1.8T misfire problem

[green beard]

Hi all I'm looking for some help with this misfire on my 14 years young Octavia Estate SLXi engine code AGU. It has been there a few days and at first it ran ok when cold but now it is misfiring all the time.

 

I have swapped the plugs and switched the coil packs around and the problem is that cylinder number 2 is not getting the message to fire.

 

I have had this confirmed by my local mechanic today and he also checked compression on all 4 cylinders while he was at it, he says they are all slightly on the low side but it's nothing you wouldn't expect and there is certainly no major problem with the engine. Mileage is just short of 90k.

Also he inspected the wiring and sprayed some contact cleaner on there just to make sure.

 

There are no fault lights displayed and has been running fine right thru the rev range during my year of ownership (10k miles)

 

Do the wires to the coils come straight from the ECU or is there something else in between?

 

If it needs a new/working ECU does it have to come from a car with same engine code or will any do (for instance a VRS - might as well!)

[BrownBarge]

A vrs ecu wouldnt work.

Its a known problem that the wiring for the coilpacks can break down i think you can buy replacement loom just for the coilpacks. Might be wrong though. Its worth tracing the wiring back to get for breaks/damage

[green beard]

VRS ECU not work - OK I'll settle for just a car that works!

 

Ah ok that's great I'll check the wiring out.

 

This is going to sound a bit pathetic but could you tell me where the ECU lives?

I have just had a look and it is not under the bonnet like my old Fabia and pics of other cars I have seen!

 

Thanks.

[IulianE]

Hi all I'm looking for some help with this misfire on my 14 years young Octavia Estate SLXi engine code AGU. It has been there a few days and at first it ran ok when cold but now it is misfiring all the time.

 

I have swapped the plugs and switched the coil packs around and the problem is that cylinder number 2 is not getting the message to fire.

 

I have had this confirmed by my local mechanic today and he also checked compression on all 4 cylinders while he was at it, he says they are all slightly on the low side but it's nothing you wouldn't expect and there is certainly no major problem with the engine. Mileage is just short of 90k.

Also he inspected the wiring and sprayed some contact cleaner on there just to make sure.

 

There are no fault lights displayed and has been running fine right thru the rev range during my year of ownership (10k miles)

 

Do the wires to the coils come straight from the ECU or is there something else in between?

 

If it needs a new/working ECU does it have to come from a car with same engine code or will any do (for instance a VRS - might as well!)

 

My friend you need a new ignition module,the one on the air box

[green beard]

Well, I know where that is at least!

 

You sound very sure of that, can you explain a little more?

[IulianE]

we have different coilpack than the VRS,they have an external trigger wich is this module.

I have same engine AGU and had the same problem,so I'm not smart don't worry,I just had the same problem.In fact I'm quite stupid.

 

These modules like to get broken on the no2 cilinder,so was mine

Edited 8 March, 2014 by IulianE

[green beard]

That's exactly what I needed to hear!

 

It all makes sense now.

 

I don't know if you have seen Teflon Tom's Felicia build thread? He has put AGU in there and mentions mounting this Ignition Module on a large heat sink as they are prone to blowing up. Might be something for us to consider?

 

Thanks again.

[IulianE]

yes,it must be mounted with heatsink....mine failed because the heatsink was gone,engine was washed few times and consider the age of the car,I bet yours is the same.

[green beard]

I will have to look tomorrow.

 

Tom has mounted his at the back of the engine bay on a big heatsink from an old hifi amplifier I think.

It looks to be about 100mm x100mm 

 

EDIT: looks to be a bit smaller than stated and mounted on the wheelarch

[green beard]

The thread is in Skoda Classic Project Journals part of the forum.

[Turbo_Boss]

My friend you need a new ignition module,the one on the air box

 

IulianE is right! Your problem is the ignition module thats goes on the filter air box.

 

I suffer the same problem on my 2002 1.8T AGU engine and it was the ignition module.

 

Check this thread were they show you how to fix that part.  I fix it the same way.

 

http://uk-mkivs.net/topic/51078-repairing-bosch-4d0-905-351-icm-unit/

 

 

I will say that the problem why this part get damage is beacuse the thermo conductive paste between the back of the ignition module and the metal plate on the air filter get dry and this allow the part to overheated and this desolder one of the internal electrical contacts.

 

Just open the plastic case carefully and then just solder the baad contact.  It will be a pain in the ass to solder that thing because it will not want to get the solder.

 

You can read there my fix but I will repeat it here:

 

Here are some tips. The pin (connector) side is definitely solderable, as is the wire. The secret to the pin side is to remove all the heat sink gel completely from around it.

Then scratch the surface to clean it until it get like a gold color. Then put the soldering iron on. You need to use a hi wattage Soldering Iron. Keep it down for probably at least a minimum of a minute then try to apply solder to the pin. Once the pin takes the solder, move the wire into it.

As for the other side, the FET side, scratch the surface to clean it until it get like a gold color. Then again, apply a lot of heat.  Belive or not, with the help of a friend I use two 40 Watts soldering iron and leave it like a minute, then the wire got soldered.  After I finish, I push very hard the solder with a small screw driver and it don't move.

Then put black silicone around the edges and put again the plastic cover.

 

After you fix the part, MAKE SURE to sand both metal plates (the back of the ignition module and the metal plate were the Ign Module goes and then put thermo conductive paste.

 

Good luck and make sure to take some photos to post them here.

 

Isaac

Edited 9 March, 2014 by Turbo_Boss

[IulianE]

I didn't know you can fix this,I bought a new module and wasn't cheap at all.

[green beard]

OK cool, I'm going to have a look at fixing this myself.

 

Found soldering iron - 60w!

 

I'll take some pics and if it all works out I'll try and get them up here.

[Turbo_Boss]

OK cool, I'm going to have a look at fixing this myself.

 

Found soldering iron - 60w!

 

I'll take some pics and if it all works out I'll try and get them up here.

 

Just be carefull opening the plastic case. Take your time with a X-Acto or similar sharp blade tool. Be carefull if you introduce a small screwdriver to pry the top of the plastic case. If you introduce it to much, you will touch/damage the circuit board.

 

Again, take your time and be patience with that plastic top cover

 

Good luck,

 

Isaac

[Turbo_Boss]

I didn't know you can fix this,I bought a new module and wasn't cheap at all.

 

I fill your pain! The Skoda dealer was asking US$ 450.oo for that part. So, I make a search on the net to see if I can buy it on ebay for less and found the tread on how to fix it.

 

Isaac

[green beard]

Thanks for the take care warning Turbo_Boss, sadly I got stuck into this straight after my last post and have done everything you have said to avoid!

 

But, it's definitely the problem - I found the broken wire - snapped off at the edge of the pin, you could see the other bit of wire still fixed in place - I tried to mend it but after an hour of trying to solder it back on I have given up - thought I had it a couple of times but was a dry joint or similar. As you have said, it is possible but not by my fair hand.

 

With my trying for so long the wire was getting very fragile and I was afraid it would snap off from the chip type thing it's wired up to.

Combined with the plastic case being a long way from it's original seating I decided to get a new one. Thankfully a good quality Beru replacement is less than £70 so compared to your $450 not so bad? 

 

I did take some pics so I will try and get them up so people can see what they're dealing with?

[Turbo_Boss]

Thanks for the take care warning Turbo_Boss, sadly I got stuck into this straight after my last post and have done everything you have said to avoid!

 

But, it's definitely the problem - I found the broken wire - snapped off at the edge of the pin, you could see the other bit of wire still fixed in place - I tried to mend it but after an hour of trying to solder it back on I have given up - thought I had it a couple of times but was a dry joint or similar. As you have said, it is possible but not by my fair hand.

 

With my trying for so long the wire was getting very fragile and I was afraid it would snap off from the chip type thing it's wired up to.

Combined with the plastic case being a long way from it's original seating I decided to get a new one. Thankfully a good quality Beru replacement is less than £70 so compared to your $450 not so bad? 

 

I did take some pics so I will try and get them up so people can see what they're dealing with?

 

I am sorry to hear you cant solder the wire.................. Well £70 is not that bad.

 

Solder that part is a PITA! That metal part is like plated and dont want to take the solder. I was with a friend and we put 2 40 Watts soldering iron and leave it like a minute, then the wire got soldered. Its look like the metal part need to get very hot in order to acept the solder.

 

When installing the new Ignition module, sand the metal plate on the air filter and make sure to remove any old dry paste.....Just make sure the metal surfase is flat and clean in order that the plate touch 100% the back of the ignition module.

 

Keep in mind that the plate in the air filter is a heat disipation aid to help cool the ignition module.

 

Also, MAKE SURE to put thermo conductive paste on both parts......... This will help on a better heat tranfer in cooling the Ign Module........ You can get this paste in any electronic or computer parts place.

 

Good luck,

 

Isaac

Edited 9 March, 2014 by Turbo_Boss

[IulianE]

I'm glad you solve it.....by the way,you said at the begining you had a compression test and it was a bit low....what were the values?

[green beard]

I don't know but I still owe him money for having a look so will ask when I go pay him - also I will take the ICM and show him how my car works LOL!

 

Are you interested to know what is considered to be a low reading?

[IulianE]

yes,I want to do a compression test myself and want to know the figures of another AGU engine older than 10 years like mine

Edited 9 March, 2014 by IulianE

[green beard]

 

1 this is where the unit lives on the back of the airbox

2 close up

3 I disconnected the ICM, MAF and the air hose clip - 2 screws on airbox and the lid comes off

4 this the heatsink for the Ignition Control Module viewed from inside airbox lid

5 I used a small terminal screwdriver but a knife would probably be better, use caution here as inside is very fragile as you will see

6 inside the unit - hopefully you can see the broken wire on the second chip - you need to identify which wire is the problem and try and solder it back on to the pin - good luck with that - I couldn't do it but others have.

[green beard]

Ignition Module replaced with new and been running fine for the last few days 

 

Regarding compression test, mechanic could not recall the exact figure but told me 150psi is the norm and all 4 cylinders were slightly lower than that - he says nothing to worry about - no reconditioning of the head needed - normal for the mileage, 90k miles.

Probably piston rings?

Does anyone else have any views on that?

[IulianE]

150 PSI is at the edge...after some research I found that good values are between 148-203 PSI

[green beard]

150 PSI is at the edge...after some research I found that good values are between 148-203 PSI

 

Ah, right so it is on the low side like he said but still ok. I'm not rushing out to buy new piston rings just yet.

How does yours compare, have you tested it yet?

[IulianE]

No I haven't test it yet....