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lupo gti kangaroos


henry
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Hey all,

My gti seems to do a what feels like a kangaroo lurch when throttle is released. Car is well over due a service. Don't think fuel filter or plugs have been changed for a while. Only had the car a few weeks. Any help would be greatly appreciated :) thanks all.

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The temperature of the engine shouldn't make any difference at all when it's controlled by an ECU.

If you are getting wierd behaviour when cold, chances are something is not right. The ECU rev limits lower when cold, but most people don't generally cane an ice cold engine, so don't notice. The car should feel almost identical from about -20c all the way up to 50c (ambient air). Sure power will be down when it's cold, but for normal driving this should not be noticable.

Lurching or kangarooing (or hunting) depending on your favourite word(!) is usally due to a fuel fault, where the air-fuel mix isn't right. Either too much fuel or not enough (or too much air or not enough). Often caused by a sensor or an airflow control mechanism being sticky.

This applies to almost all modern injected engines.

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The temperature of the engine shouldn't make any difference at all when it's controlled by an ECU.

If you are getting wierd behaviour when cold, chances are something is not right. The ECU rev limits lower when cold, but most people don't generally cane an ice cold engine, so don't notice. The car should feel almost identical from about -20c all the way up to 50c (ambient air). Sure power will be down when it's cold, but for normal driving this should not be noticable.

Lurching or kangarooing (or hunting) depending on your favourite word(!) is usally due to a fuel fault, where the air-fuel mix isn't right. Either too much fuel or not enough (or too much air or not enough). Often caused by a sensor or an airflow control mechanism being sticky.

This applies to almost all modern injected engines.

Interesting reading mk2.

Mine will lurch for the first 10-30 seconds I'd say, then it's fine, and again only really when in first. To be fair it's unlikely the engine has actually changed much in temperature in that time, however the problem only seems to occur at all when it is very cold.

The last service the car had suggested replacing the air and fuel filter (and something else, I forget what) - my Dad is of the opinion that basically the engine has too many things working against it when the car is first started and this is the cause of the lurching.

henry - you'll probably beat me to getting around to a service but once I've had one done I'll let you know if it sorts the issue!

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They all do it when cold, it's just a quirk of the GTI. Allegedly if you run them on 98 ron rather than 95 ron petrol then the kangarooing isn't as bad. I've always ran mine on Shell's finest and both the GTI's I've had still did it.

If you have a problem when the engine has warmed, then first thing to try would be a decent service and some decent fuel. Also, there is no carb or airflow meter to clean...

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They all do it when cold, it's just a quirk of the GTI.

It shouldn't do it. Imagine if you'd just left the showroom with a brand new GTi and it did it.... you'd be right back.

If it does it, it means something is wrong...... somewhere. Now the question is where? That I don't know.

My guess is that it would have something to do with the airflow at idle, and the idle control system (the ECU demands more air and then less air and you start to get an oscillation, or hunting). I'd try a different throttle body if I had one handy to eliminate it.

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I know they probably shouldn't do it, but they do. It's something that has been discussed often before on the forum:

https://www.google.co.uk/webhp?sourceid=chrome-instant&ion=1&espv=2&ie=UTF-8#q=site:forums.clublupo.co.uk+gti+kangaroo+when+cold

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The reason they are jumpy when cold is because the engine is based on the Super 1600 Rally engine, which is designed to idle much higher than on a road car. Mine is very jumpy when cold, I have learned to adjust my driving style until she has warmed up a bit. There is nothing wrong with the engine, it is just the way they are.

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I've just asked one of my mates at a 'large German electronics company' what he thinks causes this effect on a DBW car, as I'm curious too.

On the smaller engines (below 2L), it is usually a slow throttle valve and/or a light film of dust on the air flow sensor. What apparently happens is that the revs of the engine don't match where the air flow sensor is telling the ECU the revs should be. The ECU compensates by closing the throttle a bit, but more than it needs to because it is being tricked by the sensor. The anti stall (idle) program then kicks in and suddenly opens up the throttle again to keep the engine running smoothly. But if there's a delay in the opening caused by a sticky/stiff throttle valve, the amount it is supposed to open by is not enough, so the ECU compensates still more. Then you get an oscillation going where the ECU is trying it's hardest to keep up.

Also air leaks can cause trouble as the airflow sensor will be providing a different reading to what the engine is actually breathing. The ECU will see less air than is actually being provided, but it does have an air leak program/table it can run, which will compensate a bit. I once found a brake servo was leaking air quite badly on a Mk4...

The throttle is meant to work very very quickly. It should snap shut. Besides the spring pressure, it should be smooth and light. Lack of lube or wear will cause it to be stiff. In addition, the built-in TPS can also wear, which is why they have now switched to hall sensor TPS systems.

Worth trying- pull the throttle body and clean and lube it.... Wash out the airflow sensor with warm soapy water. Personally I'd use a cotton bud (or Q-tip if you're American!).

I don't have a GTi, but from what was explained to me, it makes sense.

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I have

Sounds like a good explanation and makes complete logical sense.

It's also a mapping issue with the earlier GTI's.

Trust me, I've had two GTI's, whack some 98ron fuel in it and itll go.

I have always used 98/99ron and it has always been there, doesn't bother me though as i let it warm up for a minute then it goes

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