Strange idle o2 Issues

[gmorris]

I'm hoping someone can point me in the right direction of a strange idle o2 issue I'm having. I have been fine tuning this car all spring and have most areas dialed in but have been getting some idle weirdness where at first start and any time you blip the throttle even slightly the o2's quit switching for almost a minute. The will stick lean and it will go to massive positive trims without any real affect then after a few seconds the go rich and sit for a while before starting to switch properly. Is there an idle o2 delay setting somewhere I'm missing? I was under the understanding that the o2 delay was just for startup purposes?

If I go open loop the AFR remains +/-3% so I believe my ve and maf are pretty close. I have relocated and dialed in the o2's o where they are good everywhere but this...although I have messed with my idle so much lately it's hard to remember what I'e tried. I've moved my idle timing around and it seems the best compromise at 9? although 12 or 15 works as well but I get more idle speed error.

Engine is a 418 LS3 from texas speed in a '69 chevelle
PRC heads, 235/239 cam
E38 ECU with stock LS3 intake and injectors.
Long tube headers, no cats, full duals

Idle 1 is a hot start and idle 2 has a very small throttle blip in the middle.

On another note, dose my timing table seem unreasonably low for an 11.25:1 ls3 on 94 octane pump? Any more and I get a lot of knock retard at peak torque.

Thanks!

[SMEC]

IMO I would have more timing at idle.

download a 09 corvette tune from the Tune Repository and go to

Fuel>power enrichment>pe throttle/pedal hot change those numbers to the tune you download to your tune

also go to EQ Ratio and change those to what you want the afr to be at WOT (14.7/your target afr= those new numbers in EQ Ratio).

also go to Enrichment Ramp In change that to 1.300.

My thinking is since you're commanding PE via pedal position at 9 to 12% and you touch the throttle in the 2nd log (30% in the scan) the car is going into PE and the enrichment ramp in at 2.000 means its dumping a shit ton of fuel. Your wideband show it going rich too.


your lean issue- go to your maf table:
2550hz to 2700hz in your maf table isnt right also this might be why you go lean. at 2550hz your at 93 then 2700hz its at 57 then at 2850hz its goes to 130. highlight 2550hz to 2850hz and smooth it till it looks awesome, same with the whole maf table.

Hope this helps, other welcome to tell me if I'm wrong

[JBZ]

OP first off I don't see your O2s being logged in the file you provided so its hard to get an idea of whats going on.

if they are not switching fast enough and its an a fuel trim swinging problem you may need to adjust your integrator delay, proportional base and airflow mode in the open & closed loop fueling. look for the thread I started O2 sensor tuning with headers. that is all about these setting ans getting the desired results out of my O2s with headers as they don't act the same as they do with stock manifolds. here is a quick screenshot of your tune and the settings im talking about. if your integrator delay is to large in the idle area it may not swing fast enough and go either rich or lean for a long time.

My thinking is since you're commanding PE via pedal position at 9 to 12% and you touch the throttle in the 2nd log (30% in the scan) :

pedal position is not a direct correlation to TPS. so 9 to 12% should not throw the ops car into PE. if you have 10% in the PE region for tps that is something like actually 40%. I cant exactly remember. plus in the ops logs never does he get over 1500 rpm and that is PE rpm enable set point so I highly doubt that is his issue.

[gmorris]

IMO I would have more timing at idle.

download a 09 corvette tune from the Tune Repository and go to

Fuel>power enrichment>pe throttle/pedal hot change those numbers to the tune you download to your tune

also go to EQ Ratio and change those to what you want the afr to be at WOT (14.7/your target afr= those new numbers in EQ Ratio).

also go to Enrichment Ramp In change that to 1.300.

My thinking is since you're commanding PE via pedal position at 9 to 12% and you touch the throttle in the 2nd log (30% in the scan) the car is going into PE and the enrichment ramp in at 2.000 means its dumping a shit ton of fuel. Your wideband show it going rich too.


your lean issue- go to your maf table:
2550hz to 2700hz in your maf table isnt right also this might be why you go lean. at 2550hz your at 93 then 2700hz its at 57 then at 2850hz its goes to 130. highlight 2550hz to 2850hz and smooth it till it looks awesome, same with the whole maf table.

Hope this helps, other welcome to tell me if I'm wrong

Thanks for looking but I checked the log again and it is not going into PE when I tao the throttle...afr cmd remains at 14.7 the entire time. Not sure why you're referring to the EQ settings...I already have it commanded to 12.5-12.8-13. It hasn't been fine tuned on the dyno but it should be safe and in the ballpark. The hot pedal values don't correspond directly to TPS...there's a chart floating around that show the relation and my settings are about 35% if I remember correctly. Actual is matching commanded as verified by wideband. The maf error has already been corrected...that was a tune I was playing with different MAF setting and didn't put it back to where it should be prior to uploading.

[gmorris]

OP first off I don't see your O2s being logged in the file you provided so its hard to get an idea of whats going on.

if they are not switching fast enough and its an a fuel trim swinging problem you may need to adjust your integrator delay, proportional base and airflow mode in the open & closed loop fueling. look for the thread I started O2 sensor tuning with headers. that is all about these setting ans getting the desired results out of my O2s with headers as they don't act the same as they do with stock manifolds. here is a quick screenshot of your tune and the settings im talking about. if your integrator delay is to large in the idle area it may not swing fast enough and go either rich or lean for a long time.

Thanks for the response...I've already spent a lot of time dialing in the o2's to what seems like the best compromise during normal driving but I will try dropping int at idle only. Not sure why you're not seeing o2 voltages because they are being logged?

[JBZ]

Thanks for the response...I've already spent a lot of time dialing in the o2's to what seems like the best compromise during normal driving but I will try dropping int at idle only. Not sure why you're not seeing o2 voltages because they are being logged?

weird that im not seeing them as I have them set up in my log. i see it in you channels though. you might try logging fuel trim learn on/off and closed loop active and that might tell you if its using the trims and if for some weird reason it kicking you out of CL into OL at the time of the event.

[schpenxel]

Log everything related to evap purge that you can and take another log of it happening

[gmorris]

I am logging CL status and it is remaining in closed loop the entire time.

[JBZ]

I am logging CL status and it is remaining in closed loop the entire time.

all i see is PE on off. here a screenshot of your list on the right hovering above mine on the left and the circled points are the ones i don't see you logging that i am refereeing to.

[gmorris]

all i see is PE on off. here a screenshot of your list on the right hovering above mine on the left and the circled points are the ones i don't see you logging that i am refereeing to.

I see what you mean...I just used Fuel System Status to tell me if it was going in CL. I added the others a swell.

I think I got it sorted...I lowered the 32 and below airflow mode cells in the O2 int and it is back to normal. I lost track f how high those were getting when I was increasing the int values for cruise, thanks for pointing that out. New log below.


06_23 idle 3.hpl

[gmorris]

I added some evap purge stuff but I've never dealt with any of that since this is a swap into a 69 chevelle with no emissions equipment.

[JBZ]

I see what you mean...I just used Fuel System Status to tell me if it was going in CL. I added the others a swell.

I think I got it sorted...I lowered the 32 and below airflow mode cells in the O2 int and it is back to normal. I lost track f how high those were getting when I was increasing the int values for cruise, thanks for pointing that out. New log below.


06_23 idle 3.hpl

awesome, glad I could help out