Vectra intermittent ECU fault light -
Are there any Vauxhall experts out there who can perhaps advise me. My high mileage 96p 2.0SRI has an intermittent fault with either the ECU or one of the transducers.
The problem initially started some eight months ago as an intermittent failure to idle which was sometimes accompanied by the ECU warning light. The engine would usually restart without problem. In June the problem reoccured and a trip to a local vauxhall dealer for a diagnostic readout indicated Airflow meter problems. A suggestion was also made that the idle valve was probably sticking. I cleaned the idle valve and removed the airflow meter thinking it was of the mechanical pattern and probably had a worn potentiometer track - only to find it is a hotwire device.
On reassembly all was well and the car ran without any problem for several months until a few weeks ago when the ecu light started to light up usually 2miles or so into a journey. The engine no longer stalls and after an initial hesitation which is the precursor to the light appearing then appears to run quite well. Switching the ignition off and dipping the clutch and then restarting will often clear the light which may then stay off for the remainder of the journey. My question is does the airflow meter have a reputation for intermittent problems of this nature. I suppose the problem could be something simple like a bad electrical connection or indeed may be nothing to do with the airflow indication of a few months ago. However before I start further investigations has anyone any information which may be helpful?
Re: Vectra intermittent ECU fault light -
You paid 96p for a Vectra? You was done.
Vauxhalls have a bit of a reputation for dodgy multipin connectors. Little cracks in the insulation let in moisture and all sorts of intermittent faults result. Many an ECU has bee replaced when all that was really at fault was the connector.
Try drying it out with a hairdryer, reconnecting, getting everything nice and warm, then coating with a waterproof silicone spray.
Another thing to consider is the knock sensor, If a couple of pins become dirty they can trigger the Engine management light when u take the car to higher revs. Sometimes dropping your speed and going in a higher gear clears this as well, a similar thing to turning the car off and restarting.
Re: Vectra intermittent ECU fault light -
I think David is right. The symptoms of the Vectra engine hesitating momentarily and lighting the Engine Warning light a couple of miles into a run are almost certainly the camshaft sensor.
I've come across 3 cars that behaved exactly the same way - two of them 96P SRi models. The dealer diagnosed it on both of them from the description of the fault - in neither case had the ECU memory held the fault. It seems common from about 50k miles.
As you say stopping and restarting the engine put the light back out. If the light has been on for only a short while this apparently doesn't always lock a fault code in the memory. We were told you may have to drive for at least half an hour with the light on to lock the fault into the memory.
Only problem with that is that I found the engine was operating on some sort of back-up programme, and wouldn't go over 4000 revs!
Before going too much further you should have any fault codes extracted from the ECU memory. These MAY point you in the right direction, but as you have been removing certain connections you may have introduced misleading codes yourself. Get the code memory cleared than use the car until the warning light comes on again, then re-check codes. Remember that a code that says, for instance, "airflow meter" does not mean that the component is faulty, merely that there is a fault on that circuit - could be the component or associated wiring etc. Equally, lots of faults don't flag a code.
I agree with John Slaughter about the sensor diagnosis. The early Vectras & the later Cavaliers suffered from this. Both crank & camshaft sensors went regularly on a Cavalier I had. I also had the idle valve cleaned & finally replaced. At some point ( about 5 years old with Cavaliers apparently) they seem to become overly sensitive to something - Vauxhall dealer said electrical spiking due to loom problems and suggested £500+ to fit a new loom, a suggestion I declined.
Just a hunch but after having the battery flattened trying to start after one of its peridic dos I charged it overnight and found the sensor problem seemed to have disappeared - it recurred again but made me wonder if a failing battery might somehow sensitise the thing.