Fun with MAF's :-(

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budwich

Well-Known Member
thanks...
I did see that thread on the other site.
I am not sure that I am chasing bad mileage as it depends on the type of driving... around town in the "big city", I get about 6km/l (not sure what units people would use but that what I have from the DIC). On the highway, I see around 9-10km/l at about 100-110kph. My LTFT is near / at 0 unless significant throttle is applied. STFT "flutter" around +2,-5 or so again depending on throttling and such.

The one thing about my previous post, is the engine was high at cold start. This appears to be related to the fan clutch. For some reason, at various cold starts, it remains engaged for about 2-3 mins of the journey. So in this case, once engine was on a bit (journey was underway), I could that at idle speeds, the engine load was more in expectation of 20-25%.

Anyway, I am trying understand what "engine load" is and when and why it is at certain times.
This time at idle / cold / warm and also at higher throttle (40%) so when towing and causes the system to kick out of closed loop which I now suspect is potentially an engine load somewhere near or about 90% (don't know what the upper limit is).

PS. the thermal clutch is about 1 year old (acdelco) so I will likely try get a warranty on it ... of course, I get to do my effort on the switch out for free... :smile:
 

MRRSM

Lifetime VIP Supporter
By Definition...

"Engine Load"

Is ANY Resistance to Rotation created by the Engine Rotating Assembly that either Impedes or Slows Down its Steady State of Energy.

If that otherwise "Dis-Engaged Fan Clutch" was doing its Job by Doing NOTHING... it would NOT be "Draining Power" by behaving EXACTLY like a "Wind Mill"; invoking Air Resistance built into its very design to Grab and Draw in Air under the FORCE, starting with the Harmonic Balancer at the Nose of the Crankshaft as the Center of Rotation... Churning with no small amount of struggle against the Ribbed Serpentine Belt Clockwise and eventually wroking the OTHER items that resist ist power... the Water Pump, Alternator and A/C Compressor, placing an undue Burden at Idle as it Creates a Very Substantial Amount of Additional Drag on the System.

If you've watched a most recent Video from a New Member who complained of that "Jet Engine Roar",and a Reduction in Engine Power as a Direct Result of the FAN Engaging unnecessarily... You can see just how REAL Air Resistance at 14.7 PSI can be at slowing down or stopping the Engine from quickly elevating its RPM and allowing the Torque Converter and Transmission Fluid Pump to have enough Energy to Shift the Hydromatice Transmission through the Gears. The Blades of that FAN are No Different than the Sails on a Three Masted Schooner!

When this Phenomena happens. AT IDLE... The PCM has NO Choice but to Compensate by adjusting for any additional demand placed on an Engine ... no matter how slight that resistance may seem...when ordinarily... The Motor should only feel the slight resistance created by the Free Fluid circulating inside of the Inner Torque Converter when either in Neutral or Park.
 
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budwich

Well-Known Member
I wasn't able to correlate much between "engine load" and when the system drops out of "closed loop" into "open loop - engine load". I guess I am not monitoring the right parameters as "engine load" was all over the map in terms of value at "drop out"... from mid 80's to upper 90's. Perhaps it has more to do with advancement which I haven't been monitoring. Anyway, the system with the replacement MAF and replacement MAP is running "predictable" so I am probably just chasing a "learning curve" as in my learning curve as opposed to the PCM.
 
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budwich

Well-Known Member
well, the fun continues. Not so much so with the MAF but more on the general engine operation / air / fueling controls and "interrelationships" which I admit, I know little about in terms of depth.

So, with my monitoring of engine load (which I could find no obvious correlation to open / closed operation even though the PID displays "engine load" as the "excuse" for falling out of closed loop), I decided to add the "timing advance" pid figuring that perhaps I crossed a timing "threshold" (ie. too advanced) that may be caused the dropping out.

Well, that seemed to open a "new can of worms". wth... watching the timing with little throttle changed (20-25 %), it jumps to 30-35 degrees advance.... WHAT!!! it moves back down to a "nice" 5-10 degree as the vehicles continues to move. Medium throttling bring the timing to 15-20 degrees and once the speed stabilizes, again moves down to a normal 10-15 or so. At idle, in gear, it is sitting around 5-7 or so.

So the "erratic" response at slight throttle seems very unusual. On old vacuum based systems, I don't believe you would see such response, may be at hard throttle. Of course, I am not really sure what to expect. Anyone have some thoughts or pointers on this operation?
 

Blckshdw

Moderator
I do have the timing advance on my display too, but I haven't paid much attention to what it does under acceleration. Don't think I've ever looked at it, other than when idling. If I can remember to, I'll try and observe its behavior on tomorrow morning's commute.

I did have a random time where the fuel status dropped out of closed loop, after already being up to temp for 10+ minutes. I was coasting towards a red light, happened to look down at the engine load (remembering this thread) and it changed at that moment for maybe 2 seconds, then went back. :confused:
 
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budwich

Well-Known Member
sorry to hear about the "drop"... :smile: I hope I ain't causing any "anxious moments"... not my intent, more just trying do some "black box learning".

On your "dropout", the cause is usually shown also... note that the PID cause pairs "engine load" with "deceleration" so yours might have been a "appropriate event".... of course, I don't understand why. My "drops" have been on load (ie. going down the road under power).

Its all probably "innocuous" but since I know nothing past the numbers themselves, I am just looking for further depth of knowledge / experience.
 

Blckshdw

Moderator
When diagnosing a bad water pump a couple months back, I thought I heard some faint noise in the top end. Since it was following on the heels of a tranny replacement, I have been paranoid. My MPGs haven't been great, but on this last tank, I was in the low 15's, up from the 13's I'm used to. I'm thinking that's because it's summer, school's out, and traffic moves smoothly.

I had been keeping an eye on fuel trims, O2 sensor behavior and such. Everything seems pretty normal, from what I've seen posted in other threads, so no anxious moments, at least for the time being. 🤞
 

Blckshdw

Moderator
watching the timing with little throttle changed (20-25 %), it jumps to 30-35 degrees advance.... WHAT!!! it moves back down to a "nice" 5-10 degree as the vehicles continues to move. Medium throttling bring the timing to 15-20 degrees and once the speed stabilizes, again moves down to a normal 10-15 or so. At idle, in gear, it is sitting around 5-7 or so.
So at idle, my timing advance sits on 16 or 17 degrees. Under light throttle (driving through the neighborhood with speed bumps) it would jump up to 23 degrees, then settle back down. When getting on it a bit more aggressively, it would get up to 33 degrees for a bit, before coming back down. Once the vehicle was up to temp, the behavior didn't change. Never saw the timing get below 16 degrees. :twocents:
 
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budwich

Well-Known Member
Well... that's an interesting "data point". I would say that potentially is an expected kind of operation... based somewhat on "old car running". Now you got me wondering about the Cam sensor / solenoid. It was changed about 2.5 years ago. The old unit didn't look "bad" (ie. plugged screen or otherwise) but I thought perhaps it was time with mileage nearing 200kkm at the time. In the "old days" distributors and rotors / points would be a regular maintenance items and based on discussions herein on the cam sensor, I thought it was a good time. I still have the old one. I might throw it back in and see what I see ( plus that gives me an opportunity to check the screening on the current unit).

The one thing about your observation was the "never seen anything below 16".... seems somewhat "different" as I would have thought "normal idle" for most engines to be around 8-10.

Of course, its somewhat water under the bridge so to speak as I am not seeing any misfires as you are probably not either. IF there was a timing issue (even small), I would think that some counts would show up along the way.

Thanks again for the effort and "visuals".
 

Blckshdw

Moderator
I used to keep the misfire counters on screen, but there would be cases where 1 cylinder would report double and even triple digit misfires in a short amount of time, yet the engine would be running normally. It would never be the same one, so I ruled it as a misread by the app, since I have that weird issue with the transmission temp reading, coming and going.

One thing I added about a week ago, since I came across it, was the knock counter. It almost always says 94. Sometimes it will be null, once I saw it report something in the 80s. I don't know enough about it, to know what that means (yet)
 
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budwich

Well-Known Member
hmmm... I can say that I haven't seen much in terms of misfires as I only scroll thru the PID management area to current values and have rarely seen anything but a "1" here and there on the cylinders.

As you indicate, IF you were getting significant values, the vehicle would "feel it" and / or you would get "check eng" flashing at times.... it is quite possible torque / the interface / air potentially gave some funny readings.

I am going to pop up the knock counter to see what's up there... just for fun. overall, the vehicle runs fine / smooth but after playing with exhaust manifold removal and other things (o2, maf, map), I started wondering more about what's up... especially sometimes I see the upstream o2 get erratic at strange periods but not impact the engine "feel"... but then also causes "strangeness" in the downstream which I assume is the result of the upstream "strangeness"... it doesn't last long but periods of 3-5 seconds pop up here and there especially around low speed / just off idle, hence the "funny" around timing advance which to me seems significantly advances (30's).... but somewhat settle a bit as the engine warms (warmer oil may be helping the cam sensor out).

PS. can't find the Knock counter in the available pids, only knock retarder (in degrees). I see it in the excel spread sheet of extended gm pids but I don't see it when I go to add a display.
 
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