any ideas on why engine light comes on while idling,and will go off when driving.when light comes on it idles rough.it will start and idle fine in park.if i use handbrake at lights to hold car engine light dosn't come on, but it dose with footbrake.is it the trans.1996 2.0ltr
franc123,
Jun 6, 8:34am
Could be one of a thousand reasons being an old Vectra. You will have to get it scanned, could be a poor wiring connection or something if its doing it under those conditions. Cam and crank angle sensors were particularly bad on those things.
taion,
Jun 6, 9:14am
i believe your flux capacitor isnt getting enough gigawatts
skull,
Jun 6, 10:10am
Is it really an engine light or is it oil or alternator light?
intrade,
Jun 6, 11:15am
What is the light you talk about is it the check engine light?
check engine light? i have a fair idea what it might be from your symptoms discription a check engine light if it is on means there is a fault happening and when its off the fault is no longer there It works on correction there is a band of corection value its a old car 8 bit computer so there is 256 possible things it can be haha na that is the total processing it can do 128 is the middle of 256 so the window of correction is like 128 - + 10 so 139 or 127 if the problem moves to 140 or 127 the check engine light will turn on and go out again if the problem moves to within its -+ 10 correction value . Hope that makes sense its how the engine computer works things out and the values are what ever the engeeneers programmed the computer , i just showed you a simple example of how its programming works.on this old 8 bit computer newer cars do the same but they run less tollerance window of correction and 10 of tousends more then 8 bit processing can do.
intrade,
Jun 6, 11:38am
now to the most probable cause from the information you supply. The more accurate the problem is discribed the more easy it is to take a guess and on this old car you can guess pritty quickly what is going on its why swaptron morons could get away by guessing at things. now this is what i would check and no its not codes haha because you discribe a simple problem . its not 100% sure that i will be right with this but that is the first thing i would check.
You want to check the ground wire of your brake light , most easy thing would be to pull up a wiring diagram and look on its ground circuit of the brake light if it shares the same ground as your fuel pump. Because i think your fuelpump is earthing it self via the brake light bulbs . When you hit the brake the lights turn on and the path to ground the fuelpump used thru your lights has gone and it must now use its dodgy coroded conection whom it shares with the brake . This is why it runs rough when you press the brake because the fuelpump cant supply enough pressure while it spinns slower on a bad ground .
intrade,
Jun 6, 11:41am
as a test you could run the car and remove both brake light bulbs . the car should then run rough or even stall and not start after untill you refit the light bulbs , this would confirm it is a bad shared ground of the fuel pump.
aredwood,
Jun 6, 12:47pm
It could just as easily be a faulty connection somewhere upstream on the power side of the brake light circuit. (power to ignition coil maybe?) Load from brake lights being enough to cause some voltage drop. That in turn affects the other thing that is powered off that circuit. Also the brake lights will be wired to the ABS, cruise control, and most likely the Auto gearbox computer (which might also be the engine computer) So any 1 of these computers / systems might have a fault that is setting a trouble code.
mrfxit,
Jun 6, 7:53pm
In truth . it's the factory built in "end of life" warning light. You probably have anything from 10km's to 1000kms left before it goes BANG,
Or in most cases, simply refuse to start ;-)
intrade,
Jun 6, 9:25pm
mrfixit a simple voltage drop this even existed in older cars, just the mechanical membrane fuel pump for example was not affected by stuff like this nor was the carburettor as it shure as heck would not share a circuit of a brake light now would it? More fun is to be had when you have loads more computers and 1 computer starts to Lie due to this voltage drop to other computers the code can then be absolut non related to the problem whom caused it originally
tamarillo,
Jun 6, 9:32pm
Help my brain hurts. OP get a system scan done. It will download a fault code which will narrow it down hugely and put you on right path. I'm sensing that it's on when revs drop and you say it runs rough so maybe rough idle and low oil pressure at low revs. Or it might be something else completely so get scan.
franc123,
Jun 6, 9:42pm
Yeah nah, if it was that it would have done it 10 years ago.
intrade,
Jun 6, 9:46pm
tamarillo read what the original poster wrote and turn on your brain switch to on , it happens only when they use the foot brake , this car is a dinosaur with 8 bit computer easy as pie to work out what is wrong its brake related the code wont be what part is faulty there is no fault its a wire problem or corrosion . and for that no codes are set but wrong codes could guide you in the correct direction with code or it could actuarly misslead you when you dont listen to what the op said it only happend when they put foot on the brake.
intrade,
Jul 21, 11:28am
simple test is observe brake light for flicker and dimming . with key off do they light up i dont know possible not . then with ignition on engine off. , then with engine on and brake on what do the tail lights look like flicker dimming etc while the check engine light is turning on a assume its the check engine light or is it the brake warn light on dash? I assumed the engine light is your check engine light. Assumption is the mother of all f. ups
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