Thread: Idle Surge / Hunting Idle - 200sx SER with Avenir swap

I could really use the help of you Nissan experts out there. I performed an Avenir SR20DET swap into my 96 200sx SE-R. I had my ECU reprogrammed by Jim Wolf Technologies to support a 300zx maf and stock Avenir injectors. The car starts up and doesn't die. The MAF seems to be working correctly (I checked the voltage and it is in spec). I don't hear any compressor surge and the car revs over 3,000 RPM. This leads me to believe that the car is healthy and distributes the appropriate levels of air and fuel through the power band. The problem I have is that the car does not idle right. It idles by revving very high and surges by bouncing up and down between 2,000 and 3,000 RPM repeatedly. It fluctuate/ surges between 2,000 and 3,000 rpm and almost seems like it is confused and/or hunting for a speed to settle at. If I add a little bit of throttle, the surging behavior stops -- but the RPM would be at 5,000 or 6,000 at that point.

My vacuum lines are connected in accordance to a number of threads that I've found throughout the web. I'm using the stock Avenir piping that goes into the throttle body which has the Avenir BOV attached to it (the stock tube and flange). I've recirculated the BOV to a pipe that I have running into the T25 turbo compressor inlet. At the end of that pipe (which goes into the compressor), I have the 300ZX maf with an adapter plate that goes to an air filter. The MAF is more than 18 inches away from the compressor inlet. I have a bung before the air filter which runs to the bung in my valve cover.

The IACV/Idle Breather connects to the cold side of my intercooler (pressurized side) via a nipple that is on the bottom of the stock Avenir BOV piping.

Despite trying several different configurations as it relates to the vacuum lines, I can't get the idle to hold steady. I've tried resetting the TPS, replugging the tps, etc. It is currently at .45V. I'm using the avenir tps. Plugging in the USDM tps makes no difference.

The only way my car runs at decent idle is if I constrict the IACV breather hose. My thought is that the IACV may not be functioning correctly and not regulating the idle.

So. I'm reaching out now for help. I really want to get this thing running stable and I'm about done pulling my hair out.

I'm prepared to pay someone to help me out (if you want to make some money and are in the Chicagoland area). Let me know your availability if you're interested and let's get this done.

Any advice you can give would be great. Thanks.

Adjust your base idle off the iacv system. There is an adjustment screw. Pinching the line to fix the issue indicates the valve is ope n too far.

Thanks zen. That makes sense but adjusting the screw doesn't change anything. The idle keeps jumping up and down. Maybe the IACV valve is not working? I just ordered a Consult cable and will try using the Conzult software to check values.

Quick would be to check if the throttle is clossed all the way or until it stops , your throttle cable gas pedal cable could be too tight, leave some slack or until it closes and adjusted, took me and my brother couple days to figure it iout know it might not be it but its an easy way to cancel it out

Yes thanks. I will have to look at that Monday because I'm not near the car right now. I believe that most likely the throttle plate is closed. The cable is not too tight... It has some slack.

When I give less air to the IACV idle breather, the idle doesn't jump around like crazy. Otherwise, if I have the full pressure going into the IACV breather from the cold side pipe, the car just surges up and down. It basically revs up and then drops heavily and then revs back up. It cycles like this indefinitely

Ok i would make sure its 100% timing set right, and bring a soapy water with a spray and strat spaying anything see if it has any leaks , intake manifold, throttle, ic piping, bov, all vacummz that would be an easy step to keep canceling things out

Ok guys. I had an opportunity to work on the car again today. I went ahead and serviced the USDM IACV (cleaned it up real good and made sure the mechanism was working). I affixed it to the engine, but it made no difference. I also had a spare N62 MAF that my friend lent to me for testing, but that made no difference either.

I really don't get what the problem is. I believe there is too much air going into the engine because if I plug the intake up a bit, it doesn't surge the way it is doing now. I've posted a video below of my issue. Any thoughts?

Anyone? Advice?

Ditch the jwt ecu.. seriously

Do you think that the JWT ECU could be the problem? I know that many people on this forum have recommended and stood by JWT as the "holy grail" of solutions. It certainly was not a cheap purchase.