has anyone ever encountered this problem....?

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james
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Location: Watford, Herts

hello again everyone

my G starts 1st time, doesnt need throttle to get it going but just recently after about 5 minutes it starts to rev erratically on its own accord, during this time applying the accelerator has no effect. It will rev like this then return to idling and then after a short while rev again sometimes cutting out altogether.

i managed to get it to limp home from work the other evening and it backfired on the way. it seems to be worse in the evening than the morning.

I cant see anything untoward under the bonnet - any ideas?!?!

cheers,

James

prwales
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Re: has anyone ever encountered this problem....?

when you mean rev erratically do you mean revs fall then rise and fall, at a 1st guess I would say it sounds like a fuel supply issue so it could be the fuel pump, the accumulator, the fuel filter or even gunge in your tank. All of the former suggestions flowing from the common problem of corrosion on the top of the tank.

james
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Re: has anyone ever encountered this problem....?

yep - the revs rise and fall, for the mot i replaced the accumulator and some of the fuel pipes but that was early summer, i can hear the pump prime. is there an easy way to drain the tank?

prwales
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Re: has anyone ever encountered this problem....?

no easy way to drain the tank but there is a hatch in the floor of the boot which you can use to put a rope around the tank whilst you undo the tank straps and the hoses. Is it worse an issue uphill?

james
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Re: has anyone ever encountered this problem....?

not that i've noticed, it started happening last week, the tank was half full of fuel. at the weekend i took it for a long drive and it was ok but it started again monday morning

prwales
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Re: has anyone ever encountered this problem....?

you could try putting a very large dose of Redex fuel injection cleaner into the tank it may work as a short term fix. Is there obvious corrosion on the top of the tank, this is absolute proof of the problem but its not always clear as it can be inside out corrosion as well. 463's came with plastic tanks to resolve this issue. You should check the fuel flow as well, if you look in the forum in the petrol section you will find a similar problem discussed at length

http://www.gwoa.co.uk/index.php?name=Forums&file=viewtopic&t=8058

james
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Re: has anyone ever encountered this problem....?

i'll try the redex solution 1st - everything else will be v.expensive

cheers

Pistonhead
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Re: has anyone ever encountered this problem....?

Hi James,

From your description, it sounds to me that you have false air leaking into the inlet, your first time start is due to fuel enrichment during a cold start situation, as the engine warms up, this enrichment reduces; with the false air leaking into the inlet manifold, the engine is runing on a lean mixture, hence the erratic idle, back fire, etc, etc...

Check to hear for air leaks at the rubber hoses which make up the idle circuit, these run close to and the back and under side of the inlet manifold.

Carefully, spray brake and clutch cleaner near the inlet manifold on a runing engine, if there is a leak, the engine will run better. TAKE CARE, NOT TO SPRAY OVER ANY ELECTRICAL PARTS! The mixture is highly combustable.

Check to see if the hose connection towards the back end of the inlet manifold is attached on. This is the connection from the warm-up regulator to inlet manifold. Towards the Battery end. You not easily see this connection, your better feel for it. Carefully, train your hand at the back end of the inlet maifold, at the right side of the engine. If you go down far enough you will meet up to the point where the hose attaches onto. Check the rubber hose by the idle screw adjuster.

Sorry, I have not checked to see which engine type you have, the description I have just given assumes for the M110 engine, the principle are the same for M103 engine.

Cheers,

james
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Re: has anyone ever encountered this problem....?

Rakesh - it is the M110 engine, checked but there seem to be no obvious sounds of air leaks. I've added a measure of Redex fuel system cleaner to half a tank of fuel and after a repeat of the initial problem the engine appears to be running quite nicely - fingers crossed, i'll let it cool down and take it out later when there's less traffic on the road.

There is one small pipe at the rear of the manifold that kind of loops over like some sort of overflow - this has nothing attached to it.

cheers

James

Jdring
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Re: has anyone ever encountered this problem....?

A loose pipe - doesn't sound right. I'm no expert, but I seem to recall that you need a vacuum pipe from the manifold or somewhere to work the advance/retard ignition timing. I think mine is a little shortened, but still connected. Get a new one and find out where that should go....I think its to the distributor.

Pistonhead
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Re: has anyone ever encountered this problem....?

james wrote:
There is one small pipe at the rear of the manifold that kind of loops over like some sort of overflow - this has nothing attached to it.

If, it is the pipe, I am thinking of, this should be attached to the warm-up regulator, which you will find mounted on the engine block, close to the bell-housing. (Same side of inlet manifold)

Alternatively, if you can manage any pictures; this will help.

Do inspect you distributor cap and rotar arm, as well.

Cheers,

Jdring
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Re: has anyone ever encountered this problem....?

Wohoo.
50 posts and now I am a contributor !!

james
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Re: has anyone ever encountered this problem....?

plenty to be getting on with - thats my saturday gone. here's an update so far; as mentioned before it starts ok on the drive in the morning and i drive to work and park in the underground car park; in the evening upon return i start it and immediately the revs start to rise and fall, it keeps cutting out, i got a backfire and after a lot of grief i got it to limp out of the car park only to die again. i left it at work overnight this time parked outside. tonight when i left work i started it, it started first time and i drove home with no problems. i'm gonna leave it on the drive till the weekend, very frustrating.

prwales
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Re: has anyone ever encountered this problem....?

James, how old is your vehicle and does it still have the heat insulation underneath the exhaust and on the top of the fuel tank? If it does this is often the source of the problem as it holds water and starts the corrosion cycle and the older the car the more likely that this is the problem.

persevere, you will sort it

Paul