Help - Cavalier electrics | The Back Room Archive | Back Room Forum

What is life like with your car? Let us know and win £500 in John Lewis vouchers | No thanks

Mon 23 Apr 2001 07:46

Help - Cavalier electrics - Dave Yates

I have a 95M 2.0 20valve Cavalier which, for the past year, has been giving sensor problems - two crankshaft sensor replacements, one idle control valve replaced and a camshaft sensor replaced. Now the crankshaft sensor has gone again. The Nottingham Vauxhall dealer I've been using thinks that when these Cavaliers get 4-5 years old they show this problem and they think it's due to the way the sensor pick-ups or cabling are routed. There seems to be some sort of electrical spiking that disturbs the sensors. Their only solution is to replace the loom (apparently the newer looms have different routing or pick-ups) and they think this may sort the problem. However, by their own admission the cost of this is substantial (in excess of £500) and hardly seems warranted for a car worth about £1500 which I was intending to change.

I know this topic has been touched on before in Back-room but suspect that knowledge may have updated - does anyone have a better idea what it is that's going wrong and a cheaper way of fixing it? Does Vauxhall have any answers? One might have thought they'd have sussed it since I think it's a fairly common range of faults.

Reply | Report as offensive | Link

Mon 23 Apr 2001 07:54

Re: Help - Cavalier electrics - Andrew Hamilton

If this is electromagnetic pickup could you wrap earthing braid around exposed parts of the cable? If spikes are transmitted down the cable perhaps suppressor components as used in phone sockets might help. These short out high volts by breaking down. Alternatively use of zener diodes to reduce overvoltage at the connector could work.

Reply | Report as offensive | Link

Mon 23 Apr 2001 08:33

Re: Help - Cavalier electrics - Dave Yates

Andrew

Thanks for that - I also wondered if it's some sort of insulation breakdown that could be protected against. I'm currently talking to a specialist diagnostic outfit but any further comments, suggestions, information would be appreciated

Reply | Report as offensive | Link

Mon 23 Apr 2001 22:51

Re: Help - Cavalier electrics - D J Woollard

Dave,
You don't say what happens when these sensors "go". If it is a no start condition due to signal pickup from a failed cable screen you can try to make up your own screening. Also consider where the spurious signals are coming from, a worn starter motor can generate enough spikes to cause no-start on a poorly routed/screened crank sensor lead. If it is in-running problems consider a worn alternator could be doing the same.

David

Reply | Report as offensive | Link

Wed 25 Apr 2001 13:58

Re: Help - Cavalier electrics - Dave Yates

David

Thanks! The problem is usually shortly after pulling away (often at road junctions!) when engine is relatively cold and suddenly seems to stop and cuts out - this is almost violent. However it's also a problem in normal running usually about 2000rpm with light throttle adjustments - you can feel a jerk or a surge and the light comes on but no further problems and this often happens only once in a journey. However it does sem to get worse as time goes on and may also cause poor running when accelarating hard at 3000rpm plus.

At present it's with a specialist firm in Nottingham who reckon they've checked everything as far as they can and can only come up with a cam-shaft sensor failure (Vauxhall main dealer reckoned it was a crankshaft sensor about a week after replacing the cam-shaft sensor!). Specialist have traced loom as far as they can and all seems OK - they wonder about a dodgy batch of sensors.
It's going back to Vauxhall dealer tomorrow to check sensors and replace.
Dave

Andrew

thanks for your reply - the specialist guys reckon that the ECU seems OK but I take your point about these Cavaliers - I've heard the same thing but loom replacement seems over-the-top. I'd have thought modern electronics might have been able to determine something a bit more specific!
Dave

Reply | Report as offensive | Link

Tue 24 Apr 2001 06:40

Re: Help - Cavalier electrics - Andrew Moorey (Tune-Up Ltd.)

I would have thought that spikes would corrupt the signal at the ECU rather than destroying the Sensors. I know from experience that the sensors are a known trouble spot and the ECOTEC engine fitted to the last of the Cavs seems to be more troublesome than the Vectras. I think a second opinion on the serviceability of the sensor mightn't be a bad idea before changing it again?

Reply | Report as offensive | Link

Ask Honest John

Sell Your Car

Real MPG

Fuel Calculator