Thought I'd better start a new thread, as the last one (fuel gauge not working) was getting too long.

My truck's still not registered (tires too big and I have to find a bench seat somewhere to replace my bucket seats). Meanwhile I'm still sorting out my engine. Finally got my hands on a code reader and ran a KOER test. I got several codes, two of which concern me here: code 25 (knock not sensed during dynamic response test), and code 41 (O2 sensor voltage low/system lean).

Code 25
My workshop manual says that only trucks with automatic gearboxes have sensors, so I don't get this. There was a sensor of some kind lying loose in the valley of the lower inlet manifold (white, with a black tapered inner cylinder) that clearly was meant to plug into another connector, with two wires (black/white and green) going into the wiring loom, and as it didn't seem to be doing anything I just cut the wires and taped them up. Was this the knock sensor, and should I reconnect it?

code 41
Warmed the engine up, then checked the voltage delivered from the sensor, which was steady at around 0.58 volts. Blipped the accelerator and it flipped up to around 0.73 volts, so wouldn't that mean that the sensor is functioning correctly and indicating a rich air fuel mixture? Only problem there of course is that the computer says the opposite (system lean).

My O2 sensor is the single wire type, so I first checked the ground from sensor body to battery negative: resistance was two ohms. Then I checked continuity from sensor to the computer plug terminal...again two ohms. So the computer is getting a system rich signal from the O2 sensor and interpreting it as a system lean condition. The computer is at least thirty years old, the fuel pumps run continuously (symptomatic of leaking capacitors in the computer), so would it be the computer?

Also, the engine surges very slightly on idle with the 02 sensor connected, but runs perfectly when it is disconnected.

As always, any help greatly appreciated, fellas.

 

Knock sensor is part of your engine wiring. It has a lightgreen/black dot wire and a black/white stripe wire.

Here is a picture of the location.

 

As for the computer, I seem to recall a thread on here about fixing the leaking cap on the board. I'm sure if you ask google, how to... you could find that fix.

Do you need me to get a good picture on my knock sensor ?

 

Hi, Dave. Thanks for the diagrams, and yes, on closer inspection the green wire from my component does have black dots; so I reckon it is the knock sensor all right. There's just no where on the engine where it could be plugged into something...it's always just been lying there. Would there be any point to rewiring it into the loom, if it's not actually hooked up to the engine?

 

Hi Max. I certainly would like to see how and where it plugs into the engine, if you happen to have a photo handy.

The computer is about 32 years old, and the 02 sensor would be original, so it's pushing 40 years old. The computer obviously needs repair or replacement, as it is misinterpreting a clear system rich signal from the O2 sensor, but what about the sensor itself...do I actually have a system rich condition, or is the sensor faulty as well?

 

Actually fellas, I've got two more questions.

First question: my tires (37 inch by 12.50 inch Coopers STT) still have good tread, but it's old rubber, maybe fifteen years...so too old?

Second question: my rims are 17 inch by 12.50 inch, and I have to dig up some much smaller 31 inch tyres from a junk yard to pass inspection, but tires that small are typically made to fit on a narrower rim, like 10.50 inch wide say...so how would you go getting them to mount onto a two inch wider rim? Could you do it if you used inner tubes and extra air pressure to spread the side walls? I'd be putting my Coopers back on straight after I pass inspection.

 

I say save yourself money and time and just get new tires and wheels.
Tires no matter how good the tread is they are only good for about 5 to 7 years max. Look them over really good for dry rot / cracks in the sidewalls and tread.

I just bought a car with 22000 miles with tires that were 11 years old that looked good till you looked closely and had cracks in the tread.
Even the shop I took it to for new tires came out and said they looked good and why I was changing them till I told him of the year and cracks.

There has to be a reason why it will not pass with the large tires and you want to put them back on?
A 31x10.5 tire will fit a 10" wide wheel but they dont last long so they should be on a 8" wide wheel.
Can you even get tires for a 17" wheel and why I said wheels & tires.

I dont know but in my old age I like to be a little safer for me and others.
Dave ----

 

Found them, "knock sensor" that's it down there behind that black plastic tube that goes into the ait filter box. I'd say its between #6 and #7 injectors.

 

I agree with Fuzz, just round you up some stock steel 8 lug rims and put the smaller tires on them. That is assuming your smaller tires are 16 inch.

 

What you say is of course totally good sense as usual, Dave and Fuzzy.

I shouldn't even have asked the question about the age of the tires as I have experienced the result of driving on faulty tires. My truck was only six years old when I got her, and I never questioned the tires, which were 31 inch with plenty of tread. Thinking back now, they must have been retreads, because one front tire threw a tread when I was tootling down the freeway at 120 kph with a ton of firewood on the back. Turned the tread basically into a whip belting around in the wheel arch. Not an experience you forget easily...

So yes, I'll prise open my wallet yet again and fork out the ready for a new set...but I have to admit I'm wedded to big tires. Less efficient braking and not so stable, I know, and geared up which means less acceleration; but on the upside you've got better traction and clearance over the rocks, more resilience to impact (Can you believe some idiots put low profile tires on their trucks just for appearance?), and the higher gearing helps fuel economy, which is kinda useful over here with long distances between watering holes.

Maybe though I'll drop down to 35 inch to lessen the strain on my steering gear.

 

Thanks for the photo, Max. That's where I thought it would go, but there's nothing there...no plug in mount, nothing. Our Aussie built Windsors must be different, I guess. So maybe not bother reconnecting the sensor to the wiring and computer input?

 

Also, what do you think I should do about the O2 sensor? Going on the readings I took above, would you say it's okay...or should I replace it?

 

There should be some kind of port/hole in the lower intake manifold where the sensor would screw/ mount into. Playing around today, I got the 4ft stepladder out and decided to try and get a better picture.

I see it threads in, I searched for it,
https://www.google.com/search?q=1986+Ford+302+EFI+knock+sensor&sca_esv=6e ed89d831f7228a&sxsrf=AE3TifOIbId7OpXDADK4cVbwTyLWt PDT7Q%3A1763225438280&source=hp&ei=Xq8YaeWCD8aqw8c PoZ_QkAk&iflsig=AOw8s4IAAAAAaRi9burV3_hN0p9coTXTiC 568Qryl5RU&ved=0ahUKEwjlqZ_PzvSQAxVG1fACHaEPFJIQ4d UDCBo&uact=5&oq=1986+Ford+302+EFI+knock+sensor&gs_ lp=Egdnd3Mtd2l6Ih4xOTg2IEZvcmQgMzAyIEVGSSBrbm9jayB zZW5zb3IyBRAhGKABMgUQIRigATIFECEYoAEyBRAhGKABMgUQI RirAkj0gAFQ4Q9YhnZwAXgAkAEAmAHcAaAB4hSqAQYyNi4zLjG 4AQPIAQD4AQGYAh-gAswWqAIKwgIHECMYJxjqAsICDRAuGMcBGCcY6gIYrwHCAgoQI xjwBRgnGOoCwgIHECMY8AUYJ8ICBBAjGCfCAgoQIxiABBgnGIo FwgILEAAYgAQYsQMYgwHCAggQLhiABBixA8ICBRAAGIAEwgILE C4YgAQY0QMYxwHCAggQABiABBixA8ICCxAuGIAEGLEDGNQCwgI LEC4YgAQYxwEYrwHCAgsQLhiABBixAxiDAcICBRAuGIAEwgIEE AAYA8ICBhAAGBYYHsICCxAAGIAEGIYDGIoFwgIIEAAYgAQYogS YAw7xBQPIWlidSMVWkgcGMjIuOC4xoAeczQGyBwYyMS44LjG4B 74WwgcJMC4xMS4xNi40yAeZAQ&sclient=gws-wiz

 

My truck had 35's with a 4 inch lift when I got it. It does give a commanding look to it. I disagree with the fuel mileage thing though. Why don't you check the mileage with the small tires, and then with the larger tires. I bet you lose 1-2 mpg with the larger tires. Of course it throws your speedo off, so you might have to use some sort of phone app to figure your distance.

My truck was a diesel with 4.10's. The best stock setup you could possibly use with oversize tires besides a 460. If you have a 302 with 3.55's gears or less, those 37' have to absolutely kill your power. My diesel doesn't have much power either, and I finally went back down to a 31 inch tire. The pulling power increase was dramatic, and now I can get the truck in my garage with the 7ft door(barely but it fits). And using the bed and getting in and out is much easier also.

But I have to admit, it doesn't look as good as it did with the 35's on it.

 

Hope you don't mind, I started a thread over here, https://www.garysgaragemahal.com/

Asking about your knock sensor...maybe one of the experts over there can help...

If you have the sensor, you should reconnect it and put it back where it was.