24 replies to this topic

[sdixon]

I have a nearly new VX220T with 2500 miles and I seem to have suffered a loss of power above 3000rpm. It feels like a loss of turbo boost. Two dealers have done a diagnostic test on the car but insist that there is nothing wrong. They have test driven it and say that it feels OK, which is crap. Basically they are having me on. Has anyone else experienced a similiar problem with loss of mid to top end performance? Any suggestions would be appreciated.

[turboman]

This really is normal, you will find that it will go away as you get more miles on the car. Or, if you are keeping the car outside, you have a little water/condensation in your DIS pack (distributor), which has this effect (feels like turbo lag), if your dealer takes it of (simple job) they can check this for you. Wayne

[KCVXT]

Does it feel gutless just after 3,000 until about 4,000 rpm...almost like you've suddenly hit a strong headwind...then pick up again just after 4,000rpm? Mine was doing that badly about 2,500 miles. Things have improved now I'm on 4,500 miles, and Optimax seemed to help also, although it's not completely cured the problem.

[sdixon]

The problem is not so much turbo lag, as a complete lack of punch above 2500-3000rpm. It feels like the turbo just begins to cut in and then it runs out of breath after which the acceleration is flat. It is particularly noticeable in the higher gears where there is no torque. Could it be a wastegate problem - either sticking open or opening too early? Is there an electronic sensor on the wastegate that could be faulty? I've tried the Optimax petrol and that has made no difference. The car was fine when I first picked it up but something happened after about 200 miles of normal use and it hasn't been the same since.

[goofballs]

It happens to me on and off. It happened quite badly yesterday. On other days, it doesn't have any problem. It feels like a flatspot, however yesterday, it felt like the turbo was stalling. Someone who knows about these turbo designs may know further. Does anyone know whether the Astra Gsi has similar problems. After a hard drive it goes, I have had a few over revving moments where it revs wildly when I change gear. I have switched the engine on and off and allowed the ECU to reset, and all has been well. I may try this next time when I have the flatspot problem. cheers

[richclem]

When I traded my Astra Coupe Turbo in for my VXT, one of the things that the dealer looked for in the test drive of my car ,was lack of power above 4000rpm. He said this was a known problem on some early Turbo Coupes, and may be due to a problem with the turbine blade.

[KCVXT]

I owned a 2002 Astra Turbo before the VXT and the power delivery was pretty linear right up to the limit. If anything the VXT has more power over 4,500rpm (whereas the Astra didn't really step up), and a flat area between 3-4000 rpm (which I never noticed in the Astra)!

[exjagman]

I've just changed from a 4000 mile VXT to a 1500 mile VXT. I have a definate flat spot between 3000 & 4000 rpm which is most noticeable on moderate acceleration. It's not quite so bad if you floor it. Hopefully mine will also improve with more miles.

[streetboy]

I remember something about over-boosting? The turbo spools up too quickly then backs off and it feels like you're loosing power. I think Stu said it was programmed in for economy or emissions or something? An AMD remap gets rid of it.

[wickywire]

Is your new car you got in silver Andrew?

[DEKKER]

Ive been worried sick. My 2700 mile VXT has developed a very noticeable flat spot between 3500 and 4000 revs. More noticeable in the cold damp weather. I thought perhaps it was begining to die (due to me unable to stop myself from flooring it) I was even to frightened to discuss it with others and stayed silent for weeks. But now I feel so much better knowing Im not alone. I think I'l have another blast tomorow. Oh yea I did mumble something about it when the VX was serviced a few weeks ago but the service guy just looked straight through me as if I was'nt there. DEKKER

[Turbo Head]

Most VXT's have a flat spot from 2500 to 3500, mine too until, I had a Courtenay pre-cat replacement pipe fitted, Iridium plugs (Denso IK16), and a PVD panel filter fitted dry. Flat spot has gone now reving more freely. Fairly cheap mods, I would recommed doing this.

[Turbo Head]

Is your new car you got in silver Andrew?

No he sold his sole to the devil and traded his beautiful silver vx for the red tarts car from footballers wives. A celebrity VX but the footballers wife didn't come with it!

[easy]

I have a flat spot around 3500 rpm (500 miles) I'm hoping when I get it moded things will change

[waverunner]

Within a couple of days of trading in my NA and picking up my ex-demo VXT I joined in the fun at the VX day at Bruntingthorpe last September. On my first hot lap going through the twisty bit before the main straight I experienced the flat spot. It was so noticeable that I thought the engine had died. My reaction was to floor the throttle to get the engine to pick up which it did with a vengence causing me to loose control and part company with the black stuff and go grass cutting instead. After that I posted a poll here and the results showed that about 2/3rds of VXT owners had flat spots of varying degrees. Anyone who had had a remap found the problem to have disappeared. Wayne (Turboman) found with his demo VXT that water was collecting in the DIS pack on the top of the engine and that drying this out seemed to relieve the problem. Of course, as soon as it rains water collects again and the problem seems to return which could to some degree explain the inconsistency between different VXTs, and also inconsistency with the same car on different days and weather conditions. But then why would a remap solve it? I'm certainly no expert but it seems logical that it's the ECU but I don't know why. Maybe AmD or one of the other companies offering remaps could explain more by comparing the standard mapping with the remap and see what's going on. I must admit to being very curious. As for my VXT, it had some 2,500 miles on it when I bought it and I'm now close to 9,000, and in that time I have used Optimax 95% of the time. The problem hasn't gone away but it's certainly heaps better. Whether that's the reason for the noticeable improvement or whether its just coincidence - Well, the jury is still out on that one.

[garyk220]

After a hard drive it goes, I have had a few over revving moments where it revs wildly when I change gear. I have switched the engine on and off and allowed the ECU to reset, and all has been well. I may try this next time when I have the flatspot problem.

I had this last summer. It feels like you are doing a full throttle gear change, without the electronic trickery to stop the engine over-revving. The diagnostics showed a fault with the clutch switch, which was replaced and solved the problem.

It has happened a coupe of times in the last few months. I fiddled around with the clutch switch, checked the contacts, etc. and the problem went away. These switches are notorious for failing/causing problems on other cars apparently.

The first time it happened, the management light did not come on. You could only tell there was a problem by driving it. More recently, the management light came on. It went out immediately after pratting about with the clutch switch, and has not come on again since.


As for the lack of power above 4000 rpm, it could be a faulty AMM (Air mass meter). A failure can result in the engine running lean at higher revs, which may account for the symptoms in the first post. I've not had this problem, but bought a spare one, just in case - £118 at your friendly local Vauxhall dealer

Before modifying it, my car had a very small flat spot around 3000rpm, which I assumed was to do with emissions or drive by noise regs. Derestricting the airbox and fitting a Courtenay panel filter reduced this, and the AMD Stage 2 has replaced it with a huge dollop of torque

[Thorney]

As has been said above the flatspot is to do with emissions. EU regs test these at a % of max revs which is around 3400-3800rpm. Fueling is dropped momentarily to make sure the car passes. On some cars it is quite noticeable and some some not at all. Those of us here who ride bikes can testify that on some sportsbikes it's like hitting a brick wall it's so violent. (My old 1998 R1 was like this). When the ECU is reamapped (any tuner does this) they simply up the fueling at this range to maximise power rather than emissions cos they don't have to abide by any law (other than MOT and it makes no difference to that) so the flatspot is gone.

[waverunner]

That makes sense. cheers

[sdixon]

Thanks guys for all the useful comments. I'm having it looked at by a performance/tuning specialist with a rolling road so at least I'll have a few suggestions to throw at him. However, most of the comments refer to a "flat spot" between 2500 and 4000rpm whereas my problem seems to be slightly different in that it lacks power all the way up to the red line. It just seems to run out of breath. Low down torque seems fine but just when the turbo should be kicking in and doing its thing, it flattens out and feels like a normally aspirated engine. The problem wasn't there when I first drove the car - it suddenly happened. I now notice the lack of grunt, particularly in top gear at motorway speeds when full throttle produces "normal car" acceleration at best. In the lower gears when I first had it I could understand the need for the upchange light on the rev counter, but now its almost a yawn watching the needle creep round to the red line - a bit of an exaggeration, but you get the point and that's how it feels in comparison to what it was like. A mystery.

[Bengie]

Those symptoms do point to a failing AMM which is not unknown on the Turbo.