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Discussion Starter · #1 · (Edited)
Hi folks

My Hyundai Matrix CRDI 1.5 with 3 cylinders started with rough idle a little time ago, i try to describe the problem:
1. Leave the car overnight so it gets completely cold
2. Start the engine, it starts immediately, but pressing the gas pedal have absolutely no response. The engine runs (rough) and pressing the gas pedal or not does not make any change at all.
3. Around 30 seconds later, it starts responding to the gas pedal and 5 seconds later i responds as it should. (however with smoke and rough engine)
4. White smoke is sourronding the car, and i drive ahead, when car is running idle, the engine vibrates very much, you can really feel it in the cabin, after around 5 minutes the car is just super, and runs perfectly, diesel consumption is normal, idle is fine, acceleration is fine!
5. The car does not leak either oil or coolant at all.
6. Maybe the idle is a little rough when the car is hot, but maybe that is just paranoia, its much, much better with a hot engine. (i think maybe it has always been a little rough, also its a 3 cylinder so pretty normal i think)

What i have done, but with no effect.
1. Read out error code, it complained about a faulty mass flow sensor, so i replaced that. The car runs a bit smoother, but the idle problem is still the same.
2. Changed gas filter and replaced oil.
3. Replaced the diesel fuel filter.
4. Added a bottle of redex cleaning liquid to the gas tank and drove away on the highway at 140 km/h for a long time.
5. Read out error codes, no problems reported!
6. Read out temperature sensor, it seems ok, it follows the temperature as it should (i had an idea that the sensor was giving a valid but too high temperature when cold).

Anyone familiar with a problem like this? Where should i start?

I hope someone recognizes that it cannot respond to the gas pedal when cold, and runs perfectly when hot.

Regards Jens from Denmark
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