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Unstable engine operation at idle


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I own a Kia Picanto 1.1 G4HG with a damaged cylinder head. I purchased a new bare cylinder head and installed it. Additionally, I replaced the valves, crank sensor, cam sensor, coil pack, spark plugs, and spark plug leads.

The vehicle is now experiencing a decrease in power and the exhaust manifold sometimes becomes red-hot after idling for a period of time. Additionally, it is encountering difficulties in increasing its revolutions per minute (RPM) and is exhibiting backfiring and vibrations via the exhaust system. There seems to be an excessive amount of fuel flowing through the intake, causing the engine to initially operate smoothly for a brief period before encountering difficulties maintaining a stable idle.

Does anybody have a notion as to what it may be? I am now experiencing confusion and uncertainty.

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In my opinion, it may be described as a very lean fuel mixture, which is the reason for its high temperature.

I would suggest inspecting the manifold for any potential intake air leaks.

Observe whether a plug appears much whiter in comparison to the rest.

Apply WD40 to the whole intake manifold while the engine is running.
The location of the leak may be identified by observing any increase in engine speed or rapid variations in engine speed.

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Indeed, I suggest using a spray substance in the vicinity of the input manifold.

If you suspect the presence of a leak, there is a rapid method available to confirm its existence.

Let's start with the simple tasks...

If the system was running low before, I would anticipate the presence of a fault code and an illuminated Engine Malfunction Light (EML).

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There appears to be an issue with the fuel/air mixture. It is possible that the fuel injection system is obstructed or that the fuel line is insufficiently sized or bent. Another possibility is that the fuel filter or fuel pump is running low, or that the air supply is restricted due to a clogged intake, filter, or poorly connected hoses. In a worst-case scenario, the computer controlling the engine may be malfunctioning, despite the absence of any error indications. To troubleshoot this, it wou
I would thoroughly cleanse the engine's interior by using a specific cleaning under the fuel pump and then flushing it at a professional workshop. Furthermore, while activating the air-conditioning system, the engine's revolutions should increase, not decrease. It is possible that the oil inside the air-conditioning system has leaked, causing the system to malfunction.

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The air conditioning system is operating without any restrictions. However, the previous technician who serviced the vehicle applied excessive torque to the head bolts, resulting in a broken head. Consequently, I replaced the head. Prior to this issue, the car was functioning well, with the exception of piston 3, which had oil leakage onto the spark plug due to the damaged head.

Regrettably, I do not believe that any of the current tasks being performed would have an impact on the computer. Moreover, I do not have any acquaintances who own a computer that I might borrow for the purpose of conducting a test to confirm my hypothesis.

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The vehicle has travelled a distance of 300,000 km. However, when I detach the hose from the PCV valve, the engine's idle performance deteriorates. I have already cleaned the valve, and there are indications that it is functioning properly.

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Apologies, I am now unable to generate any further ideas. If I were able to, I would anticipate receiving an electronic message on the dashboard.

In order for the exhaust manifold to emit a glowing effect, it requires the presence of very hot gases, which is often achieved in engines that are well tuned.

Furthermore, this would occur at an exceedingly high revolutions per minute (RPM) for extended periods of operation.

Your situation is peculiar since you do not have an air intake leak.

Your hypothesis about the fuel not reaching the injection side may be valid. However, it is reasonable to assume that the Engine Management System (EMS) would detect and indicate this issue. Will the fuel pressure be low?

I recommend doing a comprehensive diagnostic on this vehicle using a rolling road, or alternatively, considering its disposal.

I would have likely completed the task by now.

Apologies, but sometimes it is more advantageous for one's mental well-being.

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I am considering abandoning the project since I have never seen a situation like this before. Initially, I suspected that the exhaust may be obstructed by the cat, causing the issue. To test this hypothesis, we replaced the exhaust pipe with a decatted one, but the problem persisted.

Perhaps the issue might be attributed to the valve timing.

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I considered the possibility that the issue may be attributed to insufficient or improper lapping of the intake valves, resulting in a combustion failure of the fuel-air combination.

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