cliffcoggin

What I am wondering, and at the moment it is only speculation, is whether the excess crankcase pressure you reported last year is responsible for the present problem. If the engine is blowing a lot of lubricating oil into the intake manifold it might explain the slow cranking on the starter motor, the blocking of the DPF, the clouds of smoke, and the runaway engine. Under the right (or perhaps I should say wrong) conditions diesel engines can run on their own lube oil. What is the mileage of the car? What is the oil consumption? What is the general condition of the engine?

Is this the same smokey engine you asked about 20 months ago? If so, what was the solution at that time? The obvious candidate for the smoke now is the DPF blockage. Whether that is also the cause of the uncontrolled revving seems unlikely. Possibly both problems are symptoms of a more fundamental fault with the engine. Runaway diesel revving is a serious problem and invariably ends badly, so it needs to be diagnosed and rectified before returning the car to use. I would even go so far as to say the car is dangerous.

As the problem began immediately after a service I would take the car straight back to the garage that did the work. I am not saying the garage is definitely negligent in its work, but it surely has a responsibility to ensure the car is returned to you in no worse a condition than when you took it in.

Have you read this topic? https://www.audiownersclub.com/forums/topic/18824-audi-a3-8p-everything-is-flickering/

Chuckle. You didn't expect him to return any more than I did Gareth.

It could well be the oil pump or some of the main or big end bearings. It could also be a timing chain or a hydraulic valve depending on the engine, which you have told us nothing about. No sensible answer can be given until you give us some details. How many miles has the car done? How old is it? Does it have a full service history? And just to be clear, are you are saying the problem only appeared after the service?

It makes sense to have every pad by the same maker so that the co-efficient of friction, and hence the braking effort, is the same on all wheels. (Pad compositions vary slightly from one brand to another.) I doubt that holds true for the discs as the steel is made to the same specification no matter who actually fabricates them. I have never heard of Klaxcar, but then I long ago gave up worrying about brand names after reading that the name on the box often had nothing to do with whoever made what was inside.

I have long been critical of the total reliance on computer diagnostics, untempered by any human thinking or experience.

It's disturbing that a professional could not discover such a simple fault for so long, but having happened once it is possible it has happened again. I suggest you take that cable off and clean the terminals with sandpaper or a wire brush. Ensure the screws or clamps are tight when you refit it.

Maria. It may be a defective instrument panel. See this topic for more information: https://www.audiownersclub.com/forums/topic/21817-electrical-fault/

Glad to hear the end is in sight.

Well that confirms there is a real problem. Do let us know the outcome.

I had forgotten about the filter which may be blocked. It is normally changed on a regular basis, perhaps every two years if I recall correctly.

I believe you are right about the flap being stuck, but I know of no way to test it without dismantling. On second thoughts, how about wafting a little perfume by the external air intake. If you then can not smell it inside the flap must be closed.

Have you tried the tip immediately above your post? Have you even read it?

I am puzzled how the cooling system can have been flushed as you claimed earlier without opening it. Be that as it may, your other information confirms that the cooling system, including the thermostat and pump, is functioning as it should. Your heater problem then can only be either a physical blockage such as a kinked hose, a closed valve, a piece of debris, a clogged matrix; or an airlock.

Stephen, you have not answered Gareth's question about how soon the engine gets to normal temperature, to which I will add two of my own. Does the engine overheat, and has the cooling system been opened or drained?

In addition to Stevey's comments, check the fuse. As far as I recall there are separate fuses for left and right headlights.

If the cooling system has been opened or drained there is a good chance you have an air lock preventing flow through the heater matrix. An internet search will show a few methods to shift the airlock, but I have not faced the problem myself so I can not say which ones work.

In summary: cold starting is fine, hot starting is erratic, and the engine runs well once started. If that is correct I suggest there is an electrical or mechanical problem, though that doesn't narrow the field down much. ECM, mass flow sensor, crankshaft sensor, exhaust sensor, fuel injector, and many more could be at fault. I doubt we shall arrive at a firm diagnosis from discussion on this forum, and guessing at answers will be expensive for you, so I suggest you get it tested at an Audi dealer or independant Audi specialist. Do not use on an OBD reader from Ebay or the like, they are unreliable.

Petrol or diesel?

A simple voltage test will not always reveal internal battery faults, nor will such faults necessarily interfere when used in another vehicle. If the problem occurs again I recommend you fit a new battery before spending a lot of time and money on sensors.

Was that a new battery you fitted or a secondhand battery? Dodgy batteries are known to disturb the cars electronics leading to apparently unrelated warnings, false error messages, and symptoms such as limp mode.

Good. How much did it cost to have repaired if I may ask?

Tested by whom, and in what way? That the fuses are OK is irrelevent; it is the circuit board or its components that get damaged as I understand the matter, though I must add that is the full extent of my understanding.