Trying to swap AXX engine with BWA

[joeb]

Hey guys,

I just made an account on here today as recently I just bought a 2005 gti thats had its original AXX engine swapped out with a BWA one. The guy I got it off had the low oil pressure stop engine warning with the AXX, so he got it swapped out for a BWA, yet the same warning light comes up. The engine still starts but the fan is on, and it had difficulty driving onto the car transporter.

I've tried checking for fault codes with a ELM327 scanner, and the only code that came up was one about the MAF (as it wasn't plugged in).

Apparently the engines are interchangeable, although the BWA uses more boost due to the difference in the compression ratios? How would the AXX ecu accommodate for this? Thats presuming the AXX ecu is still in there, I'm not entirely sure how to check that.

Any knowledge about the swapping of these two engines, ecu compatibility, etc would be very appreciated!! Cheers

[Ricky123]

There completely interchangeable... never heard of BWA running more boost but sure someone else can shed more light on that.

I’ve personally done a AXX to BWA swap with no issues at all and I didn’t see any differences. It may be worth checking what sump is fitted to it though as seat Leon’s and maybe others that came fitted with BWA engines don’t have a sensor in the sump like the mk5 gti’s do so if the donor engine came from a car that didn’t and they haven’t swapped the sump over then you will see warnings relating to oil.

[mjmallia]

If doing an engine swap, it will be worth pulling the sump off anyway to clean/check/replaced etc the oil pick up for peace of mind.

[probedb]

Mine was a direct swap.

[joeb]

If doing an engine swap, it will be worth pulling the sump off anyway to clean/check/replaced etc the oil pick up for peace of mind.

Yeah I've dropped the sump and cleaned out the oil pick up, sadly it wasn't as bad as I was hoping for. There was some sludge in the sump and a small amount of black deposits in the pick up pipe.

I then changed the oil filter and oil. The old oil was rather nasty, and the oil I put in was 5w40.

I started up the car and it ran at idle for about 5 minutes with no oil pressure warnings. Then, after about 6 revs at approx 2.5k rpm the oil pressure warning came back on. I then turned the car off and turned it back on, presuming the alarm would come on straight away. But no, only after it running for a minute and giving it a few revs it came back.

I'm now planning on disconnecting the oil pressure sensor and seeing what happens. As I'm thinking possibly when the engine was swapped over it was plugged in wrong. So by unplugging the sensor maybe the oil pressure warning will come on straight away? Or maybe even a completely different warning light will come on if its plugged into the wrong spot?
Any thoughts on this?
Cheers

[Ricky123]

i’d change out the oil pressure switch for a new genuine one and see if it’s still the same then go from there, while doing that just inspect the plug/connectors and loom for any damage.

If your still seeing warnings with a new sensor then it could be a genuine internal issue.

If you take the oil cap off Does the top end of the engine look like it’s getting plenty of oil after it’s been running? How does the engine sound? Any unusual noises?

[joeb]

i’d change out the oil pressure switch for a new genuine one and see if it’s still the same then go from there, while doing that just inspect the plug/connectors and loom for any damage.

If your still seeing warnings with a new sensor then it could be a genuine internal issue.

If you take the oil cap off Does the top end of the engine look like it’s getting plenty of oil after it’s been running? How does the engine sound? Any unusual noises?

I sorted the low oil pressure warning today.
It turns out the oil pressure switch wasn't plugged into the connector. It sounds dumb but I didn't think to check that at first as the low oil pressure warning wasn't instantly coming up. It took about a minute for it to come up, even though the sensor wasn't plugged in.
I tried plugging it back in but it wouldn't go so I took the sensor out and it turns out the sensor was 2 pin and the plug is one (must be a change to BWA from AXX?). So I got a sensor from a spare AXX engine I have and put that in and no more low oil pressure woo hoo!!!

Yet, there is still issues with the fan coming on just after starting it. It's idling rough which may be related to the fan, and the yellow power steering light and traction control light are also on. Has anyone had any experiences with these?

[Ricky123]

Is the AC on or if it has an ECON button then is that off? Just worth a check because the fan will come on for the AC.

If not then check the fan wiring if the front end was removed when installing the engine Also check the fan relay as that could be faulty.

As for the steering and TC lights they normally come on if the battery has been disconnected/ gone flat and it hasn’t been driven since. If that’s the case then they will go off after a short drive.

[joeb]

Is the AC on or if it has an ECON button then is that off? Just worth a check because the fan will come on for the AC.

If not then check the fan wiring if the front end was removed when installing the engine Also check the fan relay as that could be faulty.

As for the steering and TC lights they normally come on if the battery has been disconnected/ gone flat and it hasn’t been driven since. If that’s the case then they will go off after a short drive.

It was a broken wire which caused the issue. The fault is gone now.

Only fault left is:
Intake manifold runner control open stop outside valid range

Not entirely sure was this means? Tumble flaps possibly? The car seems to drive alright though.
Cheers