Multiple errors logged by misfiring engine

[andrewboom]

I started my 51 plate Skoda Octavia 2.0 8v auto for the first time in about 10 days yesterday, and encountered really bad rumbling from the engine.

The check engine light was lit. I have mangaed to get the following error codes from the car:

16645 Cyl.1 Injector Circuit Low Input/Short to ground
16648 Cyl.2 Injector Circuit Low Input/Short to ground
16651 Cyl.3 Injector Circuit Low Input/Short to ground
16654 Cyl.4 Injector Circuit Low Input/Short to ground
16684 Random/Multiple Cylinder Misfire Detected
16685 Cyl.1 Misfire Detected
16688 Cyl.4 Misfire Detected
17833 Tank Vent.Valve Short to Ground
17843 Sec.Air Inj.Sys.Pump Relay Circ. Short to ground

We have had some heavy rain during the last few days. Do you think something has got wet and shorted out? Any idea what I should check\change first?

Or does anyone know a good auto electrician in the Medway\Kent area who I can call out?

Thanks in advance

[Steve_D]

I would start by clearing down all the codes and start again. If the same codes come up see if you can at least get the car up to temperature then clear them down again.

Steve

[Simon says]

I have seen cars with a low battery/slow cranking making the car liable to flood easier,this can also cause spurious errors and tripping the fault light,as mentioned already get the codes cleared then see what pops up.

[adyady1066]

I'd check the pressure from the fuel pump if it was mine. The Octavia is based off the old VW Passat / Golf which were prone to failing fuel lift pumps in the tank. If you can't get a meter on it at least check that you have pressure at the rail. There should be a bleed off valve that looks like a tyre valve. The injectors will fail if the pressure is not regulated causing some of the fault codes that you listed and the vent valve will give false readings if the flow of fuel varies.

Like the other guys said, wipe the codes and start again. ANY misfire will always come up on the ECU as a random misfire but it seems like it's from the fuel not the sparks. Although check to see if it has a dry coil pack at the front of the engine. They were reknowned for cracking and caused random misfires. You'll see the usual crack in it and signs of smoke damage. The terminals on the coil pack are prone to rusting too. Worth taking the leads off one by one and checking that too. It's usually something basic with the VAG motors.

Find the engine code on the chassis plate and search for common faults on Google too. That always throws up random faults that you'd never believe possible. Hope it helps.

[anonymous-user]

Firstly, i would only listen to people who actually know what they are talking about!

The codes you have set are "electrical" check codes, they do not relate to things like fuel flow/pressure etc. What the ecu is telling you is that on your injectors and other sensors it has detected that the power feed is shorted to chassis ground!. (it checks for the correct voltage and current flow on it's IO lines, and in this case has decided that there is zero volts (or close to that) on some IO.

This would suggest 3 possible things:

1) some fault in the wiring loom or connectors
2) a failed power supply wire (or possibly blown fuse)
3) a failed Ecu (unlikely, unless it is full of water!)

I'd start with some basic wiring continuity checks first myself.......


(the misfire codes are to be expected as a result of inproper injector operation)

[andrewboom]

Really pleased with all the help, thanks people.

Will report back when I get some daylight to check on the car.

[andrewboom]

I could not see any damaged wiring or loose connections, but to be honest I'm not 100% on what I was looking for. I would not know where to start with wiring continuity checks. I do own a multimeter but don't know where to start.

I cleaned up the battery terminals and wiggled all the electrical connections I could see, but found nothing loose.

I then cleaned down the errors and went for a drive. The vibration did not appear as bad as before, but the car was down on power, and the check engine light quickly started flashing before I got to the end of my road.

I read the error codes and got:

16684 Random/Multiple Cylinder Misfire Detected
16688 Cyl.4 Misfire Detected

No idea why I have less errors. Should I clear down again and go for a longer drive?

[stevieturbo]

andrewboom said:

I could not see any damaged wiring or loose connections, but to be honest I'm not 100% on what I was looking for. I would not know where to start with wiring continuity checks. I do own a multimeter but don't know where to start.

I cleaned up the battery terminals and wiggled all the electrical connections I could see, but found nothing loose.

I then cleaned down the errors and went for a drive. The vibration did not appear as bad as before, but the car was down on power, and the check engine light quickly started flashing before I got to the end of my road.

I read the error codes and got:

16684 Random/Multiple Cylinder Misfire Detected
16688 Cyl.4 Misfire Detected

No idea why I have less errors. Should I clear down again and go for a longer drive?

When you say "vibration" I can only assume you mean the car is not running on all 4 cylinders. So no, clearing codes and driving further is not going to fix it.

The ecu is indicating a problem may lie on cylinder 4, so it would seem sensible to at least check the plug is ok and that it does have a decent spark.

But of course just because the ecu reports something, doesnt mean it's always correct.

[anonymous-user]

stevieturbo said:

andrewboom said:

I could not see any damaged wiring or loose connections, but to be honest I'm not 100% on what I was looking for. I would not know where to start with wiring continuity checks. I do own a multimeter but don't know where to start.

I cleaned up the battery terminals and wiggled all the electrical connections I could see, but found nothing loose.

I then cleaned down the errors and went for a drive. The vibration did not appear as bad as before, but the car was down on power, and the check engine light quickly started flashing before I got to the end of my road.

I read the error codes and got:

16684 Random/Multiple Cylinder Misfire Detected
16688 Cyl.4 Misfire Detected

No idea why I have less errors. Should I clear down again and go for a longer drive?

When you say "vibration" I can only assume you mean the car is not running on all 4 cylinders. So no, clearing codes and driving further is not going to fix it.

The ecu is indicating a problem may lie on cylinder 4, so it would seem sensible to at least check the plug is ok and that it does have a decent spark.

But of course just because the ecu reports something, doesnt mean it's always correct.

A 1Hz flashing MIL indicates that the ecu has detected a currently existing misfire situtation. One that is bad enough to effect engine performance and emissions (and possibly damage the catalyst)

That would tie up with the codes logged.

Simple easy tests you can do is to swap components form cylinder to cylinder and see if the misfire "moves" with the component. This is an effective way of tracking the issue (ie move coil pack from 4 to 2, clear codes, drive car (carefully, not at high load/rpm) and see if the misfire is now picked up on Cyl2. If the misfire moves then you have your dodgey component, if it doesn't then try moving other things like spark plugs, injectors etc. if it never moves it is likely to be a wiring harness or powersupply issue

[andrewboom]

I did not think driving further would clear the problem, just that it might show up the errors that did not appear again after a cleared the errors.

I think I only have the one coil pack, but I will try swapping the HT leads, and checking the spark plugs.

[adyady1066]

I've lost count on how many coil packs I've replaced and as I said before in a previous text, start with the basics and don't rely too heavily on computer diagnosis. Is there fuel getting through at pressure and have you tried removing them and turning it over to check if they're injecting? If so how good is the spark? Is the spark jumping across at the coil pack and causing a random misfire? If you start there with basic fault diagnosis and get no answers you can then start looking at plug leads etc. For less than £10 you can buy some spark plug testers which can show you it's firing and sometimes whether it's missing a spark. Try turning it over in the dark and see if there's a spark in the engine bay. If there is a spark at the coil pack, don't touch it while it's running though if it is. (you may well get an unwanted hairstyle)

[andrewboom]

I'm keeping my eye on a new coil pack on ebay. I have a mobile mechanic (VAG trained) coming out on Saturday.

[adyady1066]

Hope it goes well for you. Like i say, having worked with many VAG motors you get to know the sometimes overlooked obvious and half the time the scanners tell you the fault and not the cure. It's ok saying there's a misfire on cylinder 4 for example, but the answer doesn't mean there's automatically a problem at the engine. For example: A customer took his 307 Pug to Peugeot 3 times, paying each time for a diagnostic. The first time they did nothing and still charged, the third time they told him the egr pipe was blocked and the emissions were all over the place as a result. What they didn't mention is WHY. After poking around with it for 20 minutes I diagnosed a faulty air mass meter. We changed it and it now goes like the clappers again. Fault finding is ok, but you need to look at why the fault is there and what could cause it.

Like with your car, there could be a multitude of faults but generally speaking, cars don't suddenly have loads of issues all at the same time unless the ECU is showing faulty or bad earthing in the car itself causing the ECU to go haywire. Normally they are all linked to one, sometimes two faults caused by the same part failing.

Let us know what the fault was in the end if you manage to fix it. I'd be interested for future knowledge if it was something more sinister.

Ady

[andrewboom]

All fixed.

Karl a mobile mechanic from Tech Auto fixed the problem this morning.

http://www.freeindex.co.uk/profile(techauto-vehicl...

He replaced the HT leads and plugs. When he removed the secondry air pump for better access, you could see the leads from the 4th cylinder was split and emitting sparks into the engine bay. The other leads where fairly worn out as well.

I have an oil leak from the breather\oil cap which I need to get fixed. The leak has left the engine bay damp with gunky oil. The car is now running very well, the best it has for a while. Not bad for a 126k old 8v engine. Hopefully it has lots of life left in it.

I can't recommend Karl enough. Really good service. Only £35 for the call out, and no pressure to let him fix it, onmce the problem was found.

[adyady1066]

So it was in the leads after all. As I said before, they were worth checking one by one as it's normally something basic with the VAG. But then, what would I know? I've just worked on them for 20 years?! LOL

Glad you got it fixed and thanks for letting us know what the outcome was.