AGU overfueling ,weird idle , feels like not getting full boost

[JogiahMk4]

My recently rebuilt agu has been acting up. When the car is hot and is idling ,I see white smoke coming from the exhaust, its definitely overfueling as there is a small backfire and it smells strongly of fuel .I pulled the spark plugs recently and they seemed to have a slight white build up on it . I did clean the maf ,it seems to be in good condition. It doesn't seem to be getting full boost but I'm not sure about that. Also the idle seems to fluctuate constantly by a couple hundred rpm.


The turbo is reconditioned ,rings and bearings are all new and the car is getting full compression. I did try running a vcds scan but it did not work as the ecu wasn't communicating with the scan tool .

I also tried pulling the connector to the maf off but the car dies immediately after.

[Jetta2]

If it was overfueling, the plugs would have black soot on them.

A white build up is an indication of running way too lean.

Check here: https://www.championautoparts.com/Parts ... plugs.html

White smoke from the exhaust usually indicates coolant is being burnt in the combustion chamber due to a head gasket not doing it's job.
Or on the AGU, a turbo seal could be leaking, or the brake booster/master cylinder could be failing.
The brake booster works on vacuum and brake fluid burns white out the exhast if that is the case.

Who rebuilt the motor and turbo?

[JogiahMk4]

My cousin and uncle rebuilt the motor and I was there throughout the process .they've been building engines for years , everything was done correctly, no shortcuts were taken . The turbo was done by a shop yjat came highly recommended. The car definitely is overfueling though, the fuel economy is gone to dirt and fuel is burning in the exhaust as you can hear it . It's a stock exhaust too.



The smoke or fumes doesn't have a sweet coolant smell either ,it's a strong petrol smell. The problem seems to be intermittent as well . Some days no smoke some days it'll smoke .


Any other possibilities?

[PapaJo]

Did you scan for error codes, verified fuel pressure is correct, checked for boost/vacuum leaks??

[JogiahMk4]

Did you scan for error codes, verified fuel pressure is correct, checked for boost/vacuum leaks??

The vcds tool won't communicate with the ecu unfortunately. I will try removing my headunit and check fuses when I have access to the tool again . Thinking of buying a cheap one for myself in the near future as well .


Will be trying to do a smoke test soon as well just don't have the tools for that

[JogiahMk4]

Did you scan for error codes, verified fuel pressure is correct, checked for boost/vacuum leaks??

I was also thinking it has something to do with the PCV system did anyone else have these kinds of problems ?