Fine tuning idle

Guido

Old School
Joined
May 29, 2001
have a question concerning my idle.

I have a SBC 406ci, with 232/226 hyd camshaft. Speed Pro C-Com dos. 83# injectors

I was unable to get the car to idle yesterday using the demo program. I was able to use a friend's program who is using a 355, twin turbo SBC. I plugged his program in and changed the parameters to match my engine and it seemed to fire up and idle better.

I let the car sit and idle for 2 or 3 minutes and it idled just a hair around 1100 rpms. I was happy with it. But it seemed "rough". That is the only way I can describe it. It likes to float between a couple cells but not float around like a lean condition would (at least I think LOL)

after jumping around these few cells for a couple minutes, it died on me.

The TPS was at idle position so that means the speed pro is using the IAC P & D to determine how it floats around like this right?

The P was 38 and the D was 5.

If I adjust these, will it smooth this jumping around from cell to cell like it is doing and if so, then which way to I adjust these figures?

Im trying to get a better idea of how to get the car to idle better since I dont understand how to adjust the GAIN values to get this.

Thanks.
 
How did the target and actual AF ratios look? Might need to play in those couple VE cells. Might try adding some timing to try to stabilize the idle.

Others here are MUCH more knowledgable then me, so I'll let them add more info.
 
Im not sure what this guys car required but the idling AF ratio ois 13.5. That seems AWFULLY rich to me but the car is idling. Albeit FAT as hell as in our eyes are watering LOL but it idles and runs.

I started the car and let it run for 5 minutes tonight and the idle stuck really well and didnt die but it sure did make us cry a little.

Still would like a littlel bit of info about how to use the P and D gain to fine tune the idle.
 
Guido, have you read the FAST manual? it explains the P and D terms well. I never have any luck with them. Idle is kinda tricky to get it all worked out. You want me to wheel over there sometime and see if I can help? It's not that far. Mine idles and runs fine. it's really easy when you get used to it. Here's a few hints to help ya in the meantime. 13.5 at idle is fine. Helps keep the idle from wandering. Iv'e seen many idle richer. You gotta make sure the throttle follower is down around 0 at the percentage of TPS your car idles with. You gotta make sure the max tps throttle is set to 1-2 % above what it really idles at. Also, you want the IAC target to be around 30-40 when idling (look int he dashboard and adjust the TPS screw on the TB to achieve this). Adjust timing to help. I gotta get to class. I hope some of that made sense. Email me and I can help further. Like i said, when u get used to it, it's cake. Also, are u idling in closed loop? I do, but MANY say not to. If you can get away with it, i say do it. Mine idles perfect in closed loop. Welp, off to class. Good luck!
 
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