Idle AFR changing whilst Idling

[Terminal_Crazy]

I'm running out of ideas.
Since rebuilding the motor I've checked everything multiple times.
Pretty much everything is new except the pan and block.
It's had split BLM's and had O2 differences.
It's on it's 3rd set of injectors, 2nd set of NEW o2's

I'm pretty certain the manifold (Edlebrock LT4 performer was) passing air underneath, the ports were wet when i emoved it.
I've remachined it (bought a mill to do it) but not 100% convinced it's sealing the ports.
If I end up removing it I'll have to re mill it and cut down some of the larger sealing areas.

Exhaust leak is pretty unlikely, been over them many times, including the egr ports. ** Might just recheck the M22? plugs i fitted to the headers 9 years ago ***

Cylinder misfire possibly but Steveo's EEHack disdn't highlight any issue with the cylinder test which was straight after the uploaded datalog where the RHS has pretty much flatlined.

Odd how both sides drop around 300Secs and by 550 the RHS has recovered until 1200 secs when it starts to drop again.

Weird !

Thanks
Mitch

[spfautsch]

One of kur4o suggestions was cylinder misfiring - wouldn't that generally cause a rich condition when running open loop?

Are the m22 plugs you mention blocking off the AIR ports?

Can you reproduce this symptom from cold startup?

As you say this really is odd. I would think the lazy right narrowband reading could be indicative of an open heater circuit, but that doesn't explain the very distinct event around the 5 minute point in the graph that's clearly effecting the wideband as well.

[Terminal_Crazy]

One of kur4o suggestions was cylinder misfiring - wouldn't that generally cause a rich condition when running open loop?

Are the m22 plugs you mention blocking off the AIR ports?

Can you reproduce this symptom from cold startup?

As you say this really is odd. I would think the lazy right narrowband reading could be indicative of an open heater circuit, but that doesn't explain the very distinct event around the 5 minute point in the graph that's clearly effecting the wideband as well.

Hi
I think Misfire causes it to run lean as it measures the O2 content which has just jumped by 25-30%
The M22's block off the AIR ports (1 per header) ...seem OK

Reproducible with tonights log. The dip is there around 4-5 mins but isn't important as motor is only 50c then.

Not as odd as tonights log.
Does anyone want to have a laugh at this.

Checked the M22 bolts in the headers. Seemed OK, no blowing.

Previous: LOG a30 idle: RHS O2 sensor dropping LEAN & WB AFR rising to 16-8...

LOG a30-2_idle
Ran another idle test & used EEHack to play with the timing & AFR
Graphed with EEHack
Top graph AFR Target & Wideband O2 AC Pressure
Bottom graph Left O2 Oxy Sensor mV & Right O2 Oxy Sensor mV



Warmed up car on same bin till 90c | same as previous log
Both drop around 4-5 mins | No idea but not important as car is on 50c here
|
log @ 9k dropped 5 degrees timing 32 ish | no observed change
|
9k8 AFR 14.7:1 | Both O2's drop off the scale
10k2 14.0:1 | O2's pick up slightly
10k6 13.0:1 | as normal
11k 12.5:1 | better
11k5 12 :1 |
|
12k4 timing +5 degrees (37) | no real change
12k7 timing -5 degrees (32) | no real change
13.1 AFR 13.1:1 | both O2's bouncing about
|
15k1 cut cylinder 1 - flat lined BOTH o2's ??? |
15k2 cut cylinder 2 - flat lined BOTH o2's ??? |
15k3 cut cylinder 3 - flat lined BOTH o2's ??? |
15k4 cut cylinder 4 - flat lined BOTH o2's ??? |
15k5 cut cylinder 5 - flat lined BOTH o2's ??? |
15k6 cut cylinder 6 - flat lined BOTH o2's ??? |
15k7 cut cylinder 7 - flat lined BOTH o2's ??? |
15k8 cut cylinder 8 - flat lined BOTH o2's ??? |
|
16k5 Settling back |
|
16k6 AFR 9.1:1 | stable
AFR 10 :1 | stable
17k5 AFR 11 :1 | stable
18k AFR 12 :1 | slightly eratic
18k5 AFR 13 :1 | back to very eratic


Weird results, but I don't know what it tells me other than it likes fuel.

The only thing i'm aware of in the bin that's not correct is the Injector Flow rate I've lowered to 37 to scale the VE tables down.
Injectors are Now 42lb Bosch III Blue Demon (EV1 plug EV6 style) from FIC
Also had previously
30# VENOM Rated at 30 lbs/hr @ 43.5 psi
and (Bosch III FIC 312.6 / 10.2 = 30.64)

Why would cutting 1 cylinder flatline both O2 sensors or is 100 data logs not enough to recover ?

The two EEHack data files are in the Zip


Thanks
Mitch

[kur4o]

I need to see some cruising logs at constant speed, load to confirm some ideas.

[Terminal_Crazy]

I need to see some cruising logs at constant speed, load to confirm some ideas.

Thanks, I’ll post up the last run that I did tomorrow.

[Terminal_Crazy]

Thanks, I’ll post up the last run that I did tomorrow.

I've definately been fighting this since I built the motor.
I've uploaded the last 2 decent runs I did.
The bin used will vary slightly but I've only changed VE tables as I've been chasing the WB AFR up and down.


Thanks for looking

Mitch

[kur4o]

Still not sure if it is a mechanical problem, bad tune or a mix of both.
Do you have older logs with the other sets of injectors.

You got constant knock at lower loads. Mixed side intermitten lean condition at low load conditions.
I suggest you start all over with your tune. I can make a starter bin and work from there.
That way we can rule out the bad tune hypotesis.