This is a continuation of two threads regarding issues with a zz502 block, Brodix Heads and a $8d ECU. Running Full time Open Loop (or trying to)

Since the last threads, I removed the heads and had them checked. The fouled plugs in Cylinder Six was the result of no sealant on the rocker arm threads that enter the intake runners from the rocker arm galley. Machinist said heads in great shape, put sealant on them. Reinstalled the heads. As a result of a prior situation with the engine WBO2 showing extreme lean conditions after warming up. I made the following changes.

1. New fuel Pump
2. New Fuel pump strainer screen
3. New fuel filter.
4. Sent injectors off to have the flow tested (all passed)
5. Installed an AEM Fuel pressure gauge under the dash so I could monitor fuel pressure on the road

After installing the new heads, intake manifold and plenum. Started the engine. Set Fuel pressure at 43-44 lbs with the vacuum hose removed (WOT) With vacuum hose, about 38 psi at idle.

Started it, warmed it, idled rough. Took for a drive. About half way through, WBo2 pegged on the lean side. Driving was somewhat ok but surging at idle and low speed. Got back to the house, sitting in the driveway and the WBo2 came back on at Lamda 1.0 plus or minus a couple of pts.

Beyond being totally frustrated at how much time, money and such put into solving this issue, I am really out of ideas on what the heck is going on.

CSV attached if anyone cares to look.

Don
Williamsburg, VA

 

Do you trust that wbo2? What's the nbo2 reporting? What was your fuel pressure reporting? Was it rougher running cold than before? Is it possible the ecm causing a problem?

 

No, I don't trust the WBo2. From what I can determine, WBO2 sensors either work or don't. This one reads fine for a while, then pegs on the lean side, then back to fine. Pegged at lean can be doing 40 mph. I checked for exhaust leaks with a hose as a stethoscope and heard nothing. This is the same side as the number six cylinder that had oil draining in from the rocker stud. Perhaps the WBO2 sensor got contaminated and heat or something makes it change.

I am running full time Open Loop, but the CSV table has the NBO2 readings. I added them to the monitor for the WB in TP. Attached is a section of the monitor where speed, etc are pretty stable, yet the WB is going lean. The NB is dropping at the same time.

Fuel pressure on the AEM fuel pressure gauge in the dash is reasonably stable at 36-38 PSI. I have the regulator set at 43 psi at WOT (no vacuum on the regulator)

The ZZ502 apparently has enough cam to have some roughness to the idle. It was not back before at 775 rpm. Now at 850 and not a smooth as before.

I guess it could be ECU.

 

I compared the WB vs the NB in your data and something seems off... I understand the NB isn't accurate enough to report an actual AFR, but when the WB was reporting 18:1, the NB was reporting around 600 mV (I would expect the NB to be near 0 mV at 18:1, particularly since they're both on the same side of the engine). Elsewhere when the WB is reporting pretty lean (>16:1), the NB is showing well over 500mV still.

Also understood that you're in open loop, so the NB isn't really affecting how the engine is running. But again, the rich/lean trending I would expect to be consistent between the two O2 sensors.

The other thing I'm noticing in the data is that generally speaking, the colder the air temps, the leaner the reported AFR. In open loop, you're very dependent on the MAT table for fueling especially when your air temps are varying from ~114F down to 64F. Do you have any closed loop run data files?

Is your bin available to look at? You can send to ultm8z@yahoo.com if so....

 

So looking at the data some more...

I guess I'm not seeing the connection between MAT and AFR anymore necessarily...

The commanded AFR gets to a maximum of 15.28. So unless the ECM is reporting something differently than it's actually doing, it doesn't look like the ECM is trying to lean out the mixture as much as the WB is reporting.

Unless the injector driver is degrading with time (maybe it's getting hot in the ECM) and not driving the injectors as much as the ECM is commanding? IF so, that would be a ECM failure. I'm not sure if the main processor in the ECM sees what the injector driver is actually doing vs what it's commanding it to do? Or does the processor tell the injector driver what to do and just assumes its happening?

Sounds like a question for one of the gurus like RBob or 84Elky or someone else.

 

Elky has the data and I am waiting for his response. I have a back up ECM I could try

 

Before you do that, I'd probably buzz out the harness at the ECM connectors to make sure there isn't anything on the wires that could damage the ECM.

https://www.bosmobil.com/chevy-thunder/ecm-pinouts.html

If you scroll down to the 7730 ECM, it has the voltages on each pin for key on, key off, engine running.