Ken:

Got the new scanner yesterday! Initial results from novice user shows a lean condition without any trouble or pending codes. Unless it's when it triess to go over the max limit which it's at alraedy! Not sure about anything right now.

It takes several key presses to do anything because it's all menu driven. It takes a few seconds to get "ready" to scan and another key press to start it. Too bad it don't have a quick scan mode with one key press.

I can't get the PC Link to find my Comm port either! Already emailed them.

 

Bill,

I'm sure once you get things setup and have a chance to play with it a bit you will start getting good information.

Ken

 

Ken:

Let me explain a bit better.

The Short/Long Term Fuel Trim 1/2 show -100 which I read is the max limit for adjusting for a lean condition. That was with a warm engine at idle. I might want check a good engine too.

 

Bill,

I thought you might find this interesting.

Ken

Fuel System Monitor
The Fuel System Monitor is an on-board strategy designed to monitor the fuel trim system. The fuel control system uses fuel trim tables stored in the PCM's Keep Alive Random Access Memory (RAM) to compensate for variability in fuel system components due to normal wear and aging. During closed-loop vehicle operation, the fuel trim strategy learns the corrections needed to correct a "biased" rich or lean fuel system. The correction is stored in the fuel trim tables. The fuel trim has two means of adapting; a Long Term Fuel Trim and a Short Term Fuel Trim. Long Term relies on the fuel trim tables and Short Term refers to the desired air/fuel ratio parameter "LAMBSE". Both are described in greater detail in this section under Powertrain Control Software, Fuel Trim. Input from the ECT or CHT, IAT, and MAF sensors is required to activate the fuel trim system, which in turn activates the Fuel System Monitor. Once activated, the Fuel System Monitor looks for the fuel trim tables to reach the adaptive clip and LAMBSE to exceed a calibrated limit. The Fuel System Monitor will store the appropriate DTC when a fault is detected as described below.

1. The heated oxygen sensor (HO2S) detects the presence of oxygen in the exhaust and provides the PCM with feedback indicating air/fuel ratio.

2. A correction factor is added to the fuel injector pulsewidth calculation according to the Long and Short Term Fuel Trims as needed to compensate for variations in the fuel system.

3. When deviation in the parameter LAMBSE increases, air/fuel control suffers and emissions increase. When LAMBSE exceeds a calibrated limit and the fuel trim table has clipped, the Fuel System Monitor sets a Diagnostic Trouble Code (DTC) as follows:

The DTCs associated with the monitor detecting a lean shift in fuel system operation are DTCs P0171 and P0174.

The DTCs associated with the monitor detecting a rich shift in fuel system operation are DTCs P0172 and P0175.

4. The MIL is activated after a fault is detected on two consecutive drive cycles.


Powertrain Control Software, Fuel Trim
The fuel control system uses the fuel trim table to compensate for normal variability of the fuel system components caused by wear or aging. During closed loop vehicle operation, if the fuel system appears "biased" lean or rich, the fuel trim table will shift the fuel delivery calculations to remove the bias. The fuel system monitor has two means of adapting Short Term Fuel Trim (FT) and Long Term Fuel Trim (FT). Short Term FT is referred to as LAMBSE and Long Term FT references the fuel trim table.

Short Term Fuel Trim (Short Term FT) (displayed as SHRTFT1 and SHRTFT2 on the scan tool) is a parameter that indicates short-term fuel adjustments. Short Term FT is commonly referred to as LAMBSE. LAMBSE is calculated by the PCM from HO2S inputs and helps maintain a 14.7:1 air/fuel ratio during closed loop operation. This range is displayed in percentage (%). A negative percentage means that the HO2S is indicating RICH and the PCM is attempting to lean the mixture. Ideally, Short Term FT may remain near 0% but can adjust between -25% to +35%.

Long Term Fuel Trim (Long Term FT) (displayed as LONGFT1 and LONGFT2 on the scan tool) is the other parameter that indicates long-term fuel adjustments. Long Term FT is also referred to as Fuel Trim. Long Term FT is calculated by the PCM using information from the Short Term FT to maintain a 14.7:1 air/fuel ratio during closed loop operation. The Fuel Trim strategy is expressed in percentages. The range of authority for Long Term FT is from -35% to +35%. The ideal value is near 0% but variations of ±20% are acceptable. Information gathered at different speed load points are stored in fuel trim cells in the fuel trim tables, which can be used in the fuel calculation.

Short Term FT and Long Term FT work together. If the HO2S indicates the engine is running rich, the PCM will correct the rich condition by moving Short Term FT in the negative range (less fuel to correct for a rich combustion). If after a certain amount of time Short Term FT is still compensating for a rich condition, the PCM "learns" this and moves Long Term FT into the negative range to compensate and allows Short Term FT to return to a value near 0%.

As the fuel control and air metering components age and vary from nominal values, the fuel trim learns corrections while in closed loop fuel control. The corrections are stored in a table that is a function of engine speed and load. The tables reside in Keep Alive Random Access Memory (RAM) and are used to correct fuel delivery during open and closed loop. As changing conditions continue the individual cells are allowed to update for that speed load point. If, during the adaptive process, both Short Term FT and Long Term FT reach their high or low limit and can no longer compensate, the MIL is illuminated and a DTC is stored.

Whenever a fuel injector or fuel pressure regulator is replaced, Keep Alive RAM should be cleared. This is necessary so the PCM does not use the previously learned fuel trim values.

 

Ken:

Very interesting! If I understand this correctly, it would be the opposite of what I was thinking before. A -100% means that the PCM is trying to correct for a rich mixture or as it says, a lean shift. The other scanner I had showed P0171/P0174 defined as "System too lean". The HO2S reads 0.0v which I think is a lean condition! Isn't that contradicting eachother? Or do I have that backwards? I asked AutoXray about HO2S testing and was told that my PCM doesn't support that but they told me how to monitor them in real time, which I haven't tried yet, so I don't know if I'll get a different value.

BTW: It was my handheld PCs background program stealing the Comm port.

 

Ken:

Along with my Too Lean codes I get a rough idle if I let idle five minutes or so. I did a capture this morning waiting for the rough idle. It's going from a Closed Loop to a Open Loop! Don't the HO2S keep it in the Closed Loop? Wonder what I'm losing? Is this another problem or is it connected to the Too Lean condition?

 

Ken:

I went poking around at the forum in http://www.obdii.com and found a posting on a 96 Ranger 4.0L with the exact same backwards reading of -100% trim compared to zero volts on the H02Ss! I emailed the poster and revived the post too!

I got the Enhanced OBD II upgrade for the EZ Link yesterday! Wow, I get 66 parameters now. More confusion

I do have a few issues with the upgrade. It may have a bug or two.

 

Bill,

Thats a good site, can't complain about an upgrade. Let me know how things go, it sounds like you might have one of those tough issues.

Ken

 

[updated:LAST EDITED ON 02-Mar-02 AT 11:10 PM (EST)]Ken:

Real tough problem and I think that if I would have took it in to be fixed, they would have had a problem finding this one.

I found another and posted there too! It's http;//www.eng-tips.com. That's not engines but engineers, lots of high-tech talk but there are posts asking about maintainence problems too.

 

I'm new to the list, and was interested in your post about your time in the Sterling plant.

Maybe you, or somebody on this list could help me identify the rear axle in my '94 Ranger XL 4X4? The door sticker says it's an "R6" axle, and the book at my local Ford dealer doesn't list that one! I got the truck used (up) from my local utility company's fleet, and I'm sure they special-ordered it.

I can tell from the tag it's an 8.8 inch rear with limited slip and 3.73 gears, but I'd like to know what the weight rating is for that axle? 2750#? 3200#? Or something else?

I'm converting the truck into an electric, so I'm thinking about the weight of all those batteries.
Thanks!

 

KenWells:

If the tag states 2750, that's what it is! I just went out and looked at my 97 Ranger, it's a R6 also, rated at 2750 also. I thought that I had the order form the truck but I don't but I remember that it's a limited slip too. At times, Ford might use a complete rear end assembly from somebody else like Dana but they should still be able to find the code in the book.

They also might not build a limited slip in a certain ratio or a certain vehicle. Seeing that I work where I do, it's just a matter of talking to the right people That also holds true if you happen to have a current problem that they are looking for. I(we) can get a whole new rear end without going to the dealer, all while we work too!

 

Thanks for the quick reply!

I'm still confused about the weight rating, because I don't see weight specifically on the tag. Is it coded there? The tag says:
S359B
3L 73 88 4E24

I know that the first part of the second line means it's a locker with a 3.73 ratio, and it's got the 8.8 inch pumpkin. Can you tell any more about it, or are the rest just production sequence numbers?

Thanks again!

 

Yes, the weight per axle should be on the door tag. Or are you refering to the tag on the axle? I could probably get the info for the tag on the axle.

The area where I work is mostly drive shaft and components. Close by is the components and assembly for the F350 series. All the Ranger, F series, Explorer, etc. is at the other end of the plant.

I'm at work now on a wireless handheld PC but depending when you reply, it might have to be Monday before I can find anything out for you.

 

It's great if you can look into it for me!

Yes, the numbers are from the axle tag.

Thanks
-KenW