Since having all manner of things repaired on my Octavia (2003, 1.6 Petrol engine - BFQ version) it has now developed another problem.

First start of the day, the engine does one of two things:

1) Starts but sounds rough as hell, and is vibrating all over the place, almost like its mis-firing, revving at about 1500, and a large plume of white, fuel smelling, smoke from the exhaust.

2) Engine will just about start, but then promptly (within a few seconds) die, will then require being turned over for a few seconds (counted up to about 7) before it will then fire again, then similar to 1) with rough running and smoke.

Once I pull off, it will even itself out and appears to be running better than it has done for ages. However, I have notices at times, when I first pull up to a junction and stop the revs sometimes rise to and stay at around 2000, until I then pull away. Subsequent journeys throughout the day are then fine, with the car starting fine with no smoke, unless the car has been sat for most of the day unused since the last journey.

I have checked, and there are no fault codes showing to help me out. So this leads me to the following questions:

1) Are there any readings I can take to try and figure out whats going on (I have the shareware version of VCDS Lite, and also Torque on my smartphone)

2) Any likely components to check/replace that could be causing this. From looking around on here it could be any number of things, but have checked for air/vacuum leaks (except for under the inlet manifold, not removed this yet). Other likely things could be the ignition system, sparks, HT leads, distributor or coil?

Car has recently had a total engine flush, new coolant pipe due to damage inc thermostat, new oil & filter, new air filter, replacement water pump and timing belt, has no apparent loos of coolant or oil, so would be nice to get this sorted to have a nice running car!

Thanks in advance.

Jon

Check your temp sender, with vcds lite you can see what temp the ecu is receiving and cross reference that with what the dash gauge is receiving. Dunno about the 1.6 but the Vrs can have problems with the sender. If faulty a OEM one is neeeded aftermarket ones fail really quickly

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had similarish issues on my escort off and on for years. A few things that seemed to make a difference were...

1) MAF sensor being dirty (just cleaned with brake cleaner aerosol)

2) MAF sensor connector was making a poor connection or no connection - and this seemed to really confuse the ECU

3) O2/lambda sensor was past its best - and Im not sure that the cheapo replacement was much use either.

4) honeycomb in the catalytic convertor started to fall apart and move around making a really noticable rattling noise. Then it seemed to create a real bottleneck in the exhaust.

Performance dropped but fuel economy improved massively!

Have you had a look at the spark plugs - can sometimes tell you something about the fuelling.

Something missed on the topic of white smoke is that brake fluid burns white. Giveaway is low fluid level, and white smoke after a hard brake . It was due to seals on master cylinder leaking and letting brake fluid into vacuum ,and into cylinders. Bit uncommon, but still possible.

Right, been spending my Sunday afternoon in a productive manner measuring things on my car!

I had already used the car today, and experienced the dodgy starting outlined in the above post. After the car had been sitting for about 3 hours I connected up the laptop and VCDS Lite, and have measured the following.

Straight away, the coolant temperature was stated in Measuring Block 4.3 as being 1.5c, this seems to be rather low, considering the coolant in the expansion tank was blatantly warmer than this, and ambient is around 18c at the moment.

I then let the car warm up, monitoring the, and also the dash temperature gauge. when the coolant temp was reported by VCDS as being 46.5c, the dash indicator was at around 70c. When the dash indicator got to 90, the coolant was reported as 55.5c. Is this to be expected, or am I looking at the wrong information here to check that the temperature sender is functioning correctly?

Also, still no sign of any fault codes being present at all.

That's got to be the temp sender then?

Registering cold and overfuelling to compensate for it hence the smoke.

Good luck hope you sort it.

Temp sender is faulty, get a new one but make sure its a genuine one as the pattern parts ones always seem to go faulty

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Cool, will try getting a replacement and seeing what happens.

Just to check though, the sensor is located in the thermostat housing on the end of the engine block. In the image, am I correct in thinking it is the one circled in red that is green and has 4 wires in the connector. This leads me to ask also, whats the other one (circled in yellow) is this to do with the thermostat?

There is not a dealer too near me, so is there really much difference between the one they would sell me, and say one from euro car parts (Dansk make, part no 460441610)?

Cheers

You've also got vw, audi and seat that you can get them from. Would keep it OEM if I was you m8

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Good point, will take a look see where any of them are around me.

The one circled in red is the one you want

Sensor now changed. This morning the old one was saying the coolant was at -10c! When I changed it, and the coolant was warm, the old one said 6c, the new one 37. Will have to wait till tomorrow morning to see if this has fully solved the problem.

All is now sorted, and the car behaving itself better than it has in a long while. As mentioned in my last post I changed the temp sensor, and this gave me much better readings (i.e. not lies). I replaced it with a part from Euro Car Parts (£15 rather than the £40 the dealer wanted), and the one I took out had no signs of it being a genuine VAG part anyway. After this, there were no problems starting the car, but it was still idling a bit rough and high to start with.

Based on that, and other threads on here I decided to investigate the state of the throttle body. When I took the air intake off from it, it was obvious it was a bit dirty, so i decided to remove it completely to see what the other side was like. It was filthy. Getting access was a bit of a pain. The picture below shows there is a metal pipe attached to the top that unbolts, and then there are several other pipes that connect to it, which I did not want to remove, but I manged to wiggle it out enough (without disconnecting the wires) to be able to give it a pretty good clean (though not perfect).

To be honest with you, I was not expecting there to be much difference at all, but from the number of posts where it is mentioned, thought what have I got to loose. In the few days since I have done it though, the care has been running significantly smoother, with a much more even idle, and no high idling at start up, so all in all seems to have been well worth doing, and will now be added to my list of things to do every now and then on the car!

Next task is to possibly tackle the spark plugs which are nicely hidden beneath the intake manifold that you can see in the picture too, once I can bring myself to dismantling all of that!