lakeffect2

I have an lean condition during during warm up. Yes it really does go into the 16-17 range. I don't seem to be able to correct it by changes to effect a richer open loop warm up experience. As you can guess it is not idling well, and forget about touching the throttle, as it only goes leaner.

lakeffect2

No ideas out there?

RBob

iTrader: (1)

There is the choke AFR and the AFR vs CTS multiplier tables to work with. The choke AFR decays out in 2 - 3 minutes after a cold start. The AFR vs CTS table is always used during open loop.

Fuel pressure OK when cold?

RBob.

Ronny

iTrader: (1)

How about adding a higher value in the VE table at that rpm/map you experience the lean condition?

lakeffect2

I'd thought of doing something like that Ronny, but when it goes into closed loop, "most" of the lean problem goes away. Some other lean issues are related to slight TPS movement, but in theory, it's a different issue.

Ronny

iTrader: (1)

BUT when the lean issue goes away at onset of CL do the BLMs or INT rise to 160? If so that indicates the VE table needs more fuel.

lakeffect2

Thanks Ronny. I'll do a data log on the way to work today.

lakeffect2

After a rebuild for rings, The system no longer goes into closed loop, and open loop shows lean in the 17-20 range. Checked fuel pressure, brought it back to 44lbs but still lean and no closed loop.


Dave

RBob

iTrader: (1)

See the new thread you opened for this issue...

RBob.

lakeffect2

Onw other question about something stupid I did.

I noticed that the O2 mv keep getting less and less, VE learn adding 12% everywhere (maxed out) It went grom 800 down to less than 100 over the course of several minutes.
I realized after ward, that I did not reset Hghway Mode to a high MPH value (200mph) before I did the VE learn

Is this likely to be the cause of the dropping O2 mv value?

Many thanks for you responses.

Dave

RBob

iTrader: (1)

It may, not probably not. In BLM VE Learn mode the ECM drops out of closed loop & BLM learn and the WUD will also not learn during this time.

In WB VE Learn the WUD compares the commanded AFR with the WB reported AFR. And bases the changes on the difference between them. Check the data log to see what the difference in between the two.

RBob.

lakeffect2

I found part of the issue.

I could not pull a vacuum with a hand pump on the fuel regulator. Additionally, when clamping off the return line, fuel would drop quickly, would not hold for more than a few seconds at key off.

Pulled the regulator, looked pretty beat. Since I've never changed it before, it was likely original from the 90's Afterward, retest would pull vacuum.

In for an inch , in for a mile, pulled the injectors to test if hung open . Made y own test unit with a battery, a stock TPI pump that I had before I put the 255 L/hr unit in, a piece of hose clamped to the pump (and injector to be tested) a GM injector pigtail,two momentary contact push buttons from radio shack and some wire. Turned on the pump, let pressure build for a few seconds, fire the injector.

No problem with injectors. Still have to dial up more pressure on the regulator to get 44.

lakeffect2

Regulator is now set at 44 lbs pressure. this seemed to help cure my global lean issues greatly. I'm actually looking at my EBL VE learns and seeing some negative numbers, not all+12 across the board. So I know I'm in the ballpark now.

RBob

iTrader: (1)

You're making headway, mechanical issues will bite you every time. Been down that road before and see it in others cars.

RBob.

lakeffect2

After a few more burns it's actually gettbng inder control again.

One area of concern is to try closed loop idle rather than open loop (after warmup) due to idle afr's in the 13.2-13.4 range . there is a box to check on one of the option words, but I'm not sure which status is which. Do I check to use VE tables in closed loop or uncheck?

RBob

iTrader: (1)

Un-check the forced open loop option flags for closed loop operation.

RBob.

CORV3TT3

In my opinion... if you are close to your targeted AFR for open loop at idle you're really close to being able to get closed loop at idle.

Pay close attention to your WB readings and your NB readings. Get very familiar with how it behaves in closed loop at idle.

Seriously... get very, very familiar with how your car idles, what it likes, and what it doesn't.

Not sure what calibration you started with, what your cam is, etc... but my personal experience has been that I needed to adjust the O2 windows at idle.

I arrived at that conclusion by studying the behavior of the car during idle (how it ran) and then confirmed with data (AFRs, swings, highest AFR when lean, lowest AFR when rich). It was the behavior- confirmed by data- that pointed to adjusting the switch points.

For me, it did take some dorking with the 02 switch points to get to the sweet spot. If you find you need to run the max lean/rich a little wide to get it smooth you can do that. With my cam, its not uncommon to see a swing of a 1/3 of an AFR in either direction during open loop and be happy so I replicated that in my O2 windows. It's really whatever your engine needs to be happy.

I run a little rich at idle (I wobble between and occasional 13.8 and a max of 14.7:1 with an average of 14.4) and then handrail it really close to 14.7for closed loop operation (max rich around 14.2 and an occasional max lean at 15.1 as it cycles).

lakeffect2

Sounds like i might need to learn more about O2 switch points. One the the ealy problems at the beginning of this thead was watching the O2 mv go from 800's to less than 100 over several minutes. I haven't been back to data logging to see if that got changed for the better, worse or same.


Corv3tt3's point of O2 switch points brought my O2 mv values back to mind.

For the record , I started with the EBL 3005 bin for highly modified engines. It's shown below in the signature.

lakeffect2

Back to lean everywhere again for no apparent reason. Will check fuel pressure in the morning, wondering if the regulator set screw has wiggles loose, or is gone entirely.

What littlerunning that does occur is back to afr's of 18-20 again, stalls with any throttle,tyat is if it starts at all.

lakeffect2

I believe I have tracked down the source of the lean problem. I have a Walbro 255l/hr pump that is going south. I was troubled by open loop lean issues, no start issues, AFR's pegged at 19-20. I was working with the fuel regulator , trying to get some pressure built, and realized the whirl of the pump was abnormal. no ability to get much pressure beyond 20 lbs.I
So looks like I'll be in the tank this weekend.

lakeffect2

AS a long over due addition to this saga, it wasn't the pump. I discovered there is a difference in the bottom contour of fuel regulators from different manufacturers and sources. Some are flat bottom, while some have a beveled edge. I could not hold pressure with the beveled version. Apparently fuel gets past the bevel.
I tested by clamping off the return line. Pressure held to 60 pounds, so the pump was working, and the check valve on the pump was holding pressure after key off. Released the clamp, couldn't even hold 40 lbs and at key off, pressure dropped within seconds.


I installed the flat bottomed diaphragm and retested pressure was maintained at 44lbs when the clamp was released. Big difference all due to the shape of the bottom of the diaphragm.