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Discussion Starter · #1 ·

I've been fighting general driveability issues on my 16v Swapped 1991 8v Gti. I have been chasing this problem for months and am looking for some help!

Vehicle Specs;

1991 Golf Gti 8v - (Received the vehicle for free, needed extensive work)

9a 16v swap
  • BBM fuel rail
  • Digifast ECU Chip
  • Techtonic Tuning Cams
  • Ported intake manifold
  • Cold start injector delete
  • External Oil Cooler

The issue;

Started while the car still had the 8v. As the vehicle was being painted, the hood was left off and the engine was covered in snow. After drying it off, and getting it started the car ran incredibly rich and idled very poorly. Would fowl the plugs after running for a short time and warming up had excessive blue smoke and ran like a rotary at idle. I couldn't figure out the issue and found a complete 9a 16v already set up for Digi II. After doing the swap once the car warms up it would continue to run very poorly with hesitations under throttle and terrible idle, but no smoke. The motor was running perfectly in the vehicle it was just pulled from. After sorting through all the usual Digi II culprits (ECU grounds, 02 sensor, ect..) I found a fix that allowed the vehicle to be driven. This being the infamous blue Water temp sensor. I swapped the black water temp sensor (For the gauge) from the old 8v into the port on the 16v where the blue plug sits, for a test. The car idled much better but still has a hesitation under quick throttle response (ex. downshift) and I worry it's running quite lean. I purchased a brand new blue water temp sensor from VW to replace the black placeholder sensor. Much to my surprise the car would barely idle or rev up at all with the brand new sensor. I also attempted to swap in a 6 cyl BMW aftermarket cold air intake / maf that had run on the previous vehicle with this swap. This also caused the car to run incredibly poorly, so I swapped in the stock intake box / maf sensor which allowed the car to run better. if anyone has any insight into what the issue could be it would be greatly appreciated! Quick summary below of the issue with less info...

  • Slightly poor idle (hard to tell with cams)
  • Hesitation/stutter under heavy/sharp throttle

Thanks for reading!
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