• Hi Guest we, are working on an upgrade to the forum this week, meaning the service may be unreliable at times and there will be some planned downtime at some point. Stay updated on this thread.
  • Guest, 🚨New Stock alert: Premium CUPRA valve caps now available in the store 👉 Order now from the merchandise store

Mysterious lean issue

mmisch

Active Member
Oct 22, 2022
83
18
The Netherlands
Hello,

I'm currently still checking what could be wrong with my car. (1.8t auq)

Fuel pressure is 2.8bars, fpr works (shoots up to 3 bars when vac line disconnected)
Also tested while revving, spikes to 3 bar when demanding extra fuel (as it should)
NO vacuum leaks

Vcds tells me in mvb 032 and 033 that idle fuel trims is 0.4% and partial 12.x%

If i reset trims stft spikes up instantly to ~+15%.

Weird thing is: when going WOT fuel trims go -20 almost.

Basic things like pcv/dv/hockey puck etc all have been addressed and fixed.

MAF readings spike up to 180 g/s but only at around 4k rpm and at redline its more like 140 g/s

Car is also stage 1 chipped, i don't know where. I am planning to go stage 2 but wanted to fix this issue first

Here's one of the logs i have done
Click
 

mmisch

Active Member
Oct 22, 2022
83
18
The Netherlands
Guess no one here, but my car is ready for stage 2.
Even though my maf peaked around 180 g/s, it was misreading in the normal range of rpm (2/3000rpm)
Bought a GENUINE bosch (even though it was already replaced once), and fuel trims stay close to 0% (ltft +3% and stft -5% and not +15% anymore)

My car is fixed! :)
 
  • Like
Reactions: g60stu and paradyne