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Running rich, the saga continues
#51

I don't have any theories on the boost issue, I was just trying to propose a possible solution to the long running rich codes problem. I don't think the VAM has "failed", I think the VAM calibration is a bit too rich.

When you unplug the VAM then the strategy will determine the air flow based on throttle position and engine speed. I don't know how well the "speed-throttle" calibration works. If calibrated well, then the "speed-throttle" air flow signal could be good for some operating conditions. When the throttle is near closed and the pressure drop across the throttle is high, then the "speed-throttle" calculation can be good. Once the throttle is open and the pressure drop across the throttle is low, then the calculation is going to have problems. With a turbocharger and boost there will be a lot of guessing about boost levels and air flow.

If you unplug the VAM then the air flow calculation will change. I don't know what will be learned from the experiment. The "speed-throttle" strategy may work well in some situations but poorly in others.

On my vehicle I often have problems with the throttle position measurement changing. On my car the "speed-throttle" air flow signal might not ever be consistent.
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#52

(03-25-2024, 12:20 AM)TurboRay Wrote:  I'm no EEC expert, Dan ~ BUT...... couldn't he test that by simply unplugging the VAM and letting the computer default to the pre-programmed "limp-home mode", which (IIRC) is slightly rich & retarded, but driveable?? OTOH, I don't understand how incorrect VAM reporting would affect boost (??). <shrug>

I haven't checked this specific strategy but i couldn't find a "limp home" table in the LA3 file I have. I know the later EEC-Vs have a "load with failed MAF" (LWFM" table that makes the car run in Alpha-N. It's ok for part throttle, but any modifications from bone stock and it runs kind of crappy.

You could easily dial back the VAM output (without a tune) using a potentiometer, but adjusting fuel pressure is usually easier. If you're running really rich it could decrease your boost due to low EGT and incomplete combustion resulting in low turbo speed, thus less boost.

Confirming it was VAM related by datalogging airflow would be great, but I'm not aware of any datalog files out there for 2.3s. If there is one, I'd love to run it. Unfortunately I'm not ambitious enough to make one.

I read through the thread again and didn't see much mention of ECT sensor. But also I realized it closely matched my experience tuning mine. I noticed in mine on a stock tune it runs rich way too long, based on my wideband. Part of this I think is the coolant temp sensor locations in the intake manifold. I think they read colder than actual engine coolant out at the thermostat. If I didn't have the ability to tune I'd be tempted to relocate them to a manifold at the thermostat inlet. Instead I just had mine get rid of the ECT enrichment much sooner.

The other thing is the idle stumbles. I had lots of those, even with a clean IAC, new TPS, and idle adjustment. It would go pretty rich when coming to a stop, exacerbated by running too rich to begin with, leading to occasional stalls. If it was especially pronounced when the idle speed adder expired but it was still too cold to get to the base fuel table. The thing that solved it though was the RPM error for idle control parameter. It's only 50 RPM in the LA3 strategy, and I expect it's the same for others. Bumping that up to a much more reasonable 100 RPM made all the difference in the world.
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#53

Unplugging the VAM does not send the strategy into what is called "limp home" mode. The LA3 strategy has a Failure Mode Effects Management portion that re-configures the strategy to run as well as possible given the sensors that have not failed. For each failed sensor there is a work around to provide the best function possible with the remaining sensors.

The air flow map based on throttle position and engine speed is the LA3 Map at 30D4.

If the VAM reports too much air flow that could cause the air fuel ratio to run rich. Another problem with reporting too much air flow is that the spark strategy will retard the spark for a higher air load that does not exist. Reducing fuel pressure to reduce fuel flow will not fix the spark retard issue. Also, the fuel pressure is calibrated to provide a certain amount of fuel flow when the VAM is maxed out. Reducing the fuel pressure to reduce the fuel flow instead of trying to make the VAM reading more accurate is not the best solution possible.

When the fuel strategy goes into closed loop control using the oxygen sensor the ECT dependent fuel enrichment is no longer used. It does not make any sense to enrich the fuel mixture when closed loop fuel control is active. The rich mixture code 42 is only set in closed loop fuel control when there are no EGO switches for 15 seconds.
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#54

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LOL....... it sounds like both of youse guys (dan_xr4 & wickedsnake00) are well above my pay grade when it comes to EEC knowledge. I'm electronically challenged, and my "knee-jerk" suggestion to unplug the VAM was based solely upon the limited success that I've had when doing so on some of the MAF-controlled GM products that I've worked on in the past. <slaphead>
Placerville, California
(former)  '78 2.3T Courier w/blow-thru Autolite 2bbl carb ~ (current)  '87 2.3T Ranger w/PiMP’d EFI
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#55

(03-25-2024, 05:42 AM)dan_xr4 Wrote:  Unplugging the VAM does not send the strategy into what is called "limp home" mode. The LA3 strategy has a Failure Mode Effects Management portion that re-configures the strategy to run as well as possible given the sensors that have not failed. For each failed sensor there is a work around to provide the best function possible with the remaining sensors.

The air flow map based on throttle position and engine speed is the LA3 Map at 30D4.

If the VAM reports too much air flow that could cause the air fuel ratio to run rich. Another problem with reporting too much air flow is that the spark strategy will retard the spark for a higher air load that does not exist. Reducing fuel pressure to reduce fuel flow will not fix the spark retard issue. Also, the fuel pressure is calibrated to provide a certain amount of fuel flow when the VAM is maxed out. Reducing the fuel pressure to reduce the fuel flow instead of trying to make the VAM reading more accurate is not the best solution possible.

When the fuel strategy goes into closed loop control using the oxygen sensor the ECT dependent fuel enrichment is no longer used. It does not make any sense to enrich the fuel mixture when closed loop fuel control is active. The rich mixture code 42 is only set in closed loop fuel control when there are no EGO switches for 15 seconds.

I had to do some digging around to find out just what that Alpha-N map was called. In my definition it looks like it's called "VAF Substitute." Previous point still stands about how those maps tend to do fairly well- as long as everything is bone stock and working perfectly.

I agree with the point about how critical measured airflow is for calculating load, which is used for almost everything. My point was that adjusting fuel pressure is the quickest and easiest way to lean things out to test if that improves things. A couple of seconds versus a lot of work wiring or calibrating the VAM signal. Not a long term solution, but a quick A/B test.

I went looking in the stock 8UA strategy and it looks like the "Engine Warm ECT" and "Low ECT Fuel" threshold is 150F. I can only comment on my experiences but mine stayed rich well past that (at least relative to the cluster reported and thermocouple measured ECT), until I removed that enrichment earlier in the cold fuel table. But that may be neither here nor there.

I can only say good luck with the VAM calibration route. That's going to be a pain without datalogging capability. I wonder if you can get a MAF company to calibrate it? I can give you the table for what the ECU is looking for, but you'd need a flow bench to adjust it to match.
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#56

(03-25-2024, 12:07 AM)TurboRay Wrote:  
(03-23-2024, 09:56 PM)Milehighxr Wrote:   For now it looks as if I am going to be selling the car......

My guesstimate is that paint is gonna run me at least $10k, and probably closer to 15......

.. You may find it a "hard sell" to offload a car that runs poorly (running rich, virtually no boost, and unusual turbo sounds)!  <shrug>

.. No offense intended, Johnny ~ BUT...... IMHO, anyone who would spend 10 to 15 THOUSAND dollars to paint and repair the body on a $5,000 - 8,000 car should have their head examined!  <headslap>  My 2¢......

LOL, this is my FIRST  car Ray. Way back in 04-05 the guys I worked with at the time couldn't grasp why I was driving nearly 20 year old cars(my wife and I also had an 88 Merkur Scorpio). At the time I told them I would rather spend $20-30k on this car, than $20-30k on some cookie cutter car that looks like everything else, and has all kinds of crap that I don't want or need, such as airbags, abs, etc... If I won the lottery tomorrow(and ya gotta play to win, and I don't play) I'd happily wait 2+ years and restomod the car with modern power, and then enjoy her for the rest of my days as a daily driver like I wanted to. But plans change and life gets in the way...

Yes I do know a failed project is gonna be a tough sell. That's why I still don't have an ad up. I need to get all my mods and repairs all sorted and "on paper". My goal is to figure out what happened and possibly even get a passing smog test before I sell it. We'll see if it happens.
Johnny

86 XR
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