This time an example, what to expect if you:

a. buy a car without proper diagnostics;

b. the repair has been done by yourself, without appropriate knowledge, and using “original” methods;

c. what consequences and expenses to expect;

d. is it possible to save on something.

The owner of E90, more than 10 years old, approached me. N43 series petrol engine. The engine runs unsatisfactory – vibrates strongly, shivers, does not have power, etc.

”…Bought this car I while ago with this problem.

It runs very rough.

First of all, there were several fault codes with the fuel pressure.

Already swapped the LP sensor three times, HP sensor 2 times, HP pump 2 times, checked timings of the engine, bought new Vanos solenoids, and so on.

The car is running very, very rough, but it runs for a few minutes fine from time to time.

After every swap of a component, I cleared the adaptions.

When compiling the report for you, the coolant pump died..”

The fact that as if replaced spare parts were replaced several times caught my attention. If you install a new part, you don’t do that, right? Obviously, in this case, used spare parts were installed. The owner of the car was not hiding it:

”All parts was .. used parts.

Most of them were changed 2 times.”

Here, the first fundamental mistake. Why is it not smart to install used parts? With a substantial probability, the wear of the “new” part could be much larger than for your car/car parts. Of course, it can happen, then somebody destroys his loved, slightly used car, which was maintained in a perfect technical condition, but the owners of the car dumps usually keep parts of such cars for themselves or their friends. If you are not a “close” person, you will not get such parts for a low price! Second – you don’t know what fuel was used by the previous owner of the “donor” car. Haven’t there been metal shavings, impurities, dirt in the fuel system or not. Third – if the spare parts were stored in the scrapyard, they start to rust (also from “inside”)! In the scrapyards, nobody takes care that the fuel system is stored with fuel inside. Directly the opposite – the fuel is drained because it is money. 

Let’s see the diagnostics data. Here, how the diagnostics protocol looks like. You can judge by yourself how many lines from all lists are marked with an OK. For your convenience, incorrect values are marked with red.

As you see, almost all parameters (excluding only the engine’s temperature, the energy balance of the battery, and several more) are incorrect!

I will not burden you with INPA images, in which almost all values are marked as inappropriate.

Short summary

a. problems with the LP fuel pressure;

b. unreliable HPFP, with an unknown history and unknown origin;

c. serious problems with injectors (two of them area leaking strongly for a warm engine, third – averagely; for none of the injectors the atomization parameters are known, etc.);

d. completely damaged NOx system;

e. with a probability of 99%, the CO catalytic converters are damaged (in the idle, the temperature of the exhaust reaches more than 300 oC – the catalytic converters are simply burned);

f. problems with VANOS;

g. a damaged water pump;

h. unknown condition of the spark plugs, ignition coils;

i. unreliable Rail and LP pressure sensors;

j. problems with the air-tightness of the inlet manifold/CCV.

Here, how the estimate of the main repair works look:

Possibly, someone will argue – there is definitely no need to change everything here! You can save on something!

Let’s think – on replacement of which spare part we could save some money?

Can we skip the replacement of the CO catalytic converters? What will be the consequences? DME will turn off the Stratified charge. Will not measure injectors, the vibrations will start, an overload of the exhaust system. It will not be possible to normally drive the car; all exhaust probes will be destroyed, it will not be possible to pass the TI. Install cheap analogs of the CO catalytic converters? Unfortunately, there are no options for these specific engines.

Can we not replace the HPFP? Maybe several sensors can stay the same? Yes, you can try to spare 10% of the total estimate, but – if these worn-out spare parts fail, the CO catalytic converters and the probes in the exhaust will be destroyed. If the metal sheds from the damaged HPFP will get in the fuel system, all injectors will have to be replaced. 

Maybe not to replace any of the injectors? Maybe one of them (the one without indications of leaking) can still be used? Yes, we can try to spare 5% of the total estimate, but if this injector (without illusions, many years old, according to the complete condition of the car) will fail, the CO catalytic converters, probes in the exhaust, and even maybe DME will get damaged.

You can not spare the cheaper parts because the injectors and the spark plugs for these engines are manufactured only by the OEM manufacturers. It is not even worth thinking about HPFP “analogs”. The injection coils are not expensive (Bosch original). Save some money, installing non-OEM sensors? How much will you spare? 20 EUR? 25 EUR? Consequences? Expenses of EUR 1500 .. 2000. Is it worth the risk?

Unfortunately, there are no options to reduce the estimate. Most probably, it will only get higher. Without illusions – when the appropriate oil will be filled in the system (more liquid one filled by the seller of the car), the error message regarding lowered oil pressure will appear – a typical problem for these engines.

You can expect some more additional expenses – the oil and the filters of the automatic gearbox should be replaced. This service procedure will cost some EUR 500 more. 

I think this entry shows quite well how “cheap” could be 10+ years old BMW if it has not been maintained and repaired professionally.