VR6 not starting/cutting out, Please help

[Cat VR6 10]

Hi Guys, looking for some help with start up issues on with my VR6. Basically, most times when I start it up, I have to keep my foot on the gas to stop it cutting out again. This can be anything from a short sharp rev to literally having to sit on it for about a minute. Makes for quite awkward manoeuvring trying to operate all 3 peddles at once lol. Other symptoms include dipping revs just after it starts causing the headlights to dip as well, and also hunting revs occasionally at random times through a run but not on every run. This problem has been occurring for quite some time but this morning, for the first time, I was actually worried it wasn’t going to start at all. It struggled to turn over and then sounded quite pathetic for the first few seconds.

 

So possible causes I suppose are battery, alternator or ignition switch, but would any of these failing cause it to cut out when it’s already started? Also perhaps low fuel pressure? Other than that I’m really not sure. It runs fine most of the time when it is running, it’s just this start up thing.

 

Recent relevant work done on the car is new head gasket and associated gaskets and seals, plus quite a few hoses and ancillaries including plugs, coil pack, throttle body (second hand) and new fuel filter. Also the when the garage had it for its MOT they reset the throttle position sensor and said that should help but it didn't. The problem was happening before this work was done and I had hoped it would cure it but sadly not :(

 

Is there anything I can easily rule out or test before I start replacing things? Or anyone seen this problem before?

 

Thanks in advance for any advice you can give.

Cat

[Jim 1]

From the subject I was going to say the classic VR6 immobiliser fault, but reading the post it doesn't sound like that at all. I think my next guess would be the coolant temperature sensor.

 

Presumably once the car is actually running and up to temperature it's ok? Does it return poor fuel economy?

[tony_ack 0]

Is the wiring to the idle valve okay?

[Cat VR6 10]

Hi, thanks for the fast replies!

 

It had a new toad alarm/immobiliser fitted and the guys did a good job of sorting the wiring out at the time so don't think it's related to that. It had a new coolant temp sensor with all that work a couple of months ago as well.

 

Yeah the car runs fine when warm, apart from that occasional hunting revs issue. I mostly use the car for short runs for work which return anything from 20-27 mpg depending on traffic/how much of a rush I am in ;). Not great but I think this is about normal? I have seen about 33 mpg on the motorway.

 

Will check out the wiring to the idle valve later but as the garage new about the problem last time they had it i would be suprised if they hadn't given the whole area a once over..

 

Right, back to work... :)

[stevef182 0]

Yeah I would check the ISV - quite a common problem with VWs full stop. It could be the wiring, or just in need of a good clean. Although I cant see why this would prevent it from starting, but could explain the lumpy idle/hunting.

[CazzaVR 0]

As well as checking the ISV, check all the pipework too. Take it all off and make sure all the pipes are clear. Make sure that the breather from the intake pipe is connected properly and check for other air leaks around the intake.

 

I had this exact problem on an old VR6. Took it to a couple of garages and they couldn't work it out. Turned out the sponge from inside the black plastic ISV damper pot had been sucked into one of the pipes, making cold starts a nightmare!

[Kevin Bacon 5]

If it's struggling to start from cold (and I bet the problem has worsened as the weather's cooled down) then it's either 1) Lack of fuel or 2) lack of air, or if you're really unlucky, both!

 

Jim has already answered 1) with the coolant sensor, which you counter answered with it's replacement.

 

So this now leaves a lack of air as the problem and having to hold the throttle open is a big clue to that.

 

This now points the fingers at the idle valve not opening when cold and based on what you've said, my money is on the throttle position sensor. If it's static position when closed is not 14 degrees or lower, the ECU will not engage the Idle valve as it thinks you are driving.

 

You will need VAG-COM to check and confirm this.

 

If it all checks out, then the idle valve has probably failed. Rare, but not unheard of on high milers.

 

If none of the above, it could be anything given it's had the top half removed recently.

[Jim 1]

Could still be a duff coolant sensor though especially if they used a GSF part. I don't want to get into that whole debate again but not uncommon at all for non-genuine sensors to either not last long, or be crap from day one..