Idling trouble with a secondhand purchase

Strange liquids and strong vibrations can\'t be a good thing if it\'s a car we\'re talking about
by Ferman Lao | Oct 19, 2009

Hi Ferman,

Good day!

This is the second time I have to inquire about a motoring problem. Thanks for answering my first query.

I recently bought a secondhand 1991 Lancer GTi (4g15) from a fellow club member. I noticed these strange observations:

1. So much resistance from the engine at startup

2. There is so much vibrations inside. I have set the idle RPM at 800 and luckily the vibrations are reduced but I can still feel it especially when the aircon is on

3. The spark plug on cylinder 2 is wet--not by oil but by what I think is water. When I removed it and tried to use a lighter to light it up, the liquid didn\'t burn

4. I have bad fuel consumption (5km per liter), and I\'m using higher octane gasoline. My research says if you have a low-compression engine, just settle for a premium grade--is this true?


5. rpm needle goes up and down even when the aircon is on. The previous owner installed an actuator coming from a carb engine as servo replacement

And lastly, how do you adjust the air fuel mixture of an EFI Engine? Is this possible?

I apologize for asking too many questions but I really appreciate your help. I hope you have a shop in the south as well so I can easily bring my car.

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Thanks and more power to Top Gear Philippines. By the way, it\'s really hard to find back issues nowadays!



Hi Francis,

Most of your problem comes from what sounds like a faulty or non-functioning idle control system (of which a part of it is the servo motor).

During startup from cold most engines will automatically go up to 1500rpm for a minute or so to enable it to get to operating temperatures quickly. If it doesn\'t do so and you have the symptoms you described, then you need to get it addressed properly for you to get to a real solution.


The vibration you encounter with the aircon on is also connected to your idle control problem.

When the aircon compressor is on, most engines go up a few hundred rpm to compensate for the added load. You don\'t normally see this as the control system will always keep idle at about 750rpm to 850rpm for most vehicles.

The reason why your rpm needle is going up and down is because the engine isn\'t compensating for the load and is struggling to maintain idle rpm. While there is a way to adjust air fuel mixture on your car I wouldn\'t recommend it as doing so without proper tools will do more harm than good.

About your moist plug, it would be hard to say what the liquid is without actually seeing it. But given the multitude of problems you seem to have with your engine, your best option is to bring it to a qualified service shop and have everything brought back up to specification.


Best regards,

Ferman Lao

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