Vague question.
Discussion
My cavalier has been giving me problems for some time now, in fact it's useless (see profile), but due to a financial nightmare (degree) I'm having to sell the escort.
Basically it frequently starts rough and if it does it'll break down within five miles, less if you try a hill or get stuck in traffic.
It always had petrol on the plugs after you break down, one of my plugs has turned brown for some reason, and I'm getting a big white spark instead of a small blue one like on Mum's cavalier.
Any ideas?
I've changed the entire electrical system (bar the coil, which I'm doing next weekend), the plugs, the dizzy cap, the rotor arm, the fuel pump relay, the HT leads etc.
I've cleaned the fuel filters (can't afford new stuff), its got a decent battery on it, the ECU light never comes on, (in fact none of the warning lights do) it happens in wet or dry conditions, with the car warm or cold (but most often when it's been stood for a few days) so I'm stumped.
Vauxhal want me to give them £600 to look at the damn thing 'thoroughly'.
Help!
Basically it frequently starts rough and if it does it'll break down within five miles, less if you try a hill or get stuck in traffic.
It always had petrol on the plugs after you break down, one of my plugs has turned brown for some reason, and I'm getting a big white spark instead of a small blue one like on Mum's cavalier.
Any ideas?
I've changed the entire electrical system (bar the coil, which I'm doing next weekend), the plugs, the dizzy cap, the rotor arm, the fuel pump relay, the HT leads etc.
I've cleaned the fuel filters (can't afford new stuff), its got a decent battery on it, the ECU light never comes on, (in fact none of the warning lights do) it happens in wet or dry conditions, with the car warm or cold (but most often when it's been stood for a few days) so I'm stumped.
Vauxhal want me to give them £600 to look at the damn thing 'thoroughly'.
Help!
Yea, what engine is it? -take it theres nothing on any manufacturer specific forums anywhere..
How's the compression ratio? has it been overheating/temperature fluctuating? burning any oil?
Does it smoke if you let it idle for more than a couple of minuites?
Does it use any Water?
Can you see any random leaks or know of anything else wrong with it?
Thinking head gasket/piston slap but don't know.
Do you get a good spark? run the engine with only 3 plugs in (assuming its a 4 cylinder), and the other 1 pluged into HT lead and earthed (sitting on something metal), and can you see a spark (easiest when not in direct sunlight)
If you run the engine in the dark (pitch black preferably), with the bonnet open, can you see any electric current (blue glow/sparks type thing, particularly arround HT leads) -if you grab hold of the HT leads with the engine running do you get an electric shock? (NOT recomended technique, ESPECIALLY if you've got a dodgy heart)
Just ideas just now, dont really know for sure, dont think its fuel starvation though (it does go uphill or anywhere else flat out ok? without coughing or spluttering [well, as well as anywhere])
Failing all else, it there a local "tune-up" guy or freelance mechanic type person local you could get to have a look at it??
Pete
>> Edited by pistol pete on Sunday 23 March 21:26
How's the compression ratio? has it been overheating/temperature fluctuating? burning any oil?
Does it smoke if you let it idle for more than a couple of minuites?
Does it use any Water?
Can you see any random leaks or know of anything else wrong with it?
Thinking head gasket/piston slap but don't know.
Do you get a good spark? run the engine with only 3 plugs in (assuming its a 4 cylinder), and the other 1 pluged into HT lead and earthed (sitting on something metal), and can you see a spark (easiest when not in direct sunlight)
If you run the engine in the dark (pitch black preferably), with the bonnet open, can you see any electric current (blue glow/sparks type thing, particularly arround HT leads) -if you grab hold of the HT leads with the engine running do you get an electric shock? (NOT recomended technique, ESPECIALLY if you've got a dodgy heart)
Just ideas just now, dont really know for sure, dont think its fuel starvation though (it does go uphill or anywhere else flat out ok? without coughing or spluttering [well, as well as anywhere])
Failing all else, it there a local "tune-up" guy or freelance mechanic type person local you could get to have a look at it??
Pete
>> Edited by pistol pete on Sunday 23 March 21:26
Sorry bout the lack of info...
Engine is an 1987 2.0 multi-point injection, controlled by a multronic (I think) ECU.
The critical line I missed off my previous post is as follows;
I've tried running it on 3 cyls, does it fine. The spark is good and regular, but as I mentioned it is large and white instead of sharp and blue/violet like on Mum's car.
It just doesn't like idling. If you can hold the revs up it's fine (but coz it's an auto you can't hold the revs in traffic).
I don't know any make specific forums for cavaliers...
Engine is an 1987 2.0 multi-point injection, controlled by a multronic (I think) ECU.
The critical line I missed off my previous post is as follows;
Aside from the fact it breaks down so often it's absolutely fine. Not a single leak, uses no fluids, full, smooth power when running, no smoke out the back - ever, decent fuel consumption, no overheating, no funny noises nothing.
I've tried running it on 3 cyls, does it fine. The spark is good and regular, but as I mentioned it is large and white instead of sharp and blue/violet like on Mum's car.
It just doesn't like idling. If you can hold the revs up it's fine (but coz it's an auto you can't hold the revs in traffic).
I don't know any make specific forums for cavaliers...
Another bit I forgot to mention...
There is the occasional hiss when you take the fuel cap off, but I'd discounted it as a factor becuause the plugs were wet, which implied too much fuel, as opposed to a defecit.
The fuel return line is new, fitted by me only a few months ago. I guess that doesn't mean it isn't blocked tho.
The only other suspect bit is the 'fuel flow damper', a small thingy located next to the fuel pump at the back right of the car. It's rusted badly implying its very old. Does anyone know what it does, hence if it may cause engine flooding when it dies?
There is the occasional hiss when you take the fuel cap off, but I'd discounted it as a factor becuause the plugs were wet, which implied too much fuel, as opposed to a defecit.
The fuel return line is new, fitted by me only a few months ago. I guess that doesn't mean it isn't blocked tho.
The only other suspect bit is the 'fuel flow damper', a small thingy located next to the fuel pump at the back right of the car. It's rusted badly implying its very old. Does anyone know what it does, hence if it may cause engine flooding when it dies?
Sure it's petrol on the plugs and not oil? Oil fouling the plugs due to either worn valve guides or knackered stem seals can cause this type of thing. Clues would be blue smoke from exhaust when you rev it (although you say you don't have that) and the fact the engine gets through more oil than it should. Still possible you might have enough of a leak to foul plugs at low revs without producing huge amount of smoke.
It may have the wrong coil, or the coil LT side is wired backwards? If it needs a 12V coil and you have a 6/8V ballasted coil, you'd get a fatter spark, right up to the point where the coil overheated and went open-circuit, either intermittently or permanently (intermittently would explain your 5-mile problem).
If the LT side is wired in reverse, the sparks jump the wrong way and this can cause the plugs to foul.
Regards Ian
If the LT side is wired in reverse, the sparks jump the wrong way and this can cause the plugs to foul.
Regards Ian
Are you checking the plug to an earth point (such as the block) or looking at the gap ? If your getting a white spark looking at the plug, try it against the block and see what happens. If this gives a more normal spark, clean the plugs, check the gap and clean the HT lead contacts. Have you checked all the plugs ? Or only the one that's fouled ?
Its definately petrol on the plugs, and the coil has been in there for over a year (35K miles) so it's not the wrong one. The car has only once needed an oil top-up (though that was recently) 
I like the point about the coil going 'open circuit' when it overheats, could we have a bit more detail on that please?
I like the point about the coil going 'open circuit' when it overheats, could we have a bit more detail on that please?
Disconnect the Iscv (idle speed control valve) and see if the engine speed changes.
If nothings happening when its disconnected and it dosent correct the idle speed when reconnected, that would indicate either the valve itself is faulty or possibly the internal ecu grounding is open circuit.
Have you checked for air leaks on the rubber induction pipes, they can split anywhere and cause all sorts of problems.
Easy way to test for air leaks is to run the engine and spray carb cleaner on all the intake paths, such as vac hoses and gaskets.
If theres an air leak the revs will rise and then drop back down.
Let me know if theres any thing else you find, it may help diagnose it more accurately.
>> Edited by Deltaf on Tuesday 25th March 21:05
If nothings happening when its disconnected and it dosent correct the idle speed when reconnected, that would indicate either the valve itself is faulty or possibly the internal ecu grounding is open circuit.
Have you checked for air leaks on the rubber induction pipes, they can split anywhere and cause all sorts of problems.
Easy way to test for air leaks is to run the engine and spray carb cleaner on all the intake paths, such as vac hoses and gaskets.
If theres an air leak the revs will rise and then drop back down.
Let me know if theres any thing else you find, it may help diagnose it more accurately.
>> Edited by Deltaf on Tuesday 25th March 21:05
Deltaf,
I have checked all the rubber pipes, they're secure and not blocked.
I'm very interested by your other suggestions, particularly this 'idle speed control valve', as the problem only ever occurs at or near idle.
I'll dig out the haynes manual and have a go at it this weekend.
Thanks for the input guys, I'll post again when I've had time to put some of this into practice.
I have checked all the rubber pipes, they're secure and not blocked.
I'm very interested by your other suggestions, particularly this 'idle speed control valve', as the problem only ever occurs at or near idle.
I'll dig out the haynes manual and have a go at it this weekend.
Thanks for the input guys, I'll post again when I've had time to put some of this into practice.
A thought, what is the idle speed when it dies, I had a 2.0 Cavalier (next shape) and it didn't warm idle very well, tried to idle to slowly... the next owner of the car avoided the problem by just winding the screw that holds the throttle slightly open at idle, basically holding the throttle slightly open, worth noting the car was trying to idle at around 350-400 rpm should of been nearer 600 from memory if not more (all indicated), still well below cold idle, and so fine on an auto.
When it idles properly it aims at 500, but it's pretty steady. I thought about doing something to hold it higher but if it's not at very low revs the car won't engage gear, so that idea fell by the wayside.
I suppose I could try and inch it back up and see what point it refuses to work. IIRC it should be 750-900 rpm.
I'd rather fix it properly than bodge something though as I'll be using the car for business occasioanlly and I'd hate it to die at the wrong time!
Handy suggestion though, and could work well in conjunction with what deltaf was saying.
Hopefully I can give it a go on Sunday.
I suppose I could try and inch it back up and see what point it refuses to work. IIRC it should be 750-900 rpm.
I'd rather fix it properly than bodge something though as I'll be using the car for business occasioanlly and I'd hate it to die at the wrong time!
Handy suggestion though, and could work well in conjunction with what deltaf was saying.
Hopefully I can give it a go on Sunday.
mrsd said: Are you checking the plug to an earth point (such as the block) or looking at the gap ? If your getting a white spark looking at the plug, try it against the block and see what happens. If this gives a more normal spark, clean the plugs, check the gap and clean the HT lead contacts. Have you checked all the plugs ? Or only the one that's fouled ?
Was checking the spark against a cleaned off area of the block.
I've only checked the one plug (it wasn't the one that was foulded) as they're all pretty new and all the contact points in the dizzy cap have the same wear on them.
I couldn't pursuade my mate to help me check any more as he (rather foolishly) took the plug off the engine block before I'd stopped turning the car over.
Bzzzzzz.......
Ho Ho Ho ! Aint nature wonderful?
Brought a big fat smile to me mush that has!
Just another thought mate, the Idle control valves tend to get filthy due to oil vapours and carbon build ups, it can cause em to stick.
If yer a bit handy withe the spanners, remove it and clean it out with carb cleaner, also do the throttle butterfly, ya can use an old toothbrush for that.
Dont reuse the brush tho, or your teeth will go black..LOL
Brought a big fat smile to me mush that has!
Just another thought mate, the Idle control valves tend to get filthy due to oil vapours and carbon build ups, it can cause em to stick.
If yer a bit handy withe the spanners, remove it and clean it out with carb cleaner, also do the throttle butterfly, ya can use an old toothbrush for that.
Dont reuse the brush tho, or your teeth will go black..LOL
Hmm, a search in both the haynes manual and the engine bay have failed to locate an idle speed control valve, unless you mean the one linked to the inlet manifold by two 1/2 inch air pipes?
That looks like a sealed unit so I can't clean it. I can easily see how it could be clogged as one of the air hoses failed a while back. Could have no end of junk in there.
I've adjusted the idle speed (not very well). It now idles at 1300rpm when cold, and 900rpm at the lights in drive. It hasn't died yet, but as it's an intermittent fault that doesn't mean it's fixed.
Selects gear a lot faster tho...
That looks like a sealed unit so I can't clean it. I can easily see how it could be clogged as one of the air hoses failed a while back. Could have no end of junk in there.
I've adjusted the idle speed (not very well). It now idles at 1300rpm when cold, and 900rpm at the lights in drive. It hasn't died yet, but as it's an intermittent fault that doesn't mean it's fixed.
Selects gear a lot faster tho...
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