I recently installed a Defi VSD X on my IX and my mechanic had to plug something out from the ECU to attach the wires, after that my car keeps stalling and they had to adjust my idling. The problem started from here. Every time I release the throttle on boost (no matter how much) and release the throttle, my rpm does not dip immediately but rises by 500-1000rpm before dropping down. After that I took out one of the battery cables for like 10 minutes and put it back on hoping to reset the ECU but the problem is still there after driving for like 4 days.

Any clue what this might be? The idle valve? or does it sound more like a tuning issue?

 

Go back and find out which wires your mechanic modified (or those around it he may have damaged) and check to make sure all the connections in the wiring are well done and the plugs are seated.

 

All the wires are seated properly. The explanation they gave me was that my ECU is reflashed and by unplugging it and replugging it again, they might have caused s soft reset and the ECU has to relearn the car all over again. Does that makes any sense?

 

not really

 

I might not have made myself clear. What I meant was that my ECU was reflashed by ECUTECH and by unplugging it and replugging it again for the installation of the VSD, they might have caused s soft reset and the ECU has to relearn the car all over again.

 

Does it make any sense now?

 

In a way it does... I know at work (I work at BMW) whenver you reprogram the digital motor electronics, known as pcm to most people, on some of the vehicles you need to let the car sit with the key on for 10 seconds or else the car will run like crap. It sounds weird to me that after you let off the throttle the rpm raises... If our cars were drive-by-wire I could understand more but changing ecu stuff? Did they mess with any of the throttle cables? And, when you let off the gas do you hear your BOV right away or no?

 

take it back to the mechanic. Iam not sure if the EVO ecu uses fuzzy logic or not. If it does, then yes it has to relearn its maps again but if thats the case then that only takes a couple of seconds not days.

 

Yes an EVO and most other cars will have to relearn idle when power is disconnected to the ECU (Disconecting Battery, unpluging ECU). But that doesnt effect your RPMs shooting up between shifts.

Behind your valve cover your throttle cable is attached to a slide bracket. was this taken off for any reason. If so it may be adjusted to tightly causing the butterfly to stay open

 

Usually drive cycles which can add up to days depending on driving habits

 

It is documented in this forum that some DVs will cause this rpm raise. Also if the speed adjusting screw(sas) is adjusted it will cause this too. Sometimes it will "trim" out, sometimes not.
The best way to do an sas adjustment is with MUT 30 actuator test which stops the idle air valve at its basic position. Evoscan 2.5 has this feature now, called SAS actuator test that works like a charm.