Having sorted out the overheating of my recently purchased 98 Felly 1.3 MPI, the next problem was that of a misfire.

 

When I bought the car it was very rough at low revs upon starting.  It cleared after warming up and ran fine for the 360 mile trip home, despite wet conditions.

 

On my first trip after solving an overheating problem,  the car stuttered and misfired, sometimes like it was running on 3 cylinders.  It was a wet night with a fair bit of surface water.

 

Thinking the coil pack may be iffy, I ordered a pattern part from EuroCar parts as well as a set of plugs.  While waiting for those to arrive, I thought it would do no harm to clean the throttle body.

 

So I cleaned it with cotton buds, some 'muc-off' degreaser, wd-40 and microfibre cloth. I didn't take it off and I didn't spray loads of stuff into the throat.

 

Afterwards the car tickover was higher (1000 rpm) and if the accelerator was pressed, the revs would 'hang' at 2000 rpm.  I read all the Briskoda posts and tried the following:

 

• disconnected the battery for a few hours, reconnected battery, left ignition on for 30 secs, took for a long drive.  No change. No adaptation.
• carefully cleaned MAP sensor. No change.
• bought a VAG KKL lead from ebay, cleared fault codes using VCDS lite, then the whole battery disconnect thing. No change.
• downloaded MotorDiag 1.53 but could not get it to communicate with the car.  The software always showed "port not ready".

 

At this point I was considering buying a licence (99 USD) for VCDS in order to do the TBA.  Previous Bri-Skoda posters had claimed that VCDS lite could not be used for TBA.  This had apparently been confirmed by Ross-Tech.  Other users seemed to have had success.  I contacted Ross-Tech and someone called Olga reassured me that VCDS lite could be used for TBA. What was the truth?  Luckily I didn't have to fork out 100 dollars to find out.

 

What I did was find an older version of MotorDiag (1.51) which was in Czech.  I found that this actually could 'see' the car (interface OK vs Port not ready).  I went through the Factory Reset wizard but it would crash out after 6 or 7% of the reset process.  I tried this several times.  I went back to version 1.53 (english) which then actually worked.  Incredibly it went up to 100% of the reset process.  You then have to turn ignition on/off, take out and put back a fuse.  At the the end of the process MotorDiag does suggest using VCDS to do the TBA(!).  However, on starting the car the tickover was back to a steady 700 rpm and the 'rev-hang' was gone. Success!

 

Conclusions.  Motordiag is extremely flaky, but can work and is free.  Registered and activated VCDS may or may not work, but is an option for the future.  

 

It's worth pointing out that the cheapo cable needs a driver for it to work.  The driver on the CD did not work but I did get one off the internet that did.  You do have to go into device manager etc to check the COM port number (3 in my case).  I tried fiddling around with port settings but this did no good when trying to get Motordiag to work at first.

 

That's not quite the end of the story.  My cheap new coil pack (HAAS brand) was installed but the skoda wiring plug doesn't fit it very well and it could easily just fall out (it doesn't clip in).  I've cable tied it in place, but I might have to find a better solution.  

 

Since yesterday it's been dry, I've done 20 or 30 miles and no misfire.  However ... the car does tend to Kangaroo on the over-run.  I.e; when running with the accelerator closed in, say, 3rd or 4th gear.  I never noticed this before on this car or my other Felicia.  I wonder if there is some change to the fueling related to the TBA that has caused this?  From the forums it seems that virtually everything could be a cause. From plugs to lamda sensors.  My first step will be to put the old coil pack back on and see if that changes anything. One change at a time should be the golden rule!

 

Hope this info is useful to fellow owners.

 

Gary

Exactly as I thought. All of a sudden, right after the overheating episode, the engine started to misfire. Is it just a coincidence? I think not.

Then you started to do maintenance and replace parts without having any evidence. No diagnosis whatsoever.

 

Let's make this topic interactive. What should Gary do next?

I know all these symptoms. 

Motordiag will benefit if Windows runs in safe mode so it's port doesn't get interrupted. 

I suppose you were getting an error going along the lines of lost bytes. 

Motordiag is enough and you do not need to reset though vcds. 

The car will self learn its values. 

Also the wd40 you sprayed ended up on the IAT sensor so clean it as well. 

The kangarooing problem occurs when 3 factors are combined. 

Not accurate crank sensor bad coils and plugs. 

But most importantly a random error in the ecu eeprom. 

My felly experiences low idle due to this issue. 

It also experienced kangarooing. 

What I did and it went away for some time was. 

Reset using motordiag then change crank sensor. 

With clean sensors and boom it was running perfect. 

I am afraid something along those lines is happening with you ecu as well. 

You can't do anything about it. 

But let's not rule out the possibility of the head gasket saying goodbye. 

Felicias should not be allowed to go beyond the white line before the red zone if they exceed this line then 90% is game over for the head gasket. 

 

Thanks for all of your feedback.  Regarding the head gasket, I'll just need to wait and see.  

 

Oddly enough, it didn't start to misfire right after the overheating episode.  I drove at least 150 miles further without any misfire.  Then I drove it a few times around town and on the bypass after having fixed the thermostat etc.  This was in dry conditions - no misfire.  It was only on a wet night that it happened - which made me think electrics.  In the bad old days, I had often had grief in damp conditions from HT leads etc.  Now we have coil packs - hence my suspicions in that area.

 

If I have to use motordiag I will try safe mode - cheers for the tip!  If the IAT sensor is the one just behind the throttle body - I have removed and cleaned it as best I could, 

 

Going back to my 'one change at a time' rule, I put the original coil pack back on but did change the spark plugs (from 3-electrode NGKs to 4-electrode Bosch). 

 

Result - no kangarooing!  Whether the cause was the cheapo coil pack or the old plugs, I don't know.  So now I'll wait and see how it goes, especially in the wet.  Luckily I have an old Clio that I am using as a stop gap, so I don't have to depend on the Felicia.  I'll bear in mind what you said about the crank sensor though.

 

Cheers folks.

Btw, I ran VCDS lite today before the coil pack and plug change.  No fault codes.

 

5 minutes ago, GaryMc said:

Whether the cause was the cheapo coil pack or the old plugs, I don't know.

Put the cheapo coilpack back on and see?

To reassure yourself regarding the HG, try removing the expansion tank cap first thing in the morning with stone cold engine.  There should not be any hiss of escaping pressure.

You're not losing any coolant?

What did the removed plugs look like, condition-wise? All similar?

Yes, I guess I could put the cheapo coil pack back on. Good idea.

 

I'll try the expansion tank cap as you suggest and check the coolant again.  Last time I checked there was plenty in the bottle.

 

The plugs looked similar - a bit dirty and wet.  But I'd only ran the car for 30secs to move it round the corner, so I guess the mixture would have been rich.  They were a bugger to take out though, so they could have been on for a while.

1 hour ago, GaryMc said:

If the IAT sensor is the one just behind the throttle body

It is.

 

1 hour ago, GaryMc said:

from 3-electrode NGKs to 4-electrode Bosch

Hold up, aren't fellys supposed to run on just single electrode spark plugs.
I think the coil pack might not like em.
For both of my cars i've used champion copper sprak plugs.
This time I'm going to try Bosch Platinum and we'll see.

Well, the IAT sensor is as clean as I can get it then ...

 

As for the plugs, that's a point I hadn't considered.  The Bosch plugs came up on the list of " suitable replacements" on the EuroCarParts website and I thought I would try them for a change.

 

I've only ever used NGK single electrode plugs in all my cars and bikes over the years and I can't say I have been disappointed.

 

It's a cheap option to go back to them in the case of problems.

 

If you don't mind, could you tell me the model number of the Champion plugs you used?

You only ever get one spark however many electrodes there are. Shouldn't make any odds.

Edited 31 October, 20196 yr by Wino
wrote should when I meant shouldn't

2 hours ago, GaryMc said:

If you don't mind, could you tell me the model number of the Champion plugs you used?

I don't quite recall but they are just the base level copper stuff when I take them out I will tell you. 

As far as the Bosch I will let you know how the car likes em. 

1 hour ago, Wino said:

You only ever get one spark however many electrodes there are. Should make any odds.

Not really you will get one stronger spark but you may get one weaker as well. 

That will affect the esr that the coil pack sees and I don't think it likes that. 

It may never harm it but who knows? 

2 hours ago, GaryMc said:

If you don't mind, could you tell me the model number of the Champion plugs you used?

Skoda recommends Champion RC89PYC.

But you can use alternative spark plugs

 

16 minutes ago, Thefeliciahacker said:

That will affect the esr that the coil pack sees and I don't think it likes that.

"esr" meaning what in your opinion?

5 minutes ago, RicardoM said:

Skoda recommends Champion RC89PYC.

But you can use alternative spark plugs

 

"esr" meaning what in your opinion?

Equivalent series resistance. 

And yes now I am making the switch from copper to nickel. 

26 minutes ago, Thefeliciahacker said:

Not really you will get one stronger spark but you may get one weaker as well.

No, only one at a time, see/listen here:

 

3 minutes ago, Wino said:

No, only one at a time, see/listen here:

 

Yes that's true they are meant to have multiple points as to maintain redundancy when one erodes the other will operate its the same principle in pcb spark gaps. 

But sometimes and under circumstances they will miss behave. 

Edited 31 October, 20196 yr by Thefeliciahacker

2 minutes ago, Thefeliciahacker said:

Equivalent series resistance. 

I thought so. Except I don't see what ESR has to do with the gaps of a spark plug.

8 hours ago, RicardoM said:

I thought so. Except I don't see what ESR has to do with the gaps of a spark plug.

Air in the combustion chamber has a certain dielectric resistance per unit length therefore the coil has to overcome that. If for any reason this drops low the thing won't have the current capability to deliver spark at such low impedance and will most likely get damaged doing so. 

That's why spark plugs have set resistance electrodes varying from 1kΩ to 5kΩ. This is meant to be a protective and stabilizing element for the coil system. 

Imagine if you replaced spark plugs with just a screw you would burn the ignition coils instantly. 

Also if you look at ngk s video you will see that you have weaker sparks going to multiple electrodes and the coils must be designed to handle this phenomenon. Who knows if the felicia ones can. 

Edited 1 November, 20196 yr by Thefeliciahacker

Dielectric resistance is not ESR. That is my point.

6 hours ago, Thefeliciahacker said:

Also if you look at ngk s video you will see that you have weaker sparks going to multiple electrodes

It is irrelevant what you (think you) see on a recorded video given the frame rate of the camera, the characteristics of the camera sensor, and many other things combined with the frequency of the sparks. Rest assured, it is only one spark at a time. As @Wino said, it is a physical impossibility. Electricity follows only the minimum resistance path at one given time.

3 hours ago, RicardoM said:

It is irrelevant what you (think you) see on a recorded video given the frame rate of the camera, the characteristics of the camera sensor, and many other things combined with the frequency of the sparks. Rest assured, it is only one spark at a time. As @Wino said, it is a physical impossibility. Electricity follows only the minimum resistance path at one given time.

Its possible but that doesn't counter the fact that you need coil pack specially designed for this type of plugs. 

7 hours ago, RicardoM said:

Dielectric resistance is not ESR. That is my point.

Yes correct but still seeing the combined impedance you will find out that dielectric resistance does play a part in the result. 

Your arguments remind me of a joke. It's called "Yes, but..."

"Yes, all my friends say I'm stubborn. But I refuse to believe them."

45 minutes ago, RicardoM said:

Your arguments remind me of a joke. It's called "Yes, but..."

"Yes, all my friends say I'm stubborn. But I refuse to believe them."

Fair enough,
it is just my opinion not trying to enforce on anyone.

On 31/10/2019 at 16:20, Wino said:

Put the cheapo coilpack back on and see?

To reassure yourself regarding the HG, try removing the expansion tank cap first thing in the morning with stone cold engine.  There should not be any hiss of escaping pressure.

You're not losing any coolant?

What did the removed plugs look like, condition-wise? All similar?

I think I've got away with it.  No hiss of escaping pressure from a cold engine and the coolant level is steady.  No misfire, no kangarooing.  In fact it's running very sweetly indeed.  I think I'll just leave it like that!  I will change the oil and filter, but that will be it for a while (and the cheapo coil pack can stay in the boot as a spare).

On 06/11/2019 at 19:22, GaryMc said:

I think I've got away with it.  No hiss of escaping pressure from a cold engine and the coolant level is steady.  No misfire, no kangarooing.  In fact it's running very sweetly indeed.  I think I'll just leave it like that!  I will change the oil and filter, but that will be it for a while (and the cheapo coil pack can stay in the boot as a spare).

Postscript:  The car did misfire since my last post.  It happened in slightly damp weather (very common near Glasgow...).

 

Anyway, I put the cheapo coil pack on and it hasn't misfired since.  That being despite some horrendous weather with lots of puddles and surface water.  No kangarooing either. Happy days!