Seriously weird problem with GTI 16V

[Gavv8]

Is the immobiliser part of the alarm system? as most are or can be wired in to the cooling fan to allow the fan to run on for a while after the alarm has been armed without setting it off.

[dazmatic]

Nah, it would look like there was a scorpion alarm system fitted by the dealership and then later removed as the alarm horn is still under the bonnet.

This immobiliser is a laserline and fitted sometime later.

Trouble is, I've just done a thorough test of both ECU and fuel pump relays and it is neither of them. I've also pulled the aforementioned fuse out again and went for a spin.
It still kept hesitating again and then eventually cut out and died when it reached 86oC on the oil temp gauge.

I've decided I've wasted far too long trying to fix this now and am going to either sell it spares/repairs or scrap it.

Can't be dealing with it anymore.

[dazmatic]

Well, I've completely changed my mind.

I've put my polo up for sale instead and im keeping the golf for a bit longer to try and fix it.

Is it possible that the new crank position sensor is faulty?

Is there a way of testing it? I've got an oscilloscope but not sure whether any fault would show up on it if I tested it.

[Ninja]

Crank sensor worth a check. They become wet and corrode over time resulting in cutting out etc. also, check ecu earth under battery tray. Make sure wire isn't black inside as water gets under tray and burns wire inside out. If this is the case, you can re wire an earth back to the engine block.

[Leon27]

As above - I had issues with corroded wires under my battery tray too.

Can you possibly tell if you are getting fuel supply when the fault happens?
Check that your alternator isn't overcharging, it activates a over voltage protection thing inside Relay 30 which cuts power to the ECU to protect it. My engine would hesitate during it's few seconds of overcharging but it never cut out.

With your oscilloscope you should get a square wave pattern like an on and off then probably a longer square wave which represents TDC, i don't know what pins to test without looking tbh but if it were to fail at a certain temp then the pattern would be anything but a square wave. However when it's hesitating it could be like the sensor is failing so you might see something there.

If you are getting fuel supply right up to the injector rail when the car cuts out then you can rule out the pump/filter/relay 167.
But basically when the engine stops there's no spark so from a diagnosis point of view it's complicated because the crank sensor signal along with the hall sensor in the dizzy is used by the ECU to determine when to tell the coil to spark.

It's not unheard of for new crank sensors to fail, especially the cheaper make ones. That and the coil are known to fail when hot.

[dazmatic]

Hi there,

Haven't replied for a while, had given up on the car.
The tax is due at the end of the month so I either fix it or it goes.

Trouble is, I've now replaced the fuel pump for a known good one and I've tried to recreate the problem by pulling the relay. When doing this, the car cuts out BUT slowly, as the pressure drops.

The actual problem is more of an instant loss/regain, like ignition cutting out rather than slow death. It can't be the coil as it's stone cold and has also been replaced for known good.

Also, I don't think it's the hall sensor in the dizzy as I've disconnected it with the car running and the car carried on running! (didn't throw up any error codes either which was strange)

I've watched the signal on my scope from the crank sensor and your right in that there is a square wave pattern and a long wave for TDC. I watched the signal whilst the car was cutting out on the drive and the signal stayed a constant square wave.
I think it's safe to say that it isn't the CPS which means this second new one I've bought is redundant.

I'm completely lost now, not a clue!

[spikenipple]

Perhaps the ECU itself is to blame? 

[dazmatic]

I'm pretty certain its a temperature thing.

Soon as the oil temperature reaches 86/88 degrees Centigrade, that's when it starts cutting out. It will run lovely up until that temperature. I'm thinking that maybe perhaps it's something to do with oil temperature or something?

[husky jim]

Engine temp sensor? I had the same problem changed everything then after bein told to change the crank sensor it didn't do it for a while then came back. Then changed the engine temp sensor and as soon as i changed that it never did it again ane that was 3 years ago.. worth a punt for less than a tenna part

[dazmatic]

Which temperature sensor was that and where is it on the block?


I know that there is two water temperature sensors, one for the dash and another for the engine to control the fan.

But what about oil temperature?

Is it the same case that there is 2 sensors for oil as well, one for the dash and another for the ECU?

I put my VAGCOM on it last night, no codes at all.