Well, for some reason my '94 F150 with a 300 runs OK all around, except for at 30MPH cruising while vacuum is at 9.5-11hg/inch and while cruising at 50MPH and faster.

At the 30MPH it starts hiccuping and losing power and the only way to get it to stop is to let off the gas until vacuum is over 9.5-11hg/inch or sharply depress the gas pedal and keep it there until above 30MPH

at 55MPH and faster my air/fuel ratio gauge starts pegging lean instead of fluctuating back and forth, and it does not move, it just sits there, if I play with it I can back off the gas pedal enough to get it to instead be in the ideal middle range or in the rich range, however it slows the truck down slowly until it's going about 45MPH.
If I do 100% throttle it will go to rich, which I expect it is suppose-to do, but aside from that any other acceleration/maintaining speed results in Lean.

Normally, I'd say "Gee, I bet I was a complete moron and it's not hooked up right" but the computer keeps throwing codes 173(HEGO sensor fault/rich) and 179(HEGO sensorfault unable to switch / rich during part throttle), I'm also getting 628(Excessive converter clutch slippage) now

 

How old are the plugs, wires, cap and rotor? Same for the filters? How old is the O2 sensor?

A missing cylinder will dump unburned fuel into the exhaust. The PCM reads this as a rich condition then it starts pulling out fuel which leads to an actual lean condition.

 

doe's the truck have cats on it , if so see if there clogged , with that vacuum reading ?? the cheap A/F gauges are not very acurate...Lew

 

Good point Lew!

 

is it changing gears like it should cuz it almost sounds like the computer is telling it to change gears adjusting the the/air fuel ratio like it did but its rele not causing you to have a lean condition "628(Excessive converter clutch slippage)" is my reasoning behind this it could be having problems with changing the gears and that would mess with ur A/F ratio if the computer thinks the tranny has changed gears when it real isnt

 

The cats were replaced in February of this year with a walker three-way cat, O2 sensor was replaced in March I believe because of codes 173/179, it is a bosch sensor

Plugs are about a year or two old, they are all white and gapped to .55 for the Sixlitre upgrade
Wires are about three to four years old and are blue 8mm accel wires
Cap and rotor were replaced in January too while trying to fix an issue where it was extremely hard to start and would stall if gas was not given, turned out to be the EGR system and was fixed; same reason cat and mufflers were replaced

Tried another MAP sensor and no change, TPS was replaced under warranty in January too for the same reason as the cap and rotor.

The tranny seems to be hesitant to go into the next gear while doing 30MPH, also have heard/noticed "Shifts" while cruising 50MPH or faster but only by sound and feel, by the time I look at the tachometer it's too late.
These are not the first tranny codes I've gotten either but I don't remember the others right off hand, one was that the MLPS for my E4OD was bad/needed adjusting but they come and go

 

A very lean mixture can burn up a converter in a hurry. I have seen some screwy things happen with the O2 sensor signal when the chassis/body ground is not 100%. It may sound like a broken record but go through all the grounds to verify they are clean and tight.

More than once the ground to the radiator support, G100, or the body ground, G101, have turned out to be less than stellar and cause weird symptoms. G104 is the ground for the PCM itself. It is located on the rear of the left hand fender apron. That is another good one to check.

 

The problem is still there though after fixing I think it's G101 by the battery, but it DOES however vanish while the engine is cold, but as soon as it's warm(About as much that takes to hit 55MPH from a cold start and getting going) it goes lean.

Also, I'm getting the occasional late shift now and an occasional shutter again while accelerating; Which I had from the tranny being overfull but that problem has been resolved and the dipstick says it's in the proper range.

Tranny is an E4OD, truck has nearly 200,000 miles on it now, it does NOT have the updated connector/solenoid.

Does anyone have diagrams by any chance of the other grounds? I tried finding them in my haynes but I haven't really been successful.

 

Here are some drawings from subford:

 

My grounds look good, today I finally got around to probing my TPS and it sits at 4.9v instead of changing from .50-5v at idle, and I've tried with two different sensors, any ideas?

 

The Six litre tune up is intended for the V8s... you should re-check your timing and reduce the gapping, i would check fuel pressure, regulator and filter also.

 

Which wires are you probing on the TPS?

 

The top and bottom wires, I forgot what they're called but it's how the Haynes says to do it, if polarity is switched on the ends it doesn't come back with a reading( 0.00), my TPS has 3 wires in a oval shape connector.

I replaced my FPR, which solved with an occasional stalling condition, fuel pressure reads good while parked but my gauge doesn't have enough hose to run it up enough to tape it to the windshield while I drive; The filter was also changed about 4 times in the period of 3 years or so, just for preventative maintenance(First change, filter was full of sludge, second and third just to make sure it was all gone, by third there wasn't any more left)

I also asked on FSB where I followed the guide and they posted back that it should all be fine/the same since it's basically just increasing the timing/plug gap from the same gap and timing.

 

You are measuring the VREF and Signal return. You need to measure the TPS output signal and return. Use this from Ford Fuel Injection as a reference: Ford Fuel Injection Throttle Position Sensor (TPS)

 

How does one probe the sensor properly?
Insert the voltmeter probes next to the wire in the rubber of the pigtail?

Meant to be done running or only while KOEO?