False Lean Idle Condition?

[tonydee64]

Hey guys, I think I have an easy one for you. I have yet to get my car on the road and I am new to this fast ECU, but I've read up on it as much as possible. Anyway, from the very beginning my car pumps out visible black smoke at idle (enough to make your eyes water in the garage). I finally was able to run a data log tonight and sure enough my actual A/F ratio stayed real close to the targeted A/F ratio, around 14.1-14.5 (the O2 sensor was making the proper adjustments). This has always perflexed me and I made sure that I don't have any AE fuel kicking in (the Aft corr% is at zero). I also changed my plugs as they were black (obviously rich).

I have my closed loop set for 500 rpm so it will work during idle.

Here is what I'm thinking... I read in the FAST facts that if you have a large exhaust and/or a long duration cam you may be getting a false lean condition at idle due to a lack of air movement over the O2 sensor. I have dual 3" exhaust and a long duration blower cam.

I'm thinking that I need to take the ECU out of closed loop during idle and simply take fuel out manually from the base fuel table at idle. I guess my question is: How do I know that my A/F ratio is correct at idle? By simply looking at the plugs...

Would any of you be willing to send me a gct. file of your setup? I have made guesses for mine based upon what I have read, but I have no idea if I am even in the ballpark... My e-mail is Tonydee64@sbcglobal.net Thanks guys...!!!

 

[Ricky Trussell]

Set 02 correction at 1000 rpm. Then take the four cells in the ve table around the idle marker and bump them down slowly until the engine starts hunting then bump it back up until it settles down. Do this slowly. You can watch your A/F ratio while you do this.

This is assuming you have no other issues. I would worry about flooded plugs and a A/F 14.0 reading.

I have a 242 dur. at .050 cam but I still run 14.0 a/f ratio with 02 correction at 780 rpm.

 

[tonydee64]

Thanks for the advice Ricky.

Here is how I solved it... I did set my open loop to kick in at 1100rpm. I was then able to get car to idle in a warmed up state without any after start enrichment. The idle speed was lower than my target idle the engine started to load up again and run rich unless I manually took out so much fuel that the car would almost die. That told me that the TPS was set too low (kind of like a choke on a carb.) I opened the TPS until the motor starting picking up RPM enough to reach my target idle... and then put another turn on it after that to let the IAC do its thing. Then, I was able to play with the VE base fuel table to achieve a smoke free idle and the motor seems more lively and not so lazy and sluggish. Of course I also made sure that my target timing macthed up with the actual timing light reading. I'm sneaking up on it slowly but surely... Now, onto tuning for boost and acceration. I hope I don't blow this thing up.

 

[Ricky Trussell]

Glad you got it running good.

I don't understand what you are saying refering to the tps. You have a screw adjust on a throttle position sensor?? Or are you refering to the throttle blade adjust screw?

Did you try closed loop again now that it is tuned better??

 

[tonydee64]

Originally posted by Ricky Trussell
Glad you got it running good.

I don't understand what you are saying refering to the tps. You have a screw adjust on a throttle position sensor?? Or are you refering to the throttle blade adjust screw?

Did you try closed loop again now that it is tuned better??

Sorry, I meant the adjustment screw on the throttle blades.

I did not try it again in closed loop. As I mentioned I am, slowly closing in on my tune. The only other issue I have before I can safely drive the car is a slight stumbling off idle. I think I will try increasing the AE vs. Throttle position % to get more of an accelerator pump effect, and if that doesn't work I'll add slightly more fuel to the VE table as appropriate. I think my timing is pretty close and none of my tables have any steep transitions from one cell to another. As a computer programmer 15 years ago, learning about this is way more fun than taking it to a tuner and dropping it off.. as long as I don't blow it up. I think I'll be fine as long as I go slow and watch for trends in tmy VE table (so I don't go too lean for lack of fuel inputted values.. even with positive correction) and keep the A/F ratios and timing reasonable. Is there any way to slow down the data log playback? It goes by so fast I can't make adjustments where needed..Thanks Again!

 

[Ricky Trussell]

You can open the log and then use the arrow buttons to move the log. You do not have to autoplay.

 

[tonydee64]

Originally posted by Ricky Trussell
You can open the log and then use the arrow buttons to move the log. You do not have to autoplay.

Ahhhh. appreciate it.. thanks again!