[Costello]

Hi all,

I have a 52 plate Vauxhall Corsa 1.7 CTDI.

It has run fine for quite some time. However just before Christmas the alternator went, which I had replaced at considerable cost (over £300).

The car was fine for a week, but I was driving along and suddenly it lost all power.

I stopped at the side of the road and the car was revving on its own at 1500 revs (pulsing) and the car management system light was showing on the dashboard (the yellow spanner). If I press the brake, the revs drop down to normal when stopped.

When I tried to drive it, I couldn't get the power over 2000 revs (revs would stop increasing - as though the ECU was stopping it), which meant the only way I could drive it was to shift the gears up until the anti-stall kicked in and forced the car to accelerate. I also can't get it up hills unless I crawl along at about 10 mph.

I took it to a specialist auto-electric centre. They thought they'd solved it after several days of checking - found some wiring that was corroded and was causing the ECU to short out (something to do with the earthing of the ECU).

They rang me and said it was fixed so I went to pick it up, but as soon as I turned the ignition the car was doing the revving on its own again. They plugged in the diagnosis kit and said there were originally two codes - one has been fixed and no longer showed, but the other one still showed up on their display (related to the ECU).

They told me that they'd driven it about 5-6 miles without any problems, and seemed to think the shorting may have damaged the ECU - but the fact it drove for so long suggests it may not be broken?

I've paid over £200 so far and it has the mechanics scratching their heads. They said they could try updating the software in case the shorting caused the files to corrupt (at additional cost). Otherwise it's going to cost me £700 to replace the ECU (again no guarantee of a fix), but the car's barely worth £600, so not really worth doing.

Has anyone experienced the same symptoms, and could suggest what the problem is, and possible the fix?

I've done some research online and the revving seems to be a common problem with Vauxhall cars, but no-one else's symptoms seem to match mine exactly, nor does there seem to be a consistent fix for it. The garage had checked the sensors around the accelerator apparently and couldn't see anything wrong (that's not to say it's not this!).

Thanks in advance for any help or advice given!

Costello

 

[g4vvq1983]

Hi there, i assume this is a diesel, does sound strange, first thing i would do is disconnect the battery for about 1/2 hour and just leave it, it will loose radio code, then try it again, i think the spanner thing means serious fault don't drive it, is that right?, on a petrol it refers to the emission system specifically. it could be going onto limp home, i assume the new alternator works ok and the ign light comes on and goes off as it should...

How does the throttle work on that, is it electronic or cable, if its cable it could have a separate idle control valve, if that goes faulty it could stick open, or if you get some kind of running fault it could try to compensate for it by revving it up to keep it from stalling, i would clear all the fault codes and see if any come back....is it a common rail system do you know?....i mean it could be blocked fuel filter, could be crank or cam sensor, common rails systems have both i believe...exhausts sometimes get blocked, i would have a look at the throttle make sure the flap opens and shuts, if its electronic that isn't always easy...but don't put you fingers in the flap without disconnecting the plug first...might injure your fingers,hope that is of some help...from Fred in Essex.

 

[Costello]

Hi Fred, thanks for your reply.

Yep, it's a diesel. Well the garage has disconnected the battery several times to investigate the issue, so I guess this didn't fix it. The spanner isn't the malfunction light, I believe it's the service vehicle light, but I'm definitely not driving it right now anyway (only to the garages).

Also yes, the alternator works fine and the ignition light comes on and off as it should.

I believe it's a cable throttle, but I'm by no means a car expert so I can't be sure. The car garage said they took the throttle apart, so I would assume there were no obvious faults to it nor any obvious problems with the sensors.

When they tried their diagnosis kit after they thought they had fixed it, they said it was the ECU code still showing, but that could mean anything, right?

I hope this gives you a bit more detail.

 

[g4vvq1983]

Well if you get someone to work the throttle up and down while you look, you will soon see if its cable or not, most of the petrol ones from the c onwards are electronic, they have a bit lump on the side of the throttle body with a plug on...

Ok on the service light, well that wont effect anything, just tells you its due for a service, there is a wire on the alternator that works the rev counter, is that working ok...might be worth taking the idle control valve off and giving it a spray with carburetor cleaner...or even take the plug off so what it does to the idle...if your talking about ECU's it probably a common rail system...it has a primary pump normally in the tank, if that doesn't work it takes ages to start it up...the secondary pump runs off the fan belt and the delivers very high pressure to the fuel rail...about 13000 pounds psi, be careful with that.....i suppose it would be a good idea to get the fuel pressure checked if you can....is there a diesel place near you you could take it, some places specialize in that...could have injector problems and all sorts...I think the way those things work is there is a MAF sensor in the air trunk, that tells the ecu how much fuel it needs and the injectors open accordingly....i cant give you any concrete tests to do i'm afraid..but hope that is of some help....Fred.

 

[Costello]

Well to help others should anyone experience the same problems, I took it back to the garage and they finally found the fault.

The issue is the ECU, which sends two 5v electrical output signals - one to the engine, and the other to the accelerator pedal. However, the accelerator signal was dipping under 5v, meaning the engine would go into limp mode as the signal wasn't strong enough.

This was causing the lack of power, and the inability for the car to accelerate.

 

[g4vvq1983]

Well that's good,i assume they fitted a new ECU, yes the 5 volt reference can disappear sometimes, usually stops the car from running at all....Fred.

 

[timothyjuniourmakond]

Hi all,

I have a 52 plate Vauxhall Corsa 1.7 CTDI.

It has run fine for quite some time. However just before Christmas the alternator went, which I had replaced at considerable cost (over £300).

The car was fine for a week, but I was driving along and suddenly it lost all power.

I stopped at the side of the road and the car was revving on its own at 1500 revs (pulsing) and the car management system light was showing on the dashboard (the yellow spanner). If I press the brake, the revs drop down to normal when stopped.

When I tried to drive it, I couldn't get the power over 2000 revs (revs would stop increasing - as though the ECU was stopping it), which meant the only way I could drive it was to shift the gears up until the anti-stall kicked in and forced the car to accelerate. I also can't get it up hills unless I crawl along at about 10 mph.

I took it to a specialist auto-electric centre. They thought they'd solved it after several days of checking - found some wiring that was corroded and was causing the ECU to short out (something to do with the earthing of the ECU).

They rang me and said it was fixed so I went to pick it up, but as soon as I turned the ignition the car was doing the revving on its own again. They plugged in the diagnosis kit and said there were originally two codes - one has been fixed and no longer showed, but the other one still showed up on their display (related to the ECU).

They told me that they'd driven it about 5-6 miles without any problems, and seemed to think the shorting may have damaged the ECU - but the fact it drove for so long suggests it may not be broken?

I've paid over £200 so far and it has the mechanics scratching their heads. They said they could try updating the software in case the shorting caused the files to corrupt (at additional cost). Otherwise it's going to cost me £700 to replace the ECU (again no guarantee of a fix), but the car's barely worth £600, so not really worth doing.

Has anyone experienced the same symptoms, and could suggest what the problem is, and possible the fix?

I've done some research online and the revving seems to be a common problem with Vauxhall cars, but no-one else's symptoms seem to match mine exactly, nor does there seem to be a consistent fix for it. The garage had checked the sensors around the accelerator apparently and couldn't see anything wrong (that's not to say it's not this!).

Thanks in advance for any help or advice given!

Costello

Hi, is your problem fixed. I'm also experiencing exactly the same problem.