RomRaider

Hello all, I am having an odd issue regarding the tuning of my m52tub25 with a sc14 supercharger (no kit, grassroots style and custom plumbing).

The engine runs great with boost, until I am off throttle. When off throttle the dme goes into limp mode, throwing a p1500 code for the icv "stuck open". With the supercharger disconnected I do not encounter this issue, ever. However, with the supercharger connected it will happen in rpms as low as 2500 if I let it decelerate on its own.

Partial throttle=okay
Full throttle=okay
No throttle=P1500 (limp mode causing code)

I think it seems to be an issue with excess air in the maf from the blower. I do have a blow-off valve pre maf (vw 1.8t type bov), but it could possibly be undersized (25mm diameter I think). This was happening on a pulley that only ran 1.5 psi to the manifold (now on 5 psi). If the car gets put into neutral off of high rpm I do not get a code.

If anyone has input on the maps I need to adjust I will be over the moon. I will be trying some map adjustments I found off of ms4x.net. They're for an ms43, but I will see if there are comparable maps on the ms42.

Thank you.