AUM 1.8t either running poorly or not starting at all!

[Lingo89]

Hey guys, having massive issues with my A3 1.8t (AUM). This is following an engine conversion from the 1.6 (AVU).


Basically, it will have days where I will turn it over and it will start and idle fine but then, when it's running it's very jittery, it's as if the turbo boost is cutting in and out and it can't decide whether to go or stall, it will drive very slowly even at full revs. Alternatively, some days it will turn over all day but won't start.


The fault codes I'm constantly getting on VCDS after clearing everything and trying again are as follows, I've already changed the camshaft sensor and MAP sensor so I can't see those being the problem:


4 Faults Found


16621 - Manifold Pressure / Boost Sensor (G31): Signal too Low
P0237 - 35-00 - -
16490 - Manifold / Barometric Pressure Sensor (G71) / (F96): Implausible Signal
P0106 - 35-00 - -
16727 - Camshaft Position Sensor (G40): Signal too High
P0343 - 35-00 - -
18041 - Accelerator Position Sensor 2 (G185): Signal too Low
P1633 - 35-00 - -



Any help would be much appreciated, as I am at the edge of my wits over here.

 

[<tuffty/>]

Wiring I would imagine... check all the earths... for a lot of sensors to give fault codes like that there will no doubt be an underlying problem... its rare for any of these sensors to go wrong but when they do play up its normally wiring related and considering yours is a conversion then thats only going to add to the issues you have here...

If you have spliced the loom in or used a loom from a damaged car then who knows what issues you are likely to have....

Good luck, wiring faults can be a ****** to track down....

<tuffty/>

 

[Lingo89]

Wiring I would imagine... check all the earths... for a lot of sensors to give fault codes like that there will no doubt be an underlying problem... its rare for any of these sensors to go wrong but when they do play up its normally wiring related and considering yours is a conversion then thats only going to add to the issues you have here...

If you have spliced the loom in or used a loom from a damaged car then who knows what issues you are likely to have....

Good luck, wiring faults can be a ****** to track down....

<tuffty/>

Cheers. We were thinking wiring fault too. We've not spliced the loom, we're using the engine loom up to the ECU as well as the engine loom from the ECU to the interior from the donor AUM engine. We are however using the original AVU 1.6 interior loom but I can't see that being problematic.

How many earth's are there in total guys? that's certainly what we'll check next.

 

[<tuffty/>]

Most of the relevant earths are under the battery tray... there are two posts from memory....

<tuffty/>

 

[Broken Byzan]

My guess would be from doing similar stuff, you have missed a power feed somewhere. On all the occasions I have done an OE wiring upgrade/ swap, there was at least one extra power wire needed . The 1.8 t loom from memory will expect a feed to go into the car thru a fuse and back to one of the engine power feeds

 

[Lingo89]

Most of the relevant earths are under the battery tray... there are two posts from memory....

<tuffty/>

Tuffty we tried cleaning those two up already, oddly enough it did seem to make starting a bit better but turned out not to be the root of the problem.

My guess would be from doing similar stuff, you have missed a power feed somewhere. On all the occasions I have done an OE wiring upgrade/ swap, there was at least one extra power wire needed . The 1.8 t loom from memory will expect a feed to go into the car thru a fuse and back to one of the engine power feeds

Interesting Byzan, this sounds promising. Would you kindly elaborate on what you mean here?