Erratic Idle

[morph3]

Hi, i have a Renault Megane 1.4 16 valve Fidji 52 plate and im sure this is a MK1 as its the older shape.
My car had an erratic idle and we put it on a computer ata garage and it only came up with a faulty Lambda sensor, so i changed the sensor and it still idles erratically, so the next thing i tryed was cleaning the idle control valve out which i was advised to do by a Renault dealership, that did not help so i changed the air filter too.

My car is still idling erratically, is there anything else i should check, bare in mind i have limited knowledge on car engines..... Much appreciate any help

[scatz]

Aye, Mk1 Phase 2

Perhaps a coil or two? They are the most common failure on Renaults it appears and will cause erratic idling. However, there are many other things which could also cause the same symptoms!

	Ignition Coils Ignition Coils An ignition coil (also called a spark coil) is an induction coil in an automobile's ignition system which transforms a storage battery's 12 volts to the thousands of volts needed to spark the spark plugs. This specific form of the autotransformer, together with the contact breaker, converts low voltage from a battery into the high voltage required by spark plugs in an internal combustion engine. In older vehicles a single (large) coil would serve all the spark plugs via the ignition distributor. In modern systems, the distributor is omitted and ignition is instead electronically controlled. Much smaller coils are used with one coil for each spark plug or one coil serving two spark plugs (so two coils in a four-cylinder car). These coils may be remote-mounted or they may be placed on top of the spark plug (coil-on-plug or Direct Ignition). Where one coil serves two spark plugs (in two cylinders), it is through the "wasted spark" system. In this arrangement the coil generates two sparks per cycle to both the cylinders. The fuel in the cylinder that is nearing the end of its compression stroke is ignited, whereas the spark in its companion that is nearing the end of its exhaust stroke has no effect. The wasted spark system is more reliable than a single coil system with a distributor and cheaper than coil-on-plug. Where the coils are remote mounted they may all be contained in a single moulded block with multiple high-tension terminals. This is commonly called a coil-pack.

[morph3]

Thnks scatz i will try the coils, do you think i should change the spark plugs also and were would i locate the ignition coils, are they easy enough for an amature to replace?

	Ignition Coils Ignition Coils An ignition coil (also called a spark coil) is an induction coil in an automobile's ignition system which transforms a storage battery's 12 volts to the thousands of volts needed to spark the spark plugs. This specific form of the autotransformer, together with the contact breaker, converts low voltage from a battery into the high voltage required by spark plugs in an internal combustion engine. In older vehicles a single (large) coil would serve all the spark plugs via the ignition distributor. In modern systems, the distributor is omitted and ignition is instead electronically controlled. Much smaller coils are used with one coil for each spark plug or one coil serving two spark plugs (so two coils in a four-cylinder car). These coils may be remote-mounted or they may be placed on top of the spark plug (coil-on-plug or Direct Ignition). Where one coil serves two spark plugs (in two cylinders), it is through the "wasted spark" system. In this arrangement the coil generates two sparks per cycle to both the cylinders. The fuel in the cylinder that is nearing the end of its compression stroke is ignited, whereas the spark in its companion that is nearing the end of its exhaust stroke has no effect. The wasted spark system is more reliable than a single coil system with a distributor and cheaper than coil-on-plug. Where the coils are remote mounted they may all be contained in a single moulded block with multiple high-tension terminals. This is commonly called a coil-pack.

[scatz]

Coils are directly above the spark plugs, you need to pull them off the plugs to remove the plugs so you can't miss them

You may as well check the spark plugs whilst you are there to see if they give any clue as to which cylinder may be the problem....if indeed it is the problem! Check the gap and condition obviously!

Another 'quick' check is to pull each coil off (or at least unplug the electrical connection to the coil) one at a time to see if there is any change to the engine! If you pull a good one then you should get a miss fire, if you pull a bad one then you'll probably notice no change at all to the engine note/firing! Don't leave anything unplugged whilst the engines running for too long as you may cause damage

	Ignition Coils Ignition Coils An ignition coil (also called a spark coil) is an induction coil in an automobile's ignition system which transforms a storage battery's 12 volts to the thousands of volts needed to spark the spark plugs. This specific form of the autotransformer, together with the contact breaker, converts low voltage from a battery into the high voltage required by spark plugs in an internal combustion engine. In older vehicles a single (large) coil would serve all the spark plugs via the ignition distributor. In modern systems, the distributor is omitted and ignition is instead electronically controlled. Much smaller coils are used with one coil for each spark plug or one coil serving two spark plugs (so two coils in a four-cylinder car). These coils may be remote-mounted or they may be placed on top of the spark plug (coil-on-plug or Direct Ignition). Where one coil serves two spark plugs (in two cylinders), it is through the "wasted spark" system. In this arrangement the coil generates two sparks per cycle to both the cylinders. The fuel in the cylinder that is nearing the end of its compression stroke is ignited, whereas the spark in its companion that is nearing the end of its exhaust stroke has no effect. The wasted spark system is more reliable than a single coil system with a distributor and cheaper than coil-on-plug. Where the coils are remote mounted they may all be contained in a single moulded block with multiple high-tension terminals. This is commonly called a coil-pack.

[morph3]

I will try that tonight and let you know the outcome tommorow, thanks for the help