VR6 Starts then Stalls

[iep]

Hi, I've just bought a fairly tidy '95 Golf VR6 which is mainly sound but has one odd starting problem that didn't occur in the first week I had it but now occurs all the time.

When starting the car at any temperature, the engine fires up nicely, runs at the right RPM and then, after a second or so, stalls. After a few attempts (between 2 and 20) it will generally catch itself as it stalls and manages to recover (followed by 5 secs or so of high rpm tickover). If the car is hot, it still tries to stall but seems to be better at recovering (manily starts in a 1 or 2 attempts). I've replaced the thermostat (needed done anyway), both temperature sensors on the thermostat housing and also taken the immob out of circuit to check whether this was the issue. None of these things have made a difference to the starting problem. On the upside though, changing the thermostat has improved mpg.

I should add, it never cuts out when running and I don't think I'm seeing any missing/hesitation.

A mate suggested the ignition switch but I don't see why the slight temperature dependence would exist if the ignition switch was dropping out.

I've also checked it out with vag-com but now that I have replaces the temp sender, everything reports back as fine.

If anyone has any thoughts, please let me know and I'll post an update to say how I've got on.

Cheers,

[brybrybry]

Sounds very similar to a fault i had on my Golf GTI, it would start randomly and cut out a second later, also had some running issues with it though. Running issues turned out to be a faulty ignition coil, and cutting out issues have been fixed since i removed the reader coil from the ignition barrel and re fitted it.

[iep]

Okay, this sounds very promising. I'm pretty sure the coil pack is good but there has been one oddity with the ignition barrel already (for some reason the switched feed to the radio just stopped working). I wasn't aware though that there is a reader coil in the ignition barrel.

Could you have a shot at describing where the reader coil is on the ignition barrel? Is it tough to remove?

Thanks for the response, iep.

[brybrybry]

It may be different on the VR6 but i would assume its going to be similar, someone else more qualified may be able to confirm, but basically i took off all the covers around the steering colum and the reader coil is located around the ignition barrell, i have attached the picture i took when doing this, quality isnt great but it should be ok.

I just followed the cable back to where it was plugged in took the unit off checked that it was ok and plugged it back in, havent had any starting problems since doing this. I did order a new coil but the connecter was different so i didnt end up using it. It also helps if you have long thin arms as following the cable back and getting your arm up into the dashboard can be a bit tricky

[iep]

Thanks again. Useful info. I took a quick look at mine over lunch and it looks pretty much the same. For the record, I also (on a colleagues recommendation) bought a new fuel pump relay. Made no difference.

I'll trace that coil reader wire back later on and give the connection a quick clean as you recommend.

[Crasher]

The fuel pump relay hardly ever fails but the ECU relays do. It is the one at position 3 with 109 printed on top and is VW part number 1J0 906 381 A and costs £13.48. I suggest you have a fault code read done before you go any further. During 95, VW switched to a throttle body with stepper motor control for the idle from the previous separate idle valve, which does yours have?

[iep]

Hi Crasher. Wish I' known that before. Never mind though. I'm happy to spend another £13.48 if it will fix it.

I've searched for fault codes using VAG-COM and apparently everything is fine. No fault codes at all since I replaced temp sender (G62).

Not totally sure whether I have the idle valve or stepper motor. I know what a stepper motor throttle body should look like (I had a stepper on my last car, 98 polo) and I don't see anything like that so possibly the idle valve version. Does that indicate anything to you?

Currently I'm starting to suspect the fuel pump and have ordered a fuel pressure test kit to check it out. I'll keep you posted.

[iep]

Just rechecked engine with VAG_COM and noticed that the air intake temperature was 61.6 degrees (pretty much fixed). Needless to say, Edinburgh is more like 10 degrees right now. I'm guessing this sensor is dead but not a short or open circuit and so does not flag up an error (since 61.6 degrees might just be feasible for the car if it were in scary hot parts of the world). Either way, does anyone know where the air intake temp sesnor lives on a 95 golf vr6? Thanks again.

[Crasher]

It is on the side of the inlet manifold on the runner for cylinder six and it reads a very high temp due to its position.

[iep]

Hi Crasher, found it this morning and unplugged. Made no difference. Will reconnect this afternoon and make sure that it starts at a low temp before heating up. Thanks for the advice.

New observation is that the engine keeps runnign fine as long as I keep cranking. If I blip the throttle it responds nicely, no problem. Then, release the key back to normal 'run' position and the engine stalls immediately.

Could be ignition switch itself? Anyone know of any other comp[onents that could cause this. Since it continues to run fine if the ignition is still in the 'crank' position I can't believe that it is fuel startvation any more.

[Crasher]

Did you observe the measuring block to see if the display went to -40 odd?

[iep]

As I understand it, when the temp sensor is open circuit (since I removed it) the result flags an error in the ECU and the temp defaults to 20 degrees C. This is what appears to have happened on mine. A bit of searching around suggests the normal figure of 60 degrees C (that I was seeing when the sensor is plugged in and the engine warm) is normal. So, probably not the temp sensor.

So, ordered myself a new ignition switch (£5 offf ebay) and will try this out tomorrow. Easy test, unplug connector from existing ingnition switch (which is in barrel). Attach new ignition switch to connector (just hanging off end of lead). Insert key into ignition barrel (so reader coil from immob will detct legit key) and then used screwdriver to turn paddle slot in new ignition switch. See what happens. This test set up should allow me to rule out ignition switch and immob as possible causes (if car still does not start I can remove key from ignition barrel. If behaviour changes, it's not the immob). Only costs me £5 and might show up something.

[Crasher]

The map will default; I wondered what the display read. When doing that with an ignition switch there are two points. I knew someone once who forgot about the key in the ignition and drove the car, not good and not me, but you are not likely to do that due to the transponder. Secondly, these cheap switches work fine out of the car but I have had problems when they are fitted, they would not allow the starter to turn due to the body being incorrectly indexed during manufacture. These were black in colour and I tried seven!

[iep]

The block measurement on VAG_COM read 20.3degrees C. I understood that VAG_COM only allows access ot the map values.

Good comment on the cheap switch I have read of other people who tested the switch outside the barrell and found it did not work once fully installed. I'm using mine as a proof of concept. Assuming all goes well, I'll get the real deal from VW.

I don't think I'm following your point though about forgetting the key in the ignition. What exactly did he do?

Thanks again.

[Crasher]

That’s what I hoped it would say; otherwise you may have had a wiring fault.

The friend of mine drove the car without the key in and the steering locked.

[iep]

Steering lock, good point. Short journey then.

I'll post any findings once I've checked out the new switch. Fingers crossed but I'll admit that I'm starting to lose hope. I've tried a lot of stuff already. Only things left would be the ECU itself (though it seems fine at all other times) or some odd fault where the immob finds, then loses the signal from the ignition key. Wouldn't begin to know how to fix that.

Anyway, thanks as ever for your thoughts.

[iep]

Just spotted this in another thread:

If it was the factory fitted immobiliser that would cause the car to start and immediately stop again and would not cut the car out when driving but it would leave a fault code on both the engine and immobiliser ECU's.

So, assuming this is true, the immob would let my car start and would then kill it (matches behaviour) but would also leave a fault code on the ECU (does not). Anyone know if this is accurate info? If it is, I can stop worrying about the immob and focus on other possible issues. Winner.

[Crasher]

If it was the immobiliser, it should leave a code for unauthorised start but sometimes only in the immobiliser and not in the engine ECU. Have you scanned the immobiliser?

[iep]

Yeah, scanned both engine and immob. No faults reported. Got switch today, will hopefully get a chance to try it out this evening. Fingers crossed.

[iep]

HI Crasher. BTW, switch I got sent is made by TOPRAN and doesn't seem too shabby. Has the correct VW part of the packaging. Do you happen to remember the make of switch you had trouble with?

Cheers.

[iep]

Tried out the new ignition switch this evening and it fixed the problem totally. Would never have initialy guessed that this could be the issue but it starts fine every time now. Totally chuffed. With a new switch only costing £7 I think it is well worth trying one out (dead easy, you don't need to install it into the barrel) if you have any odd starting/cutting out problems.