Idle issues and solution.
Triumph Stag v8, 3 litre with basic fuel-only fitech.
My cars idle has been very unstable, to the point where I eventually just unplugged the iac when it happened to be warm and ticking over at about 1000 rpm. Cold starting is ok, just use a bit of throttle.
It is a bit irritating though, as the conversion works pretty much perfectly otherwise.
It is not ideal though, so I was pleased to find a YouTube video showing how to make a manual adjuster for the IAC. Not expensive, but a bit fiddly, lots of wires & soldering.
I got all the bits from eBay, and I can confirm the circuit works as described, and drives a stepper motor in either direction with a push on a switch.
I now need to fit it to the car for final proof. Just waiting for a suitable connector pigtail for the IAC, it doesn’t seem to be a common size.
I don’t seem to be able to post a link, so for those interested, the YouTuber is called ‘Comeinhandynow’ and the title is: How to make an engine idle speed control circuit.
He has lots of other diy stuff too.
Good luck
Huw
All connected up now and the car is much better to drive, with a stable, adjustable idle speed. Unexpectedly, on shutdown, the idle valve opens ready for a cold start as the fitech stays energised for a few seconds, so the idle has to be reset each start. Still better than the unpredictable flaring and stalling though.
Hope this is helpful to someone.
Stage2.
The manual idle control was a bit inconvenient, although it did work.
I have tried a different approach by putting a restrictor in the iac valve intake port, reducing the diameter from 10mm to 5.5mm. This limits the airflow enough to prevent a very high idle, and as the iac is operating in a lower pressure, it alters the response to iac movement. So far it seems to work well on this relatively small (by fitech/USA standards) engine. If it won’t open enough to idle from cold in really low temperatures, I can drill it out a bit, perhaps to 6mm.
So far, the ecu seems to be coping with it ok.
Thanks Velosolex50,
Useful info, especially the idea of a restriction in the IAC circuit to dampen the responce.
I'm running the exact same basic fuel-only 400hp fitech on a 3500cc (215cu) Rover V8 in an old Landrover 90.
My conversion has worked pretty well too with very little tweaking required.
I haven't had any problems with idle stability ( it's happy and lands pretty well back to a 750 rpm target) , but good to know there are solutions to try if I do.
Links for the youtube video mentioned in post #1
The channel: Comeinhandynow
The video: How to Make an ENGINE IDLE SPEED CONTROL Circuit
Some settings that that may be useful to someone.
I am running a little 3500cc 215cu Rover V8 with the mildest cam possible and may have 125 hp.
I am still running the early 3003 T195o software - so there isn't a lot that I can adjust, but have activated the main menu > display setup > PRO calibration > show to access all the available parameters.
Warm idle speed = 750 (default=800)
Decel IAC decay = -50 (default=0, this made it drop back to idle more like a carby)
Crank IAC = 50 (default=100, tamed the flaring nonsense on startup)
Accel Pump 20,65,170F = 20 for each (default=0 for each, got rid of lean stumbling and hesitations when getting back on the throttle)
Fast Accel 20,65,170F = 20 for each (default=0 for each, same as above, though I don't think this had nearly the effect as adjusting Accel Pump)
Dfco Enable Temp=300 (default=68, turns decel cut off, just confuses things I reckon)
Warmup 20,65F = -60 for each (default=0, seems to have reduced somewhat the overly rich drama when starting from cold)
Interesting. I would have never thought of adding an external circuit to control the IAC.
I had a nagging issue with hanging idle that bothered my for a long time until I adjusted the rear butterflies. The rear butterflies would stay open due to the built-in play of the linkage. Look in this post at the instructions from FiTech on how to adjust both the front and rear butterflies. This fixed the issue for me. Now what I have is a fluctuating idle issue that I have had for years where the idle speed is in between 800 and 1000.