Engine Warm Up

[teknow]

I've been having a problem with my car where it either jolts or cuts out completely with no EPC light after about 10 miles.

I live half a mile from the M6 Toll road and drive along it every morning. I've noticed this problem happens at about 10 miles [if it happens at all!]

Is it conceivable that if I've driven 10 miles at a constant 80mph that the oil is still heating up? I presume the coolant would have reached a constant temperature by this point??

Am just trying to work out why it would be related to the distance I've covered ... maybe just sods law at work.

Your thoughts are always appreciated.

 

[davecash]

Oil will be up to temperature around about that time, if not a little before with such a constant high speed. I'm not sure how oil temperature would relate to your issue though.

 

[teknow]

Well we all know that I should probably invest in VAG-COM and see if this helps, but this problem has been happening on-off for 2 years now and every time my local mechanic services the car he says there are no faults logged - bt he uses an OBD type thing and not VAG-COM.

However, my line of thought is like this:

1. It could be an oil temperature/pressure sensor if there is such a thing. I read somewhere that there is an if you pull the cable off the sensor with engine running you get the 3 beeps of death and the engine stops with no EPC light. This is what happens to mine.

2. The heat disapating from the engine eventually warms up the crank sensor to the point where it doesn't work any more. Aparently electromagnets reduce in performance as they get warmer. If the magnet is faulty or producing a low reading in the first place then it can get to the point where it heats up and can't read the flywheel.

3. Something else.

It seems there are more and more people hitting the same type of fault and nobody has managed to find the answer yet.

Another guy on here, snoopdog has his beezer in the garage at the moment to try and find the cause.

In my case, problem is it only happens every few weeks. Then I might go through a spate of it happening every day. But for the last 3 weeks nothing .... not a hiccup!

Driving me nuts now!

 

[StanTheMan]

Coolant temp sender or coil packs breaking down with heat.

When was the car last serviced including filters and plugs?

 

[teknow]

Stan - thanks for reply.

Last serviced May at 78,000 miles. Oil, filter, spark plugs, etc.

Interestingly it failed the MOT on emissions which were way out - mechanic says he changed the plugs and it passed with flying colours.

Does that help?

 

[DodgyDave]

Stan's on the money here i'd say

Coolant Temp Sender (or sensor ??) - it passes the temp of the water-coolent in the engine to the ECU & Dash, but it has TWO sensors in it i believe (one ECU & one dash).

I've had this go on my Leon and you get 10-15 mins of normal driving then a CEL on the dash - turn engine off/on again and it's fine for a while.....

As for emmisions - the ECU thinks the engine is hotter/cooler than it realy is so changes the fueling to match - so fueling goes way out ......

Cheap to change at under £20


Dave

 

[teknow]

I've already changed the coolant sensor but this problem is so intermittent that I guess I won't know for a while!

I'm surprised that the EPC light doesn't come on as soon as it happens and stay on! Bit of a crap design that?!?

As the memory of my ECU has not been cleared for ages, should I find a fault code if I plug in VAG-COM? Or is this fault not recorded?

Why have TWO sensors? Why not have one? What a daft idea ... so what we are saying here is my interior coolant temperature sensor could is saying 90c constantly and the sensor that actually does anything useful could be screwed and causing my valves to overheat and god knows what else?!

Blimey .... I'll never understand cars ....

 

[teknow]

Just to keep you up to date.

It still hasn'y happened but a guy called snoop on here has had the same issue (sounds like it). We've been keeping in touch for months now ... his turned out to be the G28 Engine Speed Sensor (crank sensor).

The mechanic did a continuity test on the old one and when he wiggled the wires to it, was producing dodgy readings.

he reckons the wire gets baked by the heat from engine and eventually the core of the wire goes brittle and hard.

So - when I'm in for my next service I'm gonna get the sensor changed anyway as they are £60 + fitting.

Hope this helps someone ... I've been suffering intermittently for years.

If Seat dealers made diagnostics AFFORDABLE and not try to rip us all off then I could have solved this years back and they would have had my cash!

Rant over.