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Changing speedometer conversion constant in the EEC-IV- possible at-home?
According to the '92 Ford Owner's Guide, the "conversion constant" in the EEC-IV "can only be changed three times once the vehicle leaves the factory" (pg. 59). My F250 came with some wheels and tires that I'm not sure I'm going to keep, and the OD on the tire is 31.7" (nominal for LT235/70R17's).
(I just got back from Portland, Oregon, and haven't had a chance to wash it yet.)
I'm not sure what I'm going to do yet with regards to these wheels & tires, but my immediate question is: Is this "conversion" in the EEC-IV is something I can do?
There are several videos about the procedure to adjust your speedometer for different tire height. 3 times only is only half what I thought. I've done my 95 twice and it has 3 times left. If your 92 only has 3 maybe no one has ever adjusted it and you can be the only one who gets to.
There are several videos about the procedure to adjust your speedometer for different tire height. 3 times only is only half what I thought. I've done my 95 twice and it has 3 times left. If your 92 only has 3 maybe no one has ever adjusted it and you can be the only one who gets to.
I assume I can find these videos on Youtube (I haven't looked yet), but either way, good to know I can do this!
There are several videos about the procedure to adjust your speedometer for different tire height. 3 times only is only half what I thought. I've done my 95 twice and it has 3 times left. If your 92 only has 3 maybe no one has ever adjusted it and you can be the only one who gets to.
You just need a set of alligator clips to ground the PSOM under the passenger side of the dash. Watch a couple of YouTube videos before doing it but keep in mind that actual rotations per mile and manufacturer advertised rotations per mile for ANY set of tires at a given air pressure are not going to match. I went from a 34.5" tire to a 33.1" tire and used Goodyear's rotations per mile number for my calculation and my speedometer ended up 5mph off at 60mph via GPS it was reading 65mph on my speedo.
How far is the speedo off? I would consider that before wasting much time thinking about it.
(LOL!) I'm ashamed to admit I don't know yet! I haven't had it that long, and I prefer the mileage in my F150 so I haven't driven it all that much, but I just took it on a 1,700 mile trip, but didn't think to check the odometer against the mile markers (I'm Old School) until I was about 5-6 miles from home.
But I have another, shorter trip coming up in a couple weeks, so I'll check it then.
Just nice to know I can make a change once I figure out what I'm going to with these tires & wheels (too "new", and don't really go with the truck, in my opinion).
You just need a set of alligator clips to ground the PSOM under the passenger side of the dash. Watch a couple of YouTube videos before doing it but keep in mind that actual rotations per mile and manufacturer advertised rotations per mile for ANY set of tires at a given air pressure are not going to match. I went from a 34.5" tire to a 33.1" tire and used Goodyear's rotations per mile number for my calculation and my speedometer ended up 5mph off at 60mph via GPS it was reading 65mph on my speedo.
Thank you! I'll do some digging around on Youtube this week and see what this entails.
And who knows? Maybe it's "good enough" as it is right now, I don't know. But I have my doubts, as these tires "look" shorter than other F250 tires I've been looking at while driving around.
My F250 came with some wheels and tires that I'm not sure I'm going to keep, and the OD on the tire is 31.7" (nominal for LT235/70R17’s)
Not as nice as the factory Alcoas but they aren’t terrible. How does that size combination compare to what is listed on the B pillar?
Originally Posted by Jim_K
But I have another, shorter trip coming up in a couple weeks, so I'll check it then.
Just nice to know I can make a change once I figure out what I'm going to with these tires & wheels (too "new", and don't really go with the truck, in my opinion).
I certainly would not waste a calibration change for something you might not keep. I would see how far it is off and keep that in mind when driving. That’s what I did when I put 35’s on the Bronco.
I am not sure that 92 has a PSOM
But if it does, it sure is easy to change (or find out if you are out of changes)
It was 3 times IIRR
Rule of thumb is 5 seconds at 60 mph
If you are off less than that, a driven gear change or PSOM adjustment is not needed as you will be off the other way
rip steve, wish I knew what he did to get banned here lol... I left the other ford truck forum because hes knowledgeable yes but hes quite the blowhard.
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