I've had a rebuilt engine fitted into my 2008 Octavia 2 vRS, it's a 170hp BMN engine.

During the break-in period I drove it very lightly (never exceeded 2000 RPM) and it drove great, but problems begun after starting to push it a bit further. When driving in any gear other than 1st and 2nd and accelerating past 2-2,5k RPM the car stutters (sort of rocks back and forth) and then after a few seconds or re-applying the throttle accelerates further, but struggles to move past 3000 RPM (I have not managed to get it past 3,1k RPM).

First though was to check the fuel filter - so I did that and checked and replaced as a precaution, also added some injector cleaner additive, but that seemed to do noting and the issue remained the same. No warning lights on dashboard, no smoke or anything that could be obviously noticed.

 

Scanned fro faults as well and there was nothing logged, so any help would be greatly appreciated!

Never exceeded 2000 RPM... it might be all coked up!

 

Drive it like a hire car.

Just following the shop's recommendation, not a fan of that either lol

You're saying I should take it to a motorway and give it full gas for some miles even if it's stuttering like hell and see if that fixes the issue?

Not exactly as there could be actual problems that haven't been diagnosed.

 

What distance have you covered at <2K RPM?

Makes sense.
 

1 minute ago, MicMac said:

What distance have you covered at <2K RPM?

 

Around 200 miles.

Update: Not fixed yet but we have a first diagnosis.

 

I’ve visited a bloke that has access to VCDS and some spare time and we went for a longer drive to see live data and what the sensors were saying. Checked all the values that could be relevant - including EGR readings and some other less obvious things. 

 

While everything was correct, there we’re really no values standing out too much, the only thing that was out of place (which we noticed on the graph) was the amount of fuel flowing to the engine/injectors. (Sorry for a poor description I’m not a technician and only know the basics).

 

This means that the first suspect is the in-tank fuel pump.

 

I will be replacing it this week and let you know the outcome 🙂

 

I doubt that is your issue, the pump only operates at ignition on for a few seconds to prime the filter assembly.

 

Perhaps the tandem pump is worn and not supplying enough pressure to the injectors.

 

Have you checked the vacuum system and correct operation of the turbo?

Worth a check anyway I suppose  
 

4 hours ago, MicMac said:

Perhaps the tandem pump is worn and not supplying enough pressure to the injectors.

 

That's definitely a valid point! Is there any way to test this? Would it be visible on disassembly?

 

4 hours ago, MicMac said:

Have you checked the vacuum system and correct operation of the turbo?

 

Everything controlled with vacuum seems to operate correctly, the turbo was also providing the correct pressure according to VCDS.

I wouldn't strip the pump prematurely, I don't believe there is a fuel pressure sensor and so it would need a garage to check the pressure/flow.

Definitely didn’t mean to disassemble the pump itself, quite a complicated bit of tech there, what I meant is would I see anything when taking it of the engine - but from what I’ve researched that’s not the case. 

 

That being said, they don’t cost all that much, so I will just replace it along with the in-tank pump.

 

Thanks for the help and I will keep posted.

You are wasting money, have a garage check the fuel output.

 

The lifter pump has nothing to do with the issue.