Where can I find the Sequence of Operation regarding what sensors (inputs) the ECM uses to switch from Open to Closed loop?

Specifically, my '92 F250, 460, A4OD (in my signature) runs great at initial start-up, and for the first 5-10 seconds, but then it stumbles a bit (30 seconds or so). My closest analogy would be that this is almost like starting an old carbureted engine with a closed choke, and then opening the choke too soon after start-up. Is it temp related? I don't know, but it doesn't do this on warm/hot starts, and after it gets over this initial hiccup it runs just fine.

I'm just starting to dig into this (no, I haven't checked the fuel pressure yet), but it doesn't set any codes, so right now I'm just looking for info on what parameters the ECM uses to switch from Open to Closed loop, as I have a sneaky suspicion....

And I do have the Service Manuals, but I haven't found this info in there.

Yet.

Thanks!

Jim

 

I have found this article to be very informative from the Old Fuel Injection site: Strategies

I think Ryan did a good job covering the basics of this vintage EFI.

 

I appreciate the response, and the link, and while it explains what the EEC does, and how EFI works (or how to set it up), I guess I'm asking for more of a detailed description, something along the lines of:

In order to go into Closed Loop, all of the following must be TRUE (I used to read a lot of Control Codes for HVAC equipment in a previous life):
* IAT above "X*"
* Coolant temp above "Y*"
* Oxygen sensor temp above "Z*"
* TPS value < "A" and > "B" VDC

That sort of thing. Always makes for really dry reading, but I've fixed an awful of HVAC Controls by reading Functional Spec's like these.

I'll be sitting down with the Manuals I recently purchased (all hard copies) over the next few evenings, and I'm really hoping to find something like this.

 

It seems in my experience with tuning on this vintage EFI that the main trigger for the transition from open to closed loop is engine coolant temp, there are variations on the exact temp used but in general the average coolant temp has to be up into the area where the thermostat will soon open... like 130-140deg F. The amount of time it takes to get there will depend on a lot of factors including engine displacement and atmospheric temp, but in general I think it takes more llike a minute to get there in most cases from a dead cold start. But on top of that all engine sensors must be reporting and be in what is considered to be a normal range with the exception of the O2 sensor which is ignored at cold start.

 

Yeah, funny you should say that, as I just picked-up a new coolant temp sensor (and O2 sensor) at NAPA today. The truck also has a 160* stat in it (based on the receipts that came with the truck, plus the indicated temp on the gauge), and I've had a 195* stat and gasket rattling around in the glove box for a couple weeks now, just waiting for the time to put them in. (The O2 sensor is for an old issue that pops-up every so often, not for this one). I'm hoping to lay some hands on the truck this weekend, but only if "SWMBO" hasn't already made plans for me!

We'll see....

 

Checkout some videos on YouTube, they can explain it much better in a video

 

Best answer to your question is
The oxygen sensor is the switch
Basically, all the sensors are on line and they all wait until the O2 sensor heats up
When the O2 sensor hits 600 degrees or so, it starts generating a voltage signal
That is when the closed loop operation starts
That is why newer O2 sensors have heaters (to speed up the process)
I can maybe post a page or two of Ford service literature about open VS closed loop operation

 

Interesting! And I mean that!

I've been living with an oddball code that calls-out the O2 sensor (KOEO code 41), but I just haven't gotten around to doing anything about it yet. When I looked-up this code I saw something along the lines of "O2 sensor on the RH bank" (emphasis mine), but when I finally got around to crawling under the truck recently (I didn't know if it was a 3-wire or 4-wire), I only found only one O2 sensor, located at the end of the y-pipe, right before the catalytic converter on a "crossover pipe" running between the left and right banks (460 engine, dual inlet converter). I did buy a new O2 sensor at NAPA recently (Echlin), and it's supposed to be nice here this weekend, so I'll get this installed sometime in the next couple days.

And while I didn't find the Sequence of Operation in the Manuals I recently purchased (link to that post: https://www.ford-trucks.com/forums/1...t-to-work.html ), this morning my wife reminded me of a pretty thick (7"-8" thick) Ford book with all sorts of tabs in it (shop manual?) that I also bought at the same time. However, that one smelled pretty bad when it showed-up, so it's in a closed-up box in the basement with 3-4 boxes of Arm & Hammer Baking Soda to hopefully "de-stink" it. I don't recall that exact name of it, and I'm at work right now, but I think this may have the info I'm looking for. If not, I'll shoot you a PM.

Thanks!

Jim

 

The reference to Right Hand Bank denotes the passenger side of the vehicle. It is a reference from sitting in the driver's seat. You are correct there is only one O2 sensor on your truck, that is typically located near where both down pipes converge (V8 engines) on the passenger side. The primary O2 sensor will be referred to as RH sensor.