Polo 1.0 (6N) 16684 & 16688 Misfire Codes

[½cwt]

I've just picked up a cheap (yeah, usually a good reason...) 2000MY Polo 1.0 for my step-son to learn to drive/get road experience in.

Having replaced the battery so it actually starts I've got two sets of fault codes, 16684 and 16688 on the engine (random multiple mis-fires and cyl 4 mis-fire) I've changed cyl 4 plug lead for a known good one but still have the problem. It is an intermittent fault, usually under throttle applications between 1900 and 3000 rpm, plus idle is a bit lumpy occasionally. Where to look next?

The other set is 00290 and 00287, both for left rear wheel speed sensor. No ABS light at the moment, most info seems to be a good clean around the sensor as the best start.

Chris

[Guest 2]

Do these Ross-Tech links help?

16684/P0300/000768 - Ross-Tech Wiki (http://wiki.ross-tech.com/wiki/index.php/16684/P0300/000768)

16688/P0304/000772 - Ross-Tech Wiki (http://wiki.ross-tech.com/wiki/index.php/16688/P0304/000772)

00290 - Ross-Tech Wiki (http://wiki.ross-tech.com/wiki/index.php/00290)

00287 - Ross-Tech Wiki (http://wiki.ross-tech.com/wiki/index.php/00287)

[½cwt]

Thanks for these.

They give a range of possible faults on Ross-Tech and I'm trying not to throw parts at the problem. I guess a good check and clean up of the induction system would help, although with cyl 4 also identified and a plug lead change on that I'm looking at lack of spark or low compression in that cylinder, can't be fuel as its single point injection.

Chris

[SammoVWT]

It can be fuel with single point if your one injector is dirty. Its worth checking out - if you can check your fuel trim to see if you can figure out if its lean/rich or something else. Its quite handy to watch a few things on the log while the car is running.

A lot of my recent issues were down to wear&tear items, apart from my broken injector i had 3 gummy ones from the injectors opening to compensate for the failing cylinder. Made a mess of everything.

I changed, cap & rotor arm, coil, plugs & leads (3 times - cheap aftermarket parts made me cry), cts, thermostat and expansion tank cap and ran some wynns injector cleaner and carb cleaner to try to clean everything up short of pulling the intake manifold off.

Check the state of your breather, if its full of mayo, just clean it up - keep an eye (and ear) out for splits/vacuum leaks. The usual, start cheapest and what you can prove and work upwards.

[Doctle Odd]

Check for a burnt valve too, loads to do!

[½cwt]

Check for a burnt valve too, loads to do!

I guess that will mean a compression test?

[Doctle Odd]

I guess that will mean a compression test?

Yes :)

[½cwt]

Did a thorough clean up of throttle body, injectors and spark plugs, mis-fire still there but I can hear a clicking from the ignition pack when it misses. Might this be a clue?

[SammoVWT]

the clicking is a loose spark getting about somewhere most likley. If you can run the engine while its dark you may be able to see it if you look closely.

[½cwt]

So if I find that this lose spark is around the coil pack I guess it's the faulty part?

[SammoVWT]

I would say so, that means the insulation has broken down, and the easiest path for conductance is anywhere but where it's supposed to be. You might not always see this, is the problem worse when cold/damp? or warm?

Keep in mind that sometimes the sparks arent always easily visible, so its not a surefire - an indicator.

If when the car heats up its harder to start with the engine warm, or requires a few minutes before it will start then that sounds like the coil needing to cool down in order to operate "correctly".

I had one coil fail so spectacularly you could hear it arcing (and crackling an awful lot) out behind the dash when you were driving or starting the car sometimes. That got changed quick snap!

[½cwt]

After recharging battery (see other thread...!) got it started this evening and a nice little intermittent spark display going on low down behind the coil pack. Hopefully job done but I'll report back to confirm after fitting a new pack at the weekend.

Thanks to all for their help so far.

[½cwt]

Coil pack replaced, all now running well with no engine fault codes!

Again, thanks to all.