Fabia 1.4 16v BBZ Misfire Cylinder 4

[JDJnr]

Hi all,

Last weekend I purchased the good lady a 55 plate Fabia 1.4 16v 44,000 miles.

Its seems the seller forgot to mention that once the car warms up, the engine light flashes and the car starts to mis-fire.

Not only did he forget to mention this he also didnt mention that this has been going on for sometime, as I found out from researching this forum for an easy fix and I came across his posts.

Getting back to the fault, I have plugged in the diagnostic machine and found 1 fault (16688

Misfire detected cylinder 4).

I have tried the following and failed to move the fault;

Swopped spark plugs 1 to 4

Swopped coil packs 1 to 4

Swopped injectors 1 to 4

Swopped injector wiring 3 to 4

Is there anything else easy I can try?

I will be having a compression carried out in a couple of days, but I'm hoping for an easier fix (not holding my breath).

Thanks in advance

[JDJnr]

Carried out a compression test this evening and found cylinder four was at 11bar and the others were 15bar approx.

Cylinder head will be coming off tomorrow, to assess whats causing the lower reading :(

[Taylor93]

I believe VAG attempted to fix the problems with the AUB block, i.e. carbon build up eating the piston Rings. when they released the BBY/BBZ block. I dont know tho if they actually fix the issue.

I dont want to be stereotypical, but is there a chance the "good lady owner" used 95 Octane fuel, that the engine didnt like at all, and decided to eat its rings? instead of using the 98 octane.

Also, are you running it on 95 or 98 octane? a higher octane may help?

[Tech1e]

I wouldn't go taking the head off just yet.

Check the EGR, this is fed off cylinder 4. If its stuck open, would drop compression.

[JDJnr]

"Check the EGR, this is fed off cylinder 4. If its stuck open, would drop compression."

Thanks for the info, I will make sure the EGR valve is checked prior to removing the cylinder head.

Would this explain why it only misses once its warmed up?

As for the fuel situation, the wife has'nt really had chance to drive it yet and I have no idea what the previous owner has been using.

But after reading through several different posts, we will be using 98 fuel going forward.

[JDJnr]

Have'nt managed to get the EGR off yet, what with all this rain.

Can anybody advise/explain why the car stops misfiring for a few minutes when the fault/fault light is erased?

[JDJnr]

Thought I would update this for anybody requiring this information in the future.

The best way I found to eliminate the EGR valve was to block it off, I did this by removing and re-fitting it backwards, in turn blocking off the port in the cylinder head.

I then carried out another compression test and found that it had improved slightly, but was still down by approx 3 bar.

Next job was to remove the cylinder head and take it for testing (Cranmore Engineering, Birmingham), after leaving it for a few hours it was ready to collect.

It required new exhaust valves on cylinder four and the head skimming (£70).

Cylinder head has now been re-fitted along with a new gasket set, cambelt kit, water pump, throttle body cleaned, fault lights re-set and a full service undertaken, we are back to running as it should do, with no thanks to the ****** who sold it to me.

[Avalon]

If he's genuinely misrepresented the car and the posts show he was aware of the issue then the Sale of Goods Act would be worth a read followed by moneyclaim.gov.uk. No excuse for deliberately misleading people about the condition of the car if you are aware of it.