AFRs are erratic and drifting rich

[silver_cobra_01]

The car was in storage for a while and finally took it out a few months ago only to find out it wanted to idle at 11.5-12 AFR. Nothing had changed since I first tuned it so very strange. Thought that one or more of my Siemens Deka 80S was stuck open or partially open so sent them out to be cleaned. Reported back with "cleaned multiple times due to erratic performance" but ended up being within 5% of each other so I ran them. Same issue. Idle and cruise around 11.5-12. Thought maybe the wideband was bad so replaced it. No change. Figured that the 80s were still "performing erratically" so I bought FIC1000s, adjusted the tune, and same thing.

The most notable oddities of what's going on is that the car will crank, start, and be extremely lean, 19 or so, for the first minute or two of startup then slowly work its way down to 14.5 or so. Then, let the car sit for an hour or so, and again startup was lean, but now around 16-17 and after a minute or two worked down to 13 or so afr.

Recently replaced all COPs with FRPP, plugs with TR6s, and both front O2 sensors

I'm now thinking the ECU might be bad but I'm open to any ideas, suggestions, or opinions anyone else may have. Thank you for your help guys.

 

[silver_cobra_01]

Just went out and started the car again. This time it sat for about two hours. Started up around 15-16 afr and worked its way down to 12 after a minute or two.

 

[MG0h3]

A failed ECU is extremely rare.

Are you getting codes for rich? Any way to monitor your O2s?


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[silver_cobra_01]

No check engine lights but it only has idle time, no driving. It's open loop so not sure if I can log O2s but I'll go see if I can log voltage and come back.

 

[03cobra#2]

Can you log the wideband into livelink through your xcal4? So that the AF shows up in livelink....that is key in seeing what the af does in relation to the short term fuel trims.

If you can get a log of engine rpm, af, stft's, spark, spark source, fuel source, maf counts, idle integrator, isc duty cycle, coolant temp, load, and injector duty cycle, and the frps so we can see delta fuel pressure.

Log a cold start steady idle for like 2 min, the get the car up to operating temp and log a steady idle for 2 min.

Post up the logs and see what we got.

 

[silver_cobra_01]

A failed ECU is extremely rare.

Are you getting codes for rich? Any way to monitor your O2s?


Sent from my iPhone using svtperformance.com

O2 voltages were around 0.45-0.5 after about 5 minutes of idling. Took about 2 minutes for them to get to 0.15-0.20. I'm not sure where they should be but I'll do a quick google.

 

[silver_cobra_01]

Can you log the wideband into livelink through your xcal4? So that the AF shows up in livelink....that is key in seeing what the af does in relation to the short term fuel trims.

If you can get a log of engine rpm, af, stft's, spark, spark source, fuel source, maf counts, idle integrator, isc duty cycle, coolant temp, load, and injector duty cycle, and the frps so we can see delta fuel pressure.

Log a cold start steady idle for like 2 min, the get the car up to operating temp and log a steady idle for 2 min.

Post up the logs and see what we got.

Right I'm logging in livelink. I'm currently tuning open loop so no stft's. As far as I could tell, injector duty cycle isn't available on my ECU (MSE3) if anyone knows otherwise let me know. I'll log a true cold start tomorrow. I could turn closed loop back on for stft I suppose but I don't necessarily think I would want the O2 sensors compensating for whatever is going on.

 

[03cobra#2]

Right I'm logging in livelink. I'm currently tuning open loop so no stft's. I'll log a true cold start tomorrow. I could turn closed loop back on for stft I suppose but I don't necessarily think I would want the O2 sensors compensating for whatever is going on.

You can keep open loop on. Probably just need some cold start enrichment & maf transfer tweaking.

 

[silver_cobra_01]

You can keep open loop on. Probably just need some cold start enrichment & maf transfer tweaking.

The lean start up is on both cold and warm starts. As far as I can tell, the Startup Cold Fuel table shouldn't be used until temps drop back to 110 in my tune.

I've leaned it out with the MAF a couple times. With the FIC1000s it was first idling at 11 or so. Reduced MAF in the appropriate cells by 10%. Idled at 12. Trimmed another 10% and idled at 13.5. Trimmed another 5% then it idled lean at 19. So then I richened it back up in 4% increments until it idled around 14. These were all done fairly quickly together, minimal time sitting. Then I ate, came back to the car, and realized that it seemed to be running richer after letting it sit.

Either way, I'll log tomorrow and see what you guys suggest. Thanks for the help.

 

[03cobra#2]

Yeah. Just make sure it's up to temp. 180-200 ect and let the idle stabilize for at least 2 min... Then you'll get accurate af reading. Letting it idle for 2 minutes undisturbed without touching the gas pedal is key before taking and af readings.

It's normal for af to be high or low and then eventually settle / stabilize after awhile while in open loop.

 

[01yellercobra]

I don't think that's enough range on the narrowbands, but being that you're running open loop it shouldn't matter. Its been a while since I've measured them.

Are you running big cams? If not I would turn STFT's back on and see how they compare to your wideband. Also, you can't adjust the MAF transfer when the engine is cold. It needs to be fully warmed up.

MSE3 is for an 01 right? I don't remember mine having injector duty cycle.

 

[silver_cobra_01]

I don't think that's enough range on the narrowbands, but being that you're running open loop it shouldn't matter. Its been a while since I've measured them.

Are you running big cams? If not I would turn STFT's back on and see how they compare to your wideband. Also, you can't adjust the MAF transfer when the engine is cold. It needs to be fully warmed up.

MSE3 is for an 01 right? I don't remember mine having injector duty cycle.

No big cams. I can go back to CL to log STFTs.
The adjustments I made to MAF were at operating temp. 190-200.
Correct MSE3 is 2001 cobra.

Yeah. Just make sure it's up to temp. 180-200 ect and let the idle stabilize for at least 2 min... Then you'll get accurate af reading. Letting it idle for 2 minutes undisturbed without touching the gas pedal is key before taking and af readings.

It's normal for af to be high or low and then eventually settle / stabilize after awhile while in open loop.

Right, the af readings I've been making changes off of has been after three or four minutes at full operating temp. I remember it taking time to settle in but I don't think it should take multiple starts and make such drastic swings in af, especially dropping a full point on multiple start ups.

 

[silver_cobra_01]

Here is a log of a warm start, 150 or so startup temp. It has more than you asked for but let me know if anything stands out to you guys. I'm sure I'll still grab another one tomorrow. Thanks.

 

[03cobra#2]

Idle don't look too bad. Couple things. After a couple minutes it looks like your af stabilizes around the 12.5-13 range.

Im not sure how to decipher the maf counts as on my logs it's called maf ad counts. When looking at maf ad counts it reads the number that corresponds on the maf transfer table. Anyway, I would subtract a bit of fuel from your maf table at idle. Maybe take 3-5% away and see how it does.

I really don't see your AF swinging all over the place. Again after a couple minutes of warm idle af is steady.

Couple other things. Once you get af closer to 14-15 at a warm stable idle your idle air integrator needs a bit of work. It is reading -.35. It should be closer to 0. A quick Google search will say how to correct that. After those parameters are good you can try lowering idle spark..... If idle seems a bit rough and / or won't settle down to 800.

 

[silver_cobra_01]

Idle don't look too bad. Couple things. After a couple minutes it looks like your af stabilizes around the 12.5-13 range.

Im not sure how to decipher the maf counts as on my logs it's called maf ad counts. When looking at maf ad counts it reads the number that corresponds on the maf transfer table. Anyway, I would subtract a bit of fuel from your maf table at idle. Maybe take 3-5% away and see how it does.

I really don't see your AF swinging all over the place. Again after a couple minutes of warm idle af is steady.

Couple other things. Once you get af closer to 14.0 at a warm stable idle your idle air integrator needs a bit of work. It is reading -.35. It should be closer to 0. A quick Google search will say how to correct that. After those parameters are good you can try lowering idle spark..... If idle seems a bit rough and / or won't settle down to 800.

The units for MAF here are volts. Your transfer function should have that in the third (?) column.

The first thirty or so seconds is 15-16 afr then transitions down and stabilizes like you say. I will make a 5% change and log again. The biggest issue that I see is that it drops a whole point or so after sitting and starting back up again on the same exact tune. I'm hoping I'll be able to grab multiple logs tomorrow to show this.

As far as idle integrator goes, there was only about fifteen minutes of run time on this tune so I'm not entirely sure its "settled in" to anything useful yet. If you graph it, it is rising the whole time, starting around -0.5 and ending around -0.2. I suspect it will keep increasing with more run time.

more logs to come.

 

[03cobra#2]

Looks like your on the right track for a good idle. Also keep in mind when your in closed loop the ecu will be able to smooth things out once your AF is in the ball park. Always a good idea to re-enable closed loop to check your progress. Stft's should hoover around 1.0 plus or minus a bit.

 

[MG0h3]

O2 voltages were around 0.45-0.5 after about 5 minutes of idling. Took about 2 minutes for them to get to 0.15-0.20. I'm not sure where they should be but I'll do a quick google.

Your O2s are reading lean.l for whatever reason Telling PCM to add fuel. Obviously you aren’t lean based on the wideband

They range from .1-.9. Lean to rich.


“BLM is doing God’s work”
2KblackGT

svtperformance.com mobile app

 

[silver_cobra_01]

Your O2s are reading lean.l for whatever reason Telling PCM to add fuel. Obviously you aren’t lean based on the wideband

They range from .1-.9. Lean to rich.


“BLM is doing God’s work”
2KblackGT

svtperformance.com mobile app

I'm in open loop so the O2's shouldn't be affecting the commanded fueling but it sure seems like it is. The front O2s have already been replaced. Assuming this is the issue, do you have any suggestions on troubleshooting or fixing?

I'm hoping I'll be able to get multiple datalogs tomorrow to show that the same tune is progressively running richer on after each start.

 

[01yellercobra]

It might seem extreme, but try writing another quick tune and loading it. See if things act normal. I've had a tune go wonky while adjusting things. I ended up starting over on that one.

 

[silver_cobra_01]

Didn't end up having much time to play with it today but I was able to get two logs. Both logs are the same exact tune, the car just sat for about two hours after the first was taken. The first log is shorter and unfortunately didn't include a cold start but it does show the stabilized idle and AFR. At the end of the first log it was running around 13.9-14.2 or so. The second log is longer and did technically include a cold start since it ran off the startup cold fuel table. At the end of the second log it was running around 12.8-13.1 or so. The actual AFR obviously varies but hopefully the data will do a better job explaining the issue. The best way I can describe it is that the car just drops a point or so in AFR after sitting and starting back up until it reaches 11-11.5 AFR. I will try again in an hour or so to see if this happens again like it did last night.

Tbh I'm not sure where exactly to go from here but keep looking over the tune. Maybe there is some parameter I didn't notice that created this affect, but I did more or less follow the same process I used when I tuned the car a couple years ago.

If anyone has any suggestions please feel free to let me know. Thank you.

Edit: log2 was too large to upload so I've split it roughly in half