I don't think I believe your 33% fuel trim. Your scanner may be telling you that, but that seems unlikely to me. why not

1 Post that catch code I asked for

2 tell us all the things that your fancy scanner is capable of logging. Ford certainly makes MAP sensor frequency available, but it also outputs MAP. I'd expect a high dollar scanner to be able to read that.

3 You seem misinformed about what the O2 sensor is doing. IF the system is in Closed Loop, and your 460 is almost NEVER in closed loop, then the voltage will swing up and down because the mixture is being commanded richer and leaner. When the voltage crosses 0.5V, then that is the perfect AFR. If you put in resistors, then it will never cross that voltage and so it won't tell the ECU anything.

4 If you want to know your actual AFR, then put in a separate Wideband O2 sensor.

5 Run all the ECU tests for KOEO, KOER and continuous fault codes. You can still have codes without a check engine light.

6 Measure your fuel pressure at cruise, at WOT, and immediately after you turn the engine off.

 

Easy there tiger, Don't get your nuts jammed in a socket here now, after all these forums are all about helping each other out aren't they? not pissing on another guy's tool box on what is thought to be lack of "fancy" scanners.
The way I see it is;

A. If the fuel system shows me 50 psi of pressure and the my "fancy" scanner is telling me the ecu is at 33 % fuel trim, my injector pulse width climbs to 28ms, the check engine light comes with a codes p0171/p0174 system @ limit lean right bank/left bank, I'm pretty sure that ecu is dumping a **** load of fuel int the combustion chamber at this time.

B. The last time I check the snap modis was one of the top diagnostic scanner out there, for info what you see is what you get, now if you know of some other way to access information from eecIV ecu via the diagnostic connector or the service port please enlighten me after all these forums are about learning and diagnosing.

C.If you take a close look at the second data sheet you will see that the feed back system is in closed loop roughly half the time witch would put it into open loop the other half the time so if my scanner is reading the opposite of what is actually happening it still would be in open / closed loop half the time witch is a normal strategy for a heavy duty emissions vehicle.

D.o2 fuel strategy, yes, you are correct the perfect mixture is achieved at the .5 a volt threshold (Stoichiometric ratio 14.7 to 1), the ecu is continually looking for the .5 v threshold, if it sees the system rich (high voltage) it will subtract fuel (shorter injector pulse and a negative fuel trim), system lean (low voltage) a (a longer injector pulse and positive fuel trim).
Now if you install a resistor in the o2 signal wire and lower that signal to 300mv the ecu will respond by adding fuel, once the ecu sees that it has added a maximum of 33% (this number varies from program to program) positive fuel trim and still has not achieved a cross count it will flag your p0171 system @ limit lean.
So in fact it is telling the ecu the system is lean "add fuel", and thus the whole theory on closed loop operation is based on.
The other part of these rich / lean pulses of exhaust is to aid in catalytic converter function, that's whole other topic but i'm sure there is plenty of reading out there on that subject,

E. To answer your question yes I have run multiple koeo, keor and continuous test no codes (besides the system lean code from my little experiment) and I have driven countless miles, idle and run koeo tests with a fuel pressure gauge mounted to my hood, fuel pressure is defiantly not an issue.
I'm curious about this catch code and what information you you can get from it, again eager to lean new
information, don't know if I can get the number to you before my trip i will do my best.

Just to shed a little light on the subject, I have removed all my add on mods, ect, iat, resistors for diagnostic purposes. I have also removed the after market throttle body and went back to the stock one, (no change). fuel pressure is set to stock specs. the problem was there before I installed the cam and roller rockers, roller timing chain and gears, eliminates that, that leaves the gale bank headers, and the 5:13 gears, psom was re-calibrated speedo is dead on.
The big clue I think is the vacuum @ wot, are the headers enough to confuse the ecu strategy? and why @ 3900-4200 rpm window ?

thanks, Dom

 

How are you getting codes p0171/p0174 with an OBD-1 system?
Those look like OBD-2 codes (p0).

 

The 1997 federal emissions truck went along for the ride with Californian obd II mass air flow system, the both use 3 digit "po000" codes.
Speed density systems can't flag right or left bank or post cat o2 sensors (only 1 o2 sensor is used on speed density), but it will flag system at limit rich or system at limit lean and other non specific codes.

If you have access to all-data or Mitchel on demand you can look up the codes (I believe some 1996 trucks do the same thing.

When I leaned out the o2 sensor to it's limit I got a cel and code p0171
Cheers, Dom

 

As you've split this up into multiple points, let's deal with them that way (and I'll probably do multiple reply posts so it doesn't get too long.

I'm not condemning you for not having a "fancy" scanner, I'm just say that SnapOn
makes some of the most expensive scanners out there, and if this is what you have, then it's not serving you very well. They also make inexpensive ones, but if I had the high dollar one I'd be asking for a software update to display Closed Loop correctly, and I'd want to display MAP in inHg and not the Frequency from the sensor. If you only had a $300 sensor, you'd just have to put up with what you had.
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OK, so now you're giving us some NEW information. The stock fuel pressure is supposed to be 39psi above whatever the manifold pressure is. As you're not supercharged or turbo charged (or you haven't told us that you are) then your fuel pressure is above stock. (Unless you are reading absolute pressure, in which case it's a tad low)

28mS is about right for full power though, so that's good.

Unless you've been changing ECUs then you have an OBD1 system and your codes do not have a P prefix. I could confirm that with the catch code, which is why I asked for it.

Conceivably your truck was made for a state that has a different calibration, like CA, MA, NY, but the catch code, and possibly your own location would help with that.

Assuming the most likely case, you do have OBD1, and if so, your codes are 171 and 174 which means something else from the definitions you posted. Also 2 O2 sensors on trucks are unusual except perhaps in California trucks. Again, catch code confirms.

 

If that is all the scanning data a high dollar fancy scanner can give, then I'm disappointed in it. Does it not have any updates to enable the other parameters?

If you were to get a Moates Quarterhorse on the J3 service port and a copy of Binary Editor then perhaps you could read many of the ECU internal parameters.
Whether you could or not depends on whether your catch code is supported or not. Another reason I've been asking for it.

So now in your latest post you tell us that Ca 1997 trucks can have OBD2. However the first line of your original post says

"Going to try this post here first, here's the scoop, 1997 7.5, 5spd, s/d system."

So you've said you have Speed Density, are you saying you also have OBD2? That would be surprising. Please confirm OBD1, with the diagnostic port under the hood.

 

I see it in different Open/Closed loop states in about half of your data frames. When you only post 25 or 20 frames, this should not be interpreted as half the time.

I have seen the programming code inside the ECU for a 460, both OBD1 and OBD2. Depending on your catch code, I may have seen your code. The ones I have seen don't spend much time at all in Closed Loop. Your posted data is consistent with that. But it would be helpful for you to post the catch code.

 

It seems to me that you believe that your O2 sensor outputs 0.5V at Stoichiometric, and 0.6V if the mixture is a little richer and 0.7V if it is richer again.

Is that what you've been told?

That is in fact true for a Wideband o2 sensor, but your ECU does not know how to read a Wideband sensor, it reads a Narrowband sensor.

With a narrowband sensor, if you lower your 0.5V to 0.3V, then the sensor will never indicate rich. If the ECU doesn't see the O2 sensor switching from lean to rich, then it will think the O2 sensors are not giving reliable data, and it will refuse to alter any fuel trim.

That would be a good explanation of you had a Wideband O2 sensor and an ECU that could use it.

However I seriously doubt that you do.

In fact the excursions between rich and lean are so that the Narrowband sensor can be observed switching. All a Narrow band sensor can tell you is that the mixture is rich or that it is lean. It can NOT tell you how much. The only way to find stoichiometric with a Narrowband sensor is to ramp the mixture up and down and observe the instant at which it switches. When you know the mixture at the instant of switching, you know you're very near stoichiometric.

So you're welcome to explain your resistor theory in more detail, but I don't see a resistor in the O2 circuit helping in the slightest.

I believe you have a code 171, and your fuel may be at its adaptive limit(and your scanner seems to indicate a big fuel trim). However Code 171 can also be failure to switch, possibly caused by your resistor. I suggest you take it out.

If you really do have a Code 174 (which is also unusual in a 460, but maybe in your catch code) then it is for slow HEGO switching. Possibly your resistor.

 

I would love chit chat and discus your interpretation of a closed loop system further but unfortunately I'm also Trying to pack for a week long camping trip with my family at the same time, as for the "point form literature" I believe that was your idea (see post #16 to refresh your memory).
I believe that when a discussion starts to balance on whether or not a 1997 ecc iv code has a "p" prefix, the dialog is getting a bit stale for my liking, anyways got make this short got things to do, and I would like to drive of into the sunset with my cheep little scanner to my favorite camping spot.
I did manage to get those numbers for you (they might be backwards) pretty tough to see with the cruise control in the way, HHXO EFI2D44D2 F6TF-15A650-BFA try that and let me know what you come up with, like I say I'm leaving in a few hours so you might not hear from me for a week or so.
It's been a pleasure,
cheers, Dom
ps: It's had this problem even before I installed the super charger (just kidding)

 

Your catch code is HHX0. This confirms for the rest of us what you may or may not already know, that

You have an OBD1 EEC-IV processor
Its error codes are Ford specific OBD1 codes and should not be interpreted as OBD2 codes
It can not generate a CODE 174, but it can generate a CODE 171
Like the other injected Speed Density 460s since 1994, the only time it enters Closed Loop is when the truck is coasting, which is hardly any of the time.
That means that coasting is the only operating point that develops any Long term fuel trims.
That means it doesn't adapt to component aging or fuels other than gasoline. So if you're running E10 as most have to these days, then you're already running 4.5% lean

Your tuning by resistors is what people tried to do before anybody understood exactly what was happening inside the ECU, and before they had any means of changing it. Better ways are available today.

You don't need to believe what I tell you about how your O2 sensor system works, but you DO need to go do some reading and work out what you are going to believe. Only then will you get anything useful out of it.

 

Yes HHXO F6TF-15A650-BFA is OBD-1 with map sensor and no P0 codes.







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