Revs up and down

[danielmjpyle 10]

Anyone any idea whats causing this?

thanks

[robrado974 1]

My first check would be the sensor that goes to the ECU. If this is old , faulty , it will be sending mixed messages to the ECU ,to much air , back to to the right amount , hence the higher idle and back down again . Also check all hoses for splits and holes . I would clean the ISV too .

[Joe3954 10]

I had a similar thing and when I drove the car and came to a stop I.e dipped the clutch the revs would not come down. Turned out to be the ISV - I was told by Brian at Jabba that they shouldn't really need cleaning and not to do it really

 

 

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[danielmjpyle 10]

Thanks guys for your replies

Ive fitted a new ISV.

When you say the sensor that goes to the ecu do you mean the one on the side of the throttle body?

Thanks

[robrado974 1]

There are three temp senders in the block , I think it's the blue one . On cold start up it sends a signal to the ECU , telling it it's cold , so more air goes in to make it idle faster . If this sender is faulty it may produce the systems in your video .

Edited April 21, 2016 by robrado974

[Joe3954 10]

rob is right - it's the blue one for water temp - you get a fast idle when it's cold and once a little warm idles normally, think they're still available from VW. Just remember to get the old O-Ring out when you change it and a smear of silicone grease on the new one and you'll be fine

 

 

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[robrado974 1]

If you connect the car to a Vagcom it will tell you if the sender is faulty , s faulty sender can cause all sorts of problems , I had a cold start problem , the sender was reading 74d all the time .,

[danielmjpyle 10]

I have replaced all three sensors already.

Yes worth a check with vagcom. Aparantly i need an adapter plug for the rado as its a different plug. Is there somewhere online i can order it from/does it have a specific name?

Cheers

[robrado974 1]

Someone more knowledgable will be able to answer the question of the leads . If you have changed the senders , have a look at the connection plugs and wiring just to be sure . Did you look st the vac hoses for splits ?.

[danielmjpyle 10]

I have two small plugs under the gear stick surround

[danielmjpyle 10]

Yupp checked the hoses, cant see anything...whats the black box that has three hoses coming in/out located next to the ISV?

[danielmjpyle 10]

Also while removing the hoses i looked down the back of the block and noticed a sensor with a few wires attached on the exhaust manifold..some of these wires look a bit suspect..could this be a cause?

[seanl82 23]

Thats for the lambda on the rear engine mount bracket. Its a possibility for sure.

The two plugs behind the gear lever are your OBD1 sockets. You can get an adapter off of ebay for literally a couple of quid to convert to obd2, so fault codes can be read. Its a little basic being OBD1, but will still make life a lot easier.

[danielmjpyle 10]

Just ordered one thanks! Ok ill get in and have a better look at the wireing on the lambda sansor...looked like at least one of the wires was broken and exposed. Just ordered a new throttle position sensor while im at it too...

Thanks