VR6 Starts then Stalls

[ip 0]

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 immobout 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.

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.

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

Cheers,

[lee060 3]

have you had it hooked up to a reputable form of diagnostics? id start there tbh .

sounds like it could be one of many things .

#can you start it and keep it revving and it wont cut out , ie does it only cut out when its left to settle to ilde after start?

#does it ever cut out whilst your just driving along?

#and i presume it doesnt miss or hesitiate?

[ip 0]

Hi Mk2Vr6Dreamer. Thanks for the reply. I should have said originally, I've hooked the car up to VAG-COM and, other than the temp sensor that I already replaced, it's clean.

When it tries to stall I can't prevent it from doing so by blipping the throttle, makes no difference at all. If there is a trick at all, it seems to be to blip the throttle a fraction of a second after it stalls (while the fly wheel is still truning the engine over). Even that might just be my imagination though.

Never cuts out when running but might miss/hesitate everynow and then (very rare though, like I've noticed it maybe four times in three weeks).

I'm stumped. Engine only has 95k on it and runs quiet and smooth when it starts. I guess I could throw money at th usual suspects (coil pack and fuel pump) but I'd rather work it out before spending a lot of cash for no reason.

[AndreWilk 1]

Hi IP did you ever find out what the problem was? I'm experiencing simialr faults.

With mine the revs drop off at ignition when the engine is warm not at all when cold though. It does also have the miss fire issue too but only very occasionally and then it rectifies itself.

Would greatly appreciate any help or advice on the matter.

Thanks in advance

Andre

[ip 0]

Hi Andre, no problem. In the end it turned out that it was just the ignition switch! Apparently they tend ot fail after about 10 years (very common).

What was happenign was that the ignition contacts within the switch would 'drop out' between switch positions. So, when cranking, all was well and the engine would start, then as I released the switch and it returned to the nornal 'run' position, the ignition voltage would breifly drop out and the engine would stall. It was less of a problem when hot since the engine would continue spinning under its own momentum for longer and then recover when the ignition voltage came back up. Does that make sense?

Easy way to verify this is to buy a new switch (£7 from ebay). This can be temporarliy fitted in approx 2 mins to test the theory. Crack open the ignition housing behind steering wheel (2 screws), reach behind ingnition barrel and remove the plug that fits into the back of the existing switch (give it a wiggle, it is plenty robust enough and should pop out easily). Now, attach your new switch to this lead. At this point you must (MUST) turn your key in the ignition key barrel. This will do two things, let the cars immob reader coil know that you have the real key (assuming you have the factotry fit immob), critically, realease the steering lock. Now, you can turn the new switch with a flat head scredriver. If the car starts and runs then you have found the issue. If not thwen at least you can check it off your list.

During investigation of my issue I heard that the immob circuit can cause this to happen if the coil reader is fecked and that the temp sensor can also cause this to happen (seems likely in your case).

If the temp sensor (blue fella on front of thermo housing) is duff then it will tell the engine that it is cold when it is actually hot. So, when hot starting, the ecu will richen the mixture which will stall the car. When cold starting, this is not an issue.

The good news is that both these issues are easily checked with vagcom. If the immob is going off then it will flag these events in the ecu memory (see immob in vagcom menu). If the temp sensor is duff then it might flag an error but even if it does not then you can simply take the car for a spin and then check the ecu temp via vagcom once it has fully warmed up. If it reads anything other than 90 degrees (plus/minus 5), then the temp sender is probably at fault (this also causes misfires). Bear in mind the dash temp dispay comes off a differnt sensor so even if this is working, the ecu might not be getting the correct data.

Hope that helps, let me know if any of it is confusing or if you want to compare results.

cheers,

ip