coil pack

Firstly well done for your efforts. Plugs in cylinder heads are a dark-art, as one gets used to the feel vs how much effort you put on the wrench if they are coming out and not snap off! Especially with modern alloy cylinder heads, and slim plugs. For a beginner, a torque wrench is probably a wise move as its important not to do plugs up too tight...

On your 16v polo (from memory) the coil pack is at the end of the cylinder head, and has 4 red leads sat in grooves moulded in the plastic engine cover each running to a spark plug.

The coil pack is responsible for firing / sparking each plug at the right moment as instructed by the ECU.

With this arrangement of HT system, it's known as 'wasted spark', as actually 2 plugs fire simoultaneously (cylinders 1 and 4 are pairs, and 2 and 3)

Each lead will have a long boot which reaches down to the plug, and can be stubborn to remove. Never pull directly on the cable, but use a twisting motion on the top of the boot.

If you have the later 16v engine, then under the engine cover will be 4 individual coil packs, one for each cylinder. They sit atop of each plug and are bolted in place. Each has a 3 wire connector. Removing the coil pack upwards will reveal a long 'boot' which reaches down to the plug.

With this system, the ECU fires only the plug it needs to at the right moment.

The ECU is also able to actively monitor two additional things; a) firing voltage needed to fire the plug-varies according to engine load, speed and mixture ratio, and b) whether the cylinder actually fired or not.

Some ECU's can also monitor pinking conditions via the coil-on-plug system eg Saab's Trionic.

Hope this gives you some extra info.

Tim..

Once upon a time, a single large coil made the spark, this was delivered to the plugs via 4 HT leads. Nowadays, at least on most cars, every plug has it's own coil pack directly connected, therefore, there's no HT leads needed.

I thought it was finger-tight and a semi-grunt.

tishtash ( snipped-for-privacy@host.com) gurgled happily, sounding much like they were saying :

As others have said, the ECU fires a signal to a specific cylinder's coil pack when it's time for that cylinder to fire. That goes as a low-tension voltage down an 'ickle wire to the coil pack, which (since yours appears to be of the one-per-plug kind) then turns that into a high-tension current and fires the plug.

On a "traditional" car, the points (or ECU) would have fired an LT signal to the coil once per spark, no matter which cylinder. The coil turned that into a big fat HT voltage, bapped it down the king lead to the distributor, which pointed it towards the right cylinder. Hopefully.

Some cars use "wasted spark", where a double-ended coil fires both ends, one to each of a pair of cylinders simultaneously. One fires in the right place, one fires at 180deg (360deg, but let's not be picky) the wrong place in the cycle - as the burnt gas is being shoved out of the exhaust valve. It's not new, it's been around since at least the late 40s (with points).

just a tip, you shouldn't be using brake cleaner on a throttle body as you will remove the protective coating on them, the brake cleaner will strip it off, we use this at work

You wont go far wrong, if you tighten the plugs as tight as you can, using one hand gripping the plug socket T bar at the centre. Or, by screwing the plug in until you feel it bottom, then giving it a further half turn, so the plug washer is compressed, but not squashed completely.

I think you'll find that most ignition systems that monitor pinking, do it by means of an anti-knock sensor in the block. If pinking or knocking is sensed, it tells the ECU to retard the ignition. Sometimes referred to as a 'learning' system, as over a short period of the cars typical use, it will set the ignition timing to an optimum setting, and reset itself if a different grade of fuel is used. Mike.

..but obviously not if it's a taper-seat plug :-)

Indeed, but I think Tim was saying that *some* systems do it via the coil-on-plug module.

Chris

D'you know, I did not know that! I thought I knew cars but obviously I only know old cars.

Si - Shuffles off mumbling about 'letrics 'n 'tronics.

I think you will find that the first gen of knock control was via single or twin knock sensors, but the 2nd generation method of doing it is via the coil on plug.

Tim..

True. My mistake. I should have made it clear that the second method only applied to plugs with washers.

I don't know how such a system works, unless a knock sensor is built into the plug coil. Maybe someone can enlighten me. Mike.

Correct, but the leads are black on ours (OK, It's a Lupo, but same engine). Coil pack is on RH end stood in front of the car, leads clip into the engine cover as described. Plugs are quite a long way down.

First hit from Google for "saab trionic knock sensor":

Chris

Thanks for that post above, I saved it for future reference as its really good! Thanks for taking the time to give me that insight as its explained alot.

I have this morning taken the engine cover off, found 4 coil packs and removed them and the spark plugs are deep down in the cyclinder head. I'm not sure of the size of the spark plug socket I need so thats my next port of call to find the size and go to halfords. I think as its deep down I shall need an extention bar I have a 3" one but no sure if it'll reach. Gives me an excuse to buy a lonmger one may be useful one day for something else.

What I was wondering the boot that covers the plug, how would I put it back on? I didn't take it off today as I was just looking, is it a case of just pushing it down as far and hard as I can till I hear a click as it goes back on ? or feel for something any advice one that ?

Thanks

Thanks Chris. It is indeed. I did try googling for 'Saab knock sensor', before I asked my question, without results. I should have been more specific, but delving into Trionic a bit further, seems to indicate that it's a system unique to Saab. Mike.

On 2007-02-16, tishtash wrote: [...]

You just sort of drop it back on and do up the bolts. I am basing this advice on practical experience of only one car with coil packs so yours might be different.

"Refitting is the reverse procedure to removal" is the motto basically.