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Compression in cylinder 3 is insufficient.


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Greetings, I already posted a discussion about the occurrence of a misfire in cylinder 3. I have replaced the coil packs and spark plugs, however the misfiring issue persists. This morning, I had the vehicle undergo a compression test, during which the technician informed me that it failed since it did not maintain any pressure. What should I do next? The automobile has accumulated a mileage of 170,000 kilometres. As the second owner, I have personally had this automobile for many years, and around 80,000 miles have been driven on the road. Is it worthwhile for me to invest further funds in diagnosing the precise issue inside the engine, or what would be the optimal course of action for me to pursue at this point?

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Unless a cost-effective engine replacement can be found, it is unlikely to be financially viable to invest in a vehicle with 170,000 miles on the odometer. Despite the installation of a newer engine, the car's value remains insignificantly low, estimated at around 170,000 units of currency, or a mere fraction of its original worth. It has had a successful period... now it is time to bid goodbye. Disassembling your present motor is likely to be costlier than installing a pre-owned one, unless you possess the necessary expertise to do it yourself.

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While I generally agree with the most of your statement, it is important to note that the CLA is a comparatively contemporary vehicle and may still possess a considerable value of a few thousand pounds, despite its mileage. The most affordable options I have seen on AT are priced at £6,000 to £7,000, but they have accumulated 120,000 to 150,000 kilometres or have been declared as HPI write-offs. It is likely to have a value of about £4,000 to £5,000, depending on its condition.

If the other parts of the vehicle are in excellent condition, it may be worthwhile to consider fixing it. However, I would be inclined to sell it in its current state, with the misfire issue stated, since there may be individuals possessing the necessary skills, tools, and knowledge to potentially repair it well.

Compensating for another individual's time may be costly, and regardless of the approach you choose, the repair process will require a significant amount of manual work.

Incorporate the repair expenses into the current market value, estimated as about £2,000 to £3,000. Opting for a vehicle with lesser mileage might be advantageous, particularly if you anticipate driving a significant number of miles in the future.

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If I were in possession of the item in question... I would do a leak down test to identify the specific location where the pressure is being released. If the direction of movement is downwards, it indicates a malfunction in the piston or rings of cylinder number 3. This issue would need a costly repair, most likely including the removal of the engine.
If there is a leakage occurring beyond the valves, a potential solution might include removing the cylinder head and replacing the valves, which may be a cost-effective remedy.
However, it is crucial to determine the underlying reason of the failure, since failing to do so may result in its recurrence.

I would wager that the issue lies with the exhaust valves being damaged by heat. It is imperative to determine the cause of this problem before any repairs can be contemplated.
Which octane rating of gasoline is advised and which one was utilised?
Has it been reconfigured?
What was the level of oil consumption before the misfire became apparent?

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Alternatively, you may use an inexpensive borescope to visually inspect the area. I personally use a cost-effective borescope purchased from eBay, which is compatible with a free application on my smartphone. The investment has proven to be really beneficial and has yielded significant returns.

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Is there a remapping of Rice Krispies (snap, crackle, and pop)?


Did the OEM suggest using the original version without any modifications, and did the remapper advise using a higher octane fuel following the remap?


Is there a visible leak without any combustion?

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A decrease in cylinder compression may be attributed to either valve seat wear or valve gear failure, such as a broken valve spring. [The issue can be fixed, but it will likely require elevating the head.] If the engine has bore wear, piston ring fracture, or severe wear, repairing it would be uneconomical. Confirming this can be done using a Borescope, as previously indicated.

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