4y Spluttering When Turning Here Off?

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tollie
High Range 2WD
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Vehicle: 99 2700 DC 4x4
Real Name: Andrew

Fri Dec 15, 2017 9:50 am

Hi Guys,

Please help!! Im at my wits end.

I have a reconditioned 4y, runs perfectly even gets good consupmtion of just below 8km per litre.

Just had the car serviced in Jozi, however..................

Whenever in the lowveld (where the car lives, its a game viewer conversion) sometimes when I turn her the motor splutters sound like it firing after the ignition is off.

Up in Jozi the car never did this once and the mechinic could not find any issue. First time I turned her off in the lowveld she started doing it again.

Cant pin point the problem please Help? Any ideas.

I think it must be related to the air pressure, as the problem only occurs in the lowveld and no mechanic I have spoken to can pin point the issue?

Thanks

Andrew

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Mud Dog
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Real Name: Andy

Fri Dec 15, 2017 1:53 pm

Called "pre-ignition". It may well be a little of two or three factors combined. Air pressure at significantly different elevations will make a small difference but what is more important is the fuel octane rating and the ignition timing. Too far advanced timing will cause it alone sometimes. Does it "ping" under strain? Is the fuel octane rating the same in both areas? The spark plug heat rating can also be a factor - are you using the recommended plugs?

The 4Y is known to be thirsty, especially in a truck, but less than 8km/lit is not what I would call decent consumption unless you're talking about city driving alone. If it is for, (or includes a fair amount of) open road driving, then my knowledge gives rise to a bit of contradiction .... running richer tends to cool a petrol motor (opposite to diesel motors) and running hot is also one of the contributors to pre-ignition. If yours is giving 8km/lit overall, then IMO it's on the richer side of normal, which should counteract pre-ignition. That said, there are still all the other factors mentioned above, so even if it's a bit rich it could still pre-ignite.
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tollie
High Range 2WD
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Real Name: Andrew

Wed Dec 20, 2017 9:31 am

Hi Mud Dog Thanks for the response.

I have been putting in an additive since no ULP is available in hoedpsruit.

infact most of the time only ULP95 is available.

Do you think this could be culprit? I was thinking to run her dry and add only ULP see if the problem dissapears.

What can I add to the ULP95? Ive read contradicting things on this forum, some say an additive is required others dont.

She only ever drives offroad in a reserve @ 40km an hour.

This 4y was completely rebuildt less than 30 000km ago and runs really smooth so really want to get to the bottom of this.

Thanks again!

tollie
High Range 2WD
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Real Name: Andrew

Wed Dec 20, 2017 9:33 am

No LRP in hoedspruit

Mars
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Wed Dec 20, 2017 12:32 pm

Running-on can be caused by a number of things. One of the most common causes in carburettor engined cars was due to the collection of carbon on the pistons causing hot spots that would facilitate the ignition of the petrol. This is more typical of high mileage engines. While the engine was rebuilt 30 000 ks ago where one would not typically expect carbon buildup on the crown of the piston this vehicle has covered most of the 30 000 ks at close to idling speeds.

My first order of business would be to take it for a "highway service" i.e. to drive it at higher speed for few kilometers to get the volume of gasses flowing and the temperatures up in the combustion chamber to burn off some of the carbon. I would also check if there is a fuel cut-off valve and check that it is working. I am not too sure on the 4Y engine but if there is and it is sticky it will allow petrol to continue flowing through even though the engine is turned off further facilitating running-on.

Then there is the very valid point the the ignition timing needs to be adapted to the lower altitudes.

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LouisZ
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Wed Dec 20, 2017 12:44 pm

On a 4y its simple.

If it runs on its only ignition timing that is wrong. Check the timing. should not be more than 6 degrees.

These days if the engine was redone and the head was done properly, ie, valve stem seals there is no need for an additive to the fuel. Reason, valve stem seals these days are made for unleaded fuel in anycase.

Just use normal unleaded 95 in the Lowveld and up here in Gauteng 93 unleaded.

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Family_Dog
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Wed Dec 20, 2017 5:42 pm

This is correct:

"These days if the engine was redone and the head was done properly, ie, valve stem seals there is no need for an additive to the fuel. Reason, valve stem seals these days are made for unleaded fuel in any case.

Just use normal unleaded 95 in the Lowveld and up here in Gauteng 93 unleaded."


I have been running normal ULP without any additives in Bulldog, no problems.


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