Hunting idle problem on VN 5ltr with new cam

[BEGME2]

Hi all, Just did a basic engine freshen up and put a new cam in and I have a terrible hunting idle problem. At idle out of gear it is varying from 800-1100 RPM and in gear it varies from 500-1000 RPM.

The car is dual fuel and the issue is on both fuels which is odd because I have Gas Research so I would've only expected it on petrol (ECU/chip hasn't been remapped). Adding to the issue the IAC is not working which off memory I'm not sure it ever has but the problem is amplified now by the larger cam. With Gas Research the IAC is relocated from the throttle body to the strut tower so possibly the issue is in the extended wiring but I sort of doubt that as I imagine it would've been rectified during the gas conversion back in 2006. I've tried 3 different IAC's with no luck. My next thought is I know the previous owner had changed the chip in the car and I thought possibly this chip has not been programmed for idle up with the IAC, or finally I've heard the ECUs very occassionally can fail.

Any ideas or suggestions would be much appreciated guys

[cander24]

I'd be inclined to think your problem still lies with the iac valve. What size cam have you put in? In short, a larger cam is going to demand more air to run and at idle it sounds like its starving for air, hence the hunt and rev fluctuation. On the standard tune, you can often help smooth this out quite a bit by screwing in the idle stop. This opens the butterfly a little and therefore lets more air in. A functional iac will detect this and maintain the base idle speed accordingly. Maybe try approx 2 turns. Count and take note of the turns as you go so the position can be returned to standard if need be.
Id also be checking all your vacuum hoses thoroughly.
Cheers.

[BEGME2]

Thanks for the reply cander24, It's not the valve itself I woudn't think. I've changed it 3 times with no luck. It has to be in the IAC loom extension or the memcal/ecu. I've been trying to get a hold of Greenfoam through ebay to get a new memcal written but I've had no luck so far. The cam is a Crane 276. I've already adjusted the idle setting on GRA throttle body to partially compensate but I need to get to the bottom of this IAC issue and/or anything else that may be contributing to the idle issues.

[mr j-man]

is there any way to tell the factory setting/posistion of the idle stop screw??

[304runner]

Drill a small hole in your throttle body's butterfly.......

[delcowizzid]

if the iac is miles away from the engine it wont react fast enough and it also needs a tune to suit the cam sort them out it should be fine

[GRPABT1]

I would try replacing the coolant temp sensor, common cause of hunting idle and easy to do.

[304runner]

I would try replacing the coolant temp sensor, common cause of hunting idle and easy to do.

touché.....