1999 Astra revs problem

[Tasman]

1.8i 16v Astra T/1999

I've had this problem for a year or so now; around 75% of the time I dip the clutch to slow to a junction or down-shift, the revs drop quickly down to ~500 revs and then yoyos as it over/under compensates between 500 - 1100 for one or two cycles before settling at the normal idle speed. It generally happens in most conditions particularly when warmed. It tends not to do it when the a/c is on - presumably because the EMS picks the revs up to compensate.

It has caused the car to stall once or twice recently hence I would like to get it sorted now, but would appreciate some input so I'm at least I'm only semi-clueless when I take it to the dealership.

Any ideas what the cause might be?

[MORELLO]

I too have a 1999 1.8i 16v Astra, and it causes me endless problems. The engine management light is rarely off these days! I also had exactly the problem you are describing last year. I took it to the main dealers thinking only they would have the required equipment to diagnose the problem. Wrong. They informed me l needed a cam-shaft sensor - �158 + VAT, and a new throttle box - �278 + VAT (!!) At their mercy and at having paid the diagnostic fee - �30, I reluctantly had the work done. Unfortunately, and just outside their poxy 12mth g'tee period, the problem has returned, if not quite so bad. I have since had other problems such as the O2 sensor packing in. This was diagnosed by a small independant garage who was recommended to me, and who incidently told me that throttle boxes rarely, if ever need changing? This garage has the Police contract in this area so must be doing something right. I now take it to them for my diagnostic needs and repairs. So my friend, my advice would be to seek a similar garage and expect a bill of �100 up at least. Stay away from the dealerships - they use scare tactics and charge way too much for problems that shouldn't arise on a 4-5 year old car...