VR6 will not run when hot, why???

[Rpmayne 0]

The VR is fine when cold and warm, but when its been running for a while it starts to cut out with no spluttering, just dies.. It then will not restart until it has cooled down. Have taken it to a local garage but they need more to go on.

 

The ECU is only giving a crank position sensor fault which is generated once it has stalled. I can't see why this would be the cause only when hot. When its running the engine is smooth with no obvious loss of performance.

 

Has anyone had any problems similar with some clues I can give the garage.

 

Thanks!

[Joe M 0]

Simple stuff first, could be your ignition switch as the electrical connections will heat up a bit as well. At about £15 for the bits worth changing anyway as even if its not the problem chances are it will end up faulty soon.

[dr_mat 0]

I'm guessing it'll throw a crank pos sensor fault if the engine isn't turning anyway, so that's not likely to be the cause.

Is your ISV working properly?

What about testing the operation of the lambda?

[Rpmayne 0]

Just been on the phone to a Bosch tuneup garage and they said that the crank sensor would cause the symptoms.

 

Apparently the ISV and lambda would cause a few more problems like rough running aswell which I'm not getting, its just all or nothing. The garage the cars with has ruled out the ignition somehow already.

 

I'm thinking I might just buy the crank position sensor.. Phoned VW, they don't keep it under that name.. Is it known by anything else such as engine speed sensor or knock sensor?

 

Cheers for the help!

[PhatVR6 0]

Mine used to do that. it'd cut out at a junction, then when I'd restart it, it'd rev up and down on it's own then cut out if I touched the throttle.

 

If the crank sensor is faulty the car won't run at all. mine evetually went like this. I just took it out and cleanded up the surface of the block where it mounts (it earths through it's body voa the block) and it was fine after that.

 

I can also be called and engine position (or speed) sensor.

[dr_mat 0]

The "Engine Speed Sensor" is listed at £140, not something you wanna replace "just in case"!!

[Geo 0]

Just been on the phone to a Bosch tuneup garage and they said that the crank sensor would cause the symptoms.

 

I'm thinking I might just buy the crank position sensor.. Phoned VW, they don't keep it under that name.. Is it known by anything else such as engine speed sensor or knock sensor?

 

Cheers for the help!

 

It could be down as engine speed sensor but not as knock sensor, that's a seperate sensor.

 

As regards what the cause of your problem is, it may not be the sensor itself that is the problem, but the connection to the sensor. Try and find the plug going onto the sensor, then try moving it around a bit with the engine running, if the engine stalls or the idle speed changes or fluctuates then you know you have a problem but whether or not anything happens try doing the following anyway before you go and buy the sensor. Take the plug off and clean the contacts and put some contact oil on them then put it back and see what happens.

 

I've seen several cars with symptoms just like you have described that were cured by doing this.

[dr_mat 0]

Yeah - the sensor itself is just a solid state coil. It's not likely to "wear out" as such, it's more likely the connections.

[Kevin Bacon 5]

For info, VW class all of the magnetic sensors as "Impulse senders".

 

They are wear items, the magnetic strength of the magnet/coil can subside with age and then it will lose it's resolution, i.e. not provide a true square wave. If the ECU sees a drop in waveform output and digital definition, it will cause running problems.

 

There are 3 error conditions for the magnetic sensors:-

 

Implausible signal

Short to ground

No signal

 

If you've got the 1st error, replace the sender. If you've got either of the other two, check the wiring.

 

K

[PhatVR6 0]

try cleaning it and cleanign the block too. it's free, and it sometimes works.

[Kevin Bacon 5]

Only if the end of the sensor is caked in swarf and emulsified oil.....

[Rpmayne 0]

Thanks people, I've passed on the comments to the garage. Thinking about it the block has been painted and I used some sealant around the o-ring. Maybe a bad earth but thinking the bolt would still make contact. Didn't realise how much those sensors are, buy inductive sensors at work for about £30.00. Definitely won't buy one to rule it out.

 

They are going to check all that for me and hopefully that will sort it. Thanks again!

[PhatVR6 0]

don't use any grease or anything on the sensor. it needs to be bare metal and squeaky clean to work properly.

[Rpmayne 0]

Alright all, the VR's still down the garage having made no progress with the problem.. Just a couple of extra clues if anyone can help. Sorry to keep asking so much but I'm having difficulty finding people who have worked on VR's:

 

1. Very consistently stalling when hot, oil being over 70deg. C.

2. Sometimes starts again. When it doesn't I can smell unburnt pertrol out the exhaust.

3. VAG-COM doesn't always report errors at this point. G28 Engine speed sensor occasionally occurs.

 

I'm thinking that everything else is working other than the sparks if there is fuel being delivered. Doesn't splutter when it stalls, just completely cuts out. Same when starting again, all or nothing.

 

Could it be the Coil pack?? Must be some problem common to all of the plugs. Does the VAG-COM get any feedback from the coilpack to tell whether its working or not?

 

Thanks!

[Kevin Bacon 5]

Nah the coipack isn't monitored.

 

Have you tried replacing the engine speed sensor? Sounds like that's what it is to me. It's losing it's resolution.

 

Or try one from another VR6 if possible as the sensor costs £140 from VW.

 

K

[Rpmayne 0]

The problem is I don't know anyone who has a VR6 near me. Might give a few scrap yards a ring to see whether they have one. Its the sensor mounted on the front face of the block yer, bottom right corner?

[Kevin Bacon 5]

Yep, just to the left of the bell housing cover.

[Rpmayne 0]

Cheers mate!

[Geo 0]

In a healthy car when you turn on the ignition the fuel pump should pump for a second or so and then stop. Then when you turn to the start position the engine speed sensor should give back the signal to the coilpack and the fuel pump to operate so that the engine will start. So, you've already established that you have no spark when the engine is turning over. So now check to see if the fuel pump is operating when the engine is turning over but not starting? If it is working then the engine speed sensor isn't the problem and you could be looking at a coil pack issue. But if the fuel pump isn't pumping then you can be pretty sure that the engine speed sensor is faulty.

[Rpmayne 0]

Have just this second ordered a sensor from the b**tard stealers for £140.00, just gonna try that now because the amount of time the garage is spending trying to sort the problem will probably cost me that.

 

There was a strong smell of unburnt petrol when the engine had got hot, stalled and on turning over to restart. Should get the sensor tomorrow morning so i'll find out either way then.

[Rpmayne 0]

Update to this problem.. Received the new crack position sensor, removed the old one which had no signs of mechanical damage and replaced it with the new one. I took the new one out again to check it was sitting correctly and it had a layer of fine metal dust on it, was standing up cos of the magnet. Thought the oil might be too dirty (2nd change after the rebuild) so changed it again. Problem still there.

 

Had another thought.. How does the rev counter work? When the engine dies the rev counter still displays the engines decreasing revs. If it gets its signal from the crank position sensor it must be ok.

 

Now I know the oil change didn't fix it (hopeful I know) I might just change the sensor tonight to eliminate it.

[Geo 0]

The rev counter gets its signal from the alternator not the crank sensor.

[Kevin Bacon 5]

Ay? How can one revolution of the alternator pulley be the same as one revolution of the crank?

 

The VR6 takes it's RPM signal from the crank sensor.

[Geo 0]

Ay? How can one revolution of the alternator pulley be the same as one revolution of the crank?

 

The VR6 takes it's RPM signal from the crank sensor.

 

Well obviously one revolution of the alternator won't match up to one revolution of the crankshaft but you can still work out the engine revs from the alternator.

 

As regards the VR6 system, I've never looked so I'm sure you are right but the vast majority of cars with rev counters take the reading from the alternator.

[dr_mat 0]

I think the cars take the rev counter reading from the engine speed line out the ECU, afaik...