VW scirocco 1.4 TSI ONLY misfires between 2000-3000rpm

[colossus]

Hello

I am new to the forums. I will do my best to be active on the forums. Now let's dig in.
We have done a rebuild on a CAVA engine 1.4 TSI VW scirocco due to broken piston (common problem). We put on new KS pistons +0.5mm, new upgraded timing chain kit 03C198229C (original VW), new kit for oil pump (chain tensioner), new shaft seal for crankshaft (corteco), water pump, belts, cleaned, repaired and tested injectors, valves grinded on cylinder head perfectly, new gasket kit for everything, new filters (including fuel filter), new spark plugs ect.

So the problem here is that the car cranks perfectly, works and sound very smooth on idle. Revving the engine up to 4000rpm runs perfectly and the only issue that in misfiring between 2000-3000 rpm if you keep it there steady for a few seconds. The check engine starts to flush and through live data you can see A LOT of misfires on 2nd and 3rd cylinder. If you stay there for another 2 seconds EPC comes on and disables the cylinder (stops the injectors on 2nd and 3rd cylinder).

We took out the injectors again, send them to the technician for a recheck. In fact he cleaned them again and tested them. Nothing wrong. We swap them places from 2nd and 3rd cylinder to 1st and 4th cylinder. Put everything back on and the problem still insists.

We will do more check by Tuesday once we are open again. But i suspect that the car will need a software update in order to match all the new parts and upgrades it has right now on the engine. I will gladly hear your opinions below!

Thanks
Chris

 

[Crasher]

It isn’t clear if the misfire moved with the injector swap. Is it on the same cylinder as the failed piston? Did you rebuild the head?

 

[colossus]

It isn’t clear if the misfire moved with the injector swap. Is it on the same cylinder as the failed piston? Did you rebuild the head?

Sorry i haven't clarify it above. By moving the injectors problem still insists for the 2nd and 3rd cylinder.
For the cylinder head we did valve grinding and changed all the valve seals with new ones

 

[Dr Sheldon]

Dynamic Compression test is a good place to start

 

[Dr Sheldon]

We have done a rebuild on a CAVA engine 1.4 TSI VW scirocco due to broken piston (common problem)

Common ?? Is it ?

 

[colossus]

Common ?? Is it ?

Yes it is a common problem. Either piston rings or piston. As for the compression test we will do it once we are open, thanks.

 

[Dr Sheldon]

But i suspect that the car will need a software update in order to match all the new parts and upgrades it has right now on the engine.

You barking up the wrong tree there !!

I very much doubt that a software variation could fix a misfire on cylinders 2 & 3 where oversized pistons have been fitted, and then I would bet that VW would not be writing that !! Why would they ??

With you having swapped all the bits about

Nothing wrong. We swap them places from 2nd and 3rd cylinder to 1st and 4th cylinder. Put everything back on and the problem still insists.

A good plan now would be to have a Scope on

1. All Coils looking at Voltage and Secondary Current
2. Upstream o2
3. Crank Sensor
4, Pressure Transducer in Dipstick

 

[Dr Sheldon]

We took out the injectors again, send them to the technician for a recheck. In fact he cleaned them again and tested them. Nothing wrong.

Those injectors cannot be tested conclusively by any human being once removed from their natural habitat in the car !! The environment they live in would be too difficult to exactly replicate on a bench - The Bench would have to be an Engine !!

 

[Dr Sheldon]

works and sound very smooth on idle. Revving the engine up to 4000rpm runs perfectly and the only issue that in misfiring between 2000-3000 rpm if you keep it there steady for a few seconds. The check engine starts to flush and through live data you can see A LOT of misfires on 2nd and 3rd cylinder

Lets think about Valve Springs - dynamic components built from a material that has the DNA where its characteristics can change with heat, oscillation, frequency and more ?!!

Hence I suggested the Dynamic Compression Test - Be sure to remove the Schrader valve from the Compression tester !!

 

[Crasher]

It is a nasty problem with the CAVD/E, improved from 2012 but it still happens. It is caused by detonation from the use on 95RON fuel which they really don’t like.

 

[Uwe]

It is caused by detonation from the use on 95RON fuel which they really don’t like.

Do these engines not have knock sensors?

-Uwe-

 

[Crasher]

Yes and they work but only after detecting knock so after thousands of cycles, the ring land fails.

 

[colossus]

Do these engines not have knock sensors?

-Uwe-

Yes they have knock sensor and it’s on the engine block behind the supercharger. We haven’t even touched it! This engine has only 70000khm. And the owner was only using 98 unleaded. But those engines still have those huge problems. I appreciate everyone that is trying to help. I will keep everyone updated