Very rough idle on my 1994 mazda 323

[Damien Hill]

Hi There,
So does the temperature rise when this happens? or do you mean this is where it normally sits

As for the rough idle, because it is an older car it could be a number of things… Over time the engine mounts wear and you will notice more vibration than normal. But if the temperature is changing with the symptom it could be different. I would start by checking the basics… Spark plugs, leads, distributor cap etc. Its amazing how much changing something as simple as spark plugs can be.

You mention the car feels like it is going to stall, a couple of things you can try is (if the car has it) turning on the Air Conditioning or anything with a decent electrical load and seeing if the idle rises or stays the same.

Keep us posted.

Topic

[celticbhoy]

Hi D.Hill,

The spark plugs, leads, and cap are all 6000 km’s old, but I didn’t even think about the mounts so i’ll look into that.

The temperature rises and stays at the 60-70% range so that is where it normally stays.

I have a toggle switch connected to the cooling fan because I wanted to run the fan constantly. Apparently what’s common for the 94 323’s is that the cooling fan comes on for 10 seconds every so often and then stops, but I wanted it to run continuously. When I flip the switch, the idles dips from 400-500 down to 300 for a brief moment and then goes back to 400-500.

[EricTheCarGuy]

Quoted From D.Hill:
Hi There,
So does the temperature rise when this happens? or do you mean this is where it normally sits

As for the rough idle, because it is an older car it could be a number of things… Over time the engine mounts wear and you will notice more vibration than normal. But if the temperature is changing with the symptom it could be different. I would start by checking the basics… Spark plugs, leads, distributor cap etc. Its amazing how much changing something as simple as spark plugs can be.

You mention the car feels like it is going to stall, a couple of things you can try is (if the car has it) turning on the Air Conditioning or anything with a decent electrical load and seeing if the idle rises or stays the same.

Keep us posted.

Great post!

I’ll add that a hard wired cooling fan is not really the best option in my opinion as a fan circuit is a high amp circuit and as a result would put a big load on the electrical system which would also put a load on the engine. When the vehicle controls the fan circuit it automatically bumps the idle to compensate for the load, if the computer doesn’t know why there’s suddenly an electrical load it can foul up the idle circuit.

You might also consider cleaning the MAF sensor as this can clean up the idle a great deal and it’s a simple low cost solution.

[Author]

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