cliffcoggin

Was the replacement battery new or secondhand? Did you get it coded to the car?

https://duckduckgo.com/?q=what+oil+to+use+for+a+AudiA3+Sportback+2019+1.0+Petrol&ia=web

Doesn't it tell you in the handbook in the car?

Glad to hear the problem has been resolved. Dare I ask who paid for the replacement engine? My speculation is that the old engine had been worked on in the past by somebody incompetant, who had either over-tightened the new cap bolts or re-used the old bolts, and at the same time somehow mis-aligned the oil pump drive. What that does not explain is why oil only leaked when the car was stationary.

A faulty valve spring is possible, but unlikely. More likely is a worn valve guide allowing oil and gases into the rocker case and crankcase. It appears you have the head off so now is a good chance to remove the valves and check their seats and guides.

Richard. I suspect a complete door, or components thereof, has been fitted from a different model. The previous wiring repairs complicate matters even more. What is not clear to me is what parts of the central locking are not working with which control units. The drivers door or the other doors? Using the key or the remote fob? It is possible the new controls need to be coded to the car, but I am unsure on this point.

Well who'd a thought it? Thanks.

I did not know a fuel temperature sensor existed on A3s. What is its purpose? I could understand diesel temperature being important in cold climates because diesel can throw a waxy sediment when it gets cold, but surely not in Newquay?

Richard. Before spending more money, check the wires in the door. It often happens that they break in the rubber bellows between door and frame.

More fouling of one valve than the others, plus the misfire on one cylinder, plus excessive EGR fouling suggests wear of the O-rings or bore. That's not altogether surprising on a twenty year old car. How many miles has it done? A compression test will be enlightening.

Do please let us know the outcome.

I guarantee it will, and empty threats of court action will not change that. Please consult a solicitor before you throw any more money down the drain.

In that case it is almost certain the thermostat needs to be renewed. It isn't a difficult job, but getting rid of the inevitable airlock afterwards can be. (If the cabin heater does not work after changing the thermostat you have an air lock.) Let us know if the engine reaches normal temperature afterwards and we can then move on to the fan problem.

Zak. This may seem an odd question, but it is not trivial, and may be relevant to the problems. How old is the battery?

The thermostat does not control the fans, that is the job of the temperature sensor. (Strictly speaking, any switch that is controlled by temperature is a thermostat, but let's not be distracted by that as it is contrary to convention in cars.) That the indicated temperature goes no higher than 70 without the fans suggests to me that either the thermostat remains open all the time or that the temperature reading is wrong. Does the temperature reading drop to the bottom of the scale when the engine is cold? Do you have a way to independently measure the temperature using a hand held infra red meter for example? At this stage I can not say whether the ECON fault is related to the temperature fault. I suggest you ignore it for the moment, but bear it in mind if you get other indications of a general electrical problem.

I could not agree more. Why throw more good money after bad? It's unfortunate that if one wants to buy a cheap secondhand car one needs to have enough knowledge to know what you are letting yourself in for in terms of fault rectification. This applies much more to any vehicle that has been mapped or modified in regard to DPF or EGR removal because it is so much harder to obtain good free advice.

Add an air lock to the list of possibilities. Has the cooling system been opened recently, to fit a thermostat for example or change a hose?

John. You have not mentioned how much you paid for the car, but I doubt it was a lot considering its age and mileage, in which case I fear it will cost you more in money and time to get recompense than the car is worth. I suggest you swallow the bitter pill and accept that you have been conned, then move on to either repairing or replacing the car.

They are Bowden cables: thick slightly flexible rods.

I'd agree it is a fault in the linkage rather than the gearbox. The cable adjustment may have loosened at the gearbox end, or the cable mounting bracket may be loose. You will need to examine the whole linkage to find where the slack is. I have not done the job myself but the Haynes manual suggests a complicated juggling of springs and locking collars to detach the cables.

If transporting the dogs is so important to you the logical thing to do is get rid of the TT and keep the A3.

Emma. I would largely agree with Jason that repair costs are going to increase as the car ages and wear accrues. So from a maintenance perspective it would make sense to get rid of it, but that takes no account of sentiment. On the other hand what are you going to replace it with? An expensive newer car will likely have fewer faults and lower maintenance costs, but a cheap old banger will be worse than your existing car. As the old adage goes "sometimes better the devil you know". It comes down to what you can afford to invest against the cost of keeping the A4.

The same issue gets the same suggestions. Have you tried them?

And thanks again to Joe for his analysis which I have marked as a solution.

Take it back to the dealer under guarantee.