 70-80mph something may have worn just at that particular point on the potentiometer, thus giving erratic speed variations. Then again, I could be totally wrong!!
Vectra, unstable cruising speed - Cyrill666 {P}

It's not the A/C, it wasn't switched on tonight during the drive home.

Fly by wire sounds a likely suspect. I'm assuming these are sealed units and can't be overhauled. Does anybody have a price for replacement of the accelerator position sensor?

Thanks for your replies.

Kind regards,
Vectra, unstable cruising speed - Cyrill666 {P}
I should also point out that this particular car doesn't have cruise control.

Vectra, unstable cruising speed - RichardP
I had a very similar problem with my 2K Vectra DI where the engine management light would illuminate occasionally at about 73 to 74 MPH. It never came on at other speeds! The car also under heavy acceleration, particularly in 3rd, 4th and 5th gears used to 'surge' and I could hear the turbo whistle on and off and the car rocked as you described. A new air flow meter cured the problem on my car, which cost about £150 from Vauxhall which I fitted myself.
Vectra, unstable cruising speed - Cyrill666 {P}
Thanks Richard,

Following testing (of sorts) on a 50 mile journey, by holding the speed between 70mph and 75mph (2500rpm) in fifth gear I managed to make the engine management light illuminate three times - although it went back out again after a second or so, and there was no change in performance. The rocking or surging didn't seem too evident although the effect is currently slight, and it was fairly windy so I may have missed it. By holding the rpm at 2500 in other gears, I couldn't recreate the problem, although I couldn't do this for extended periods for obvious reasons.

When you replaced your air flow meter, did you notice any improvement in the overall performance of the car, or fuel economy? I only ask because the car seems less perky that it used to be, and the average mpg has dropped from around 49 to 46. The loss of perky performance may well be me just getting used to the car, plus it has just over 100k on the clock.

Kind regards,
Vectra, unstable cruising speed - RichardP
I had the management light issue for about a month in Feb/March last year, where it would come on at motorway speed whilst in fifth gear. At first the light came on several times over a 15 mile motorway journey, and stayed on for about 4 to 5 seconds. After about 3 weeks of it doing this, it occasionally stayed on longer, for about 10 to 15 seconds, and if I tried to accelerate, nothing happened! At this point I decided to clean the airflow sensor with alcohol, but unfortunatly even though I took great care, I must have damaged it and when I put it back in, the light was on permanently and the car was very sluggish.
After putting a new sensor in, the car did perform better than it had for the last month or so but I didn't really notice any improvement in fuel consumption. I imagine I must have got used to the gradual decline in performance and only noticed the difference when the new sensor was put in!
Vauxhall agreed to pay for the new sensor as they said there were faulty batches of airflow sensors installed in various cars. If you do change it, make sure you buy a new air filter and ensure it fits in the air box properly.
The new sensor was about £155 incl. vat, but that was the part cost only. Vauxhall had several airflow meters in stock, it seems like they sell quite a few of them! I didn't have any diagnostics carried out at the time, I think that costs about £25.
All has been fine since, but it was mentioned by a garage that a similar fault could be due to a faulty camshaft sensor.
Hope this helps

Vectra, unstable cruising speed - Pugugly {P}
Good site recommended to me via this website was the It also has a Vectra site and cheapish parts
e.g. Cammbelt 15.00 each Delaer £18.00 for a Cav. 1.8.
Vectra, unstable cruising speed - Cyrill666 {P}
Right then,

To close this thread...

I bought a new airflow sensor from these people (Very friendly people, and I saved £50 on a dealer price for a new airflow sensor (brand new, BOSCH)): {Link amended as previous one posted here is no longer working. DD - 10/06/05}

Fitted the new meter last night... took longer than the two minutes I thought it would take, as Vauxhall thought it would be funny to use screws with a torx head (but not the normal torx head, the one with the little piece of metal in the middle of the hole so standard torx bits don't fit...Grrr). Still a decent pair of pliers soon sorted that ;)

Anyhow... as soon as I pulled away in 1st gear the car had loads more power, this was evident right through the gears - I can't remember the car ever being as lively as it is now, and I've done 21k since buying it.

The car no longer does the "rocking" thing at cruising speeds, I don't see the EML light flicking on and off between 65mph and 75mph anymore and I can now happily let the engine rpm raise to the top of the turbo range without the car dropping into "limp home mode".

In short, the car is now driveable! (It's amazing what you get used to though, isn't it?)

Thanks for everyones comments and help, very much appreciated.

Kind regards,
Vectra, unstable cruising speed - Peter D
Slow/out of spec Lambda sensor response ( may be that is what your ECU light was about ), vacuum leak, may be turbo waste gate vacuum leak or pin holed Diaphragm. Regards Peter
Vectra, unstable cruising speed - henry k
>>Vauxhall thought it would
be funny to use screws with a torx head (but not
the normal torx head, the one with the little piece of
metal in the middle of the hole so standard torx bits
don't fit...Grrr). Still a decent pair of pliers soon sorted
that ;)

I know this is a bit late but
The bits to fit various security Torx bits are readily available.
I have bought two sets of so called security bits in a plastic box for just a few pounds. The kit also included flat bits with slot in them, triangular bits, hex bits with hole in the middle and many others.
I bought recently a kit in Hounslow, West London for a friend.
My kit is from a mega Tesco like supermarket in Capetown. 9 Torx and 30 other security bits in a total kit of 100 bits.
Now I am looking to use it sometime. So cheap I could not buy it.

Ask Honest John

Value my car