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4.0 OHV speed limiter delete

thcscubajohn

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Does anyone know how to remove the speed limiter on a 94 4.0 OHV I believe it is a fuel cutoff but I'm not sure if it is in the pcm or somewhere else

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farmer

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No speed limiter on a 94, just usually lack of power. Had my 94 fast enough the needle was pointed at D on the gear indicator.
 

RonD

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The EEC-IV computer(1994 and older Rangers) will have a REV limiter, and I think some Mustang EEC-IVs did have speed limiters not sure on Ranger EEC-IVs, but if it does have one I would guess 90MPH would be top speed

The 1995 and up EEC-V computer did have both

EEC-IV needs a "man in the middle" circuit board to make changes, it isn't programmable like the EEC-V
But if speed is the only issue then you can adjust the speed the computer sees :)
By changing the signal from from the VSS(vehicle speed sensor) signal on the speedo cable hook up, speedometer on dash would remain the same/correct because it uses the cable, the VSS signal was only used by computer and cruise in 1994.

Or you may just be able to unplug the VSS from speedo cable on trans, so computer has no speed reference, not sure on that.

Or if you are not worry about correct speed on speedometer then just change the gear on the speedo cable to show lower speed than actual speed.


I wouldn't drive my 1994 above 80MPH on any road, lol
 
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chewy012

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^ It not in common for me to bury my needle at 85 with tires 1 size over stock and it's a '92 with 243k+ [emoji14] runs like a bat outta hell some days. 98% of days I drive 'er easy, but sometimes.... ;)

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thcscubajohn

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The truck will limit to 4000 rpm in 4th and ~3000 rpm in overdrive (5th) it will shut off the fuel and I'm wondering where that program is and I didn't know that the truck could tell what gear the manual transmission was in as for the speed I'm not quite sure the needle goes past 85 probably past 90 too but the needle stops at the dash it hits it and stops but the speed will still increase and if I'm going down a hill I can get overdrive to go to ~3600 rpm before it kicks in then the fuel shuts off till it gets down to 2700 then I can go back up to 3100 and it will kick in again

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adsm08

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Any speed limiter will be in the PCM. But it can't tell what gear you are in, so your theory that it cuts off fuel at different RPMs for different gears is wrong.

You are probably running out of power, or have a weak fuel pump that can't keep up.
 

thcscubajohn

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I will post a video showing that once the rpm reach these rpm ALL engine power will cutoff and it will be as if I let off the gas completely I am certain that there is not an issue with power

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firehawk618

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Any speed limiter will be in the PCM. But it can't tell what gear you are in, so your theory that it cuts off fuel at different RPMs for different gears is wrong..
Actually your theory that since there's no gear input to the PCM = it couldn't limit rpm vs gear is wrong.

I am NOT saying that this is the case with these PCM's but I know in others the computer calculates gear based off of RPM + VSS input to it and adjusts things accordingly.

Again, I am NOT saying the EECIV in these rigs does that but I am saying that just because there is no gear sensor input to the computer does not rule out that it could limit RPM vs speed based on the gear it calculates it is in.
 

adsm08

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Actually your theory that since there's no gear input to the PCM = it couldn't limit rpm vs gear is wrong.

I am NOT saying that this is the case with these PCM's but I know in others the computer calculates gear based off of RPM + VSS input to it and adjusts things accordingly.

Again, I am NOT saying the EECIV in these rigs does that but I am saying that just because there is no gear sensor input to the computer does not rule out that it could limit RPM vs speed based on the gear it calculates it is in.
You are correct, if the vehicle is equipped with and input shaft and output shaft speed sensor, and the computer has tables to tell it what each gear ratio should be it can calculate the gear ratio. In a manual trans setup the crank sensor can be substituted for an input shaft sensor, since they are mechanically connected. However there isn't a true output shaft sensor on these transmissions, and the computer doesn't have the needed software to do the calculation.

So since you insist on splitting hairs like this: HIS TRUCK HAS NO WAY TO DETERMINE WHICH GEAR A MANUAL TRANSMISSION IS IN.
 

RonD

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If you look here: http://www.auto-diagnostics.info/ford_eec_iv

Pin 30 on the computer is used as a "neutral switch", 0volts at pin 30 would enable REV Limiter, so a broken wire for pin 30 could be your problem.
If pin 30 has 5volts then no REV limiter

Pin 26 is computers internal voltage regulator, 12v to 5v, this 5 volts is used to power sensors.
 

firehawk618

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So since you insist on splitting hairs like this: HIS TRUCK HAS NO WAY TO DETERMINE WHICH GEAR A MANUAL TRANSMISSION IS IN.
Since we're now splitting hairs......

The PCM would only need to know the RPMs of the engine and the vehicle speed to calculate the gear it's in whether it's a manual or an auto.

In fact I recently had a car that calculated the gear in this exact manner. We used the desired torque vs gear vs rpm tables in the stock PCM all the time and rest assured, this car has no sensors on the manual transmission either.

I've been looking for a while for a .bin dump of any EECIV that came in the Rangers/Bronco II's and have found none so far. I'm very curious as to exactly what tables are in these computers.

So if you are saying the EECIV has no tables for this then touche.

If you are saying the EECIV can't do this due to no input / output shaft sensors then you are mistaken.


Just wanting to put good facts out there.
 
Last edited:

thcscubajohn

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Smog is for pussies.
I never assumed that the pcm knew what gear the trans. was in but as you can see in the video it cuts out at exactly 3000rpm in O/D and 4000rpm in 4th. Can the speedometer cable limit the speed because if I am going down a hill I can get it to 3000 in O/D and 4400 in 4th the truck will accelerate then suddenly loose all power as if I turned the ignition to the office pos. with it in gear but all the lights stayed on because the engine is turning and the ignition is in the run pos. if I'm going down a hill it will lag to cut off [fuel I believe but maybe air] I would just like to get rid of this to see how fast I can honestly at 4750 rpm in O/D


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tcbaklash

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115mph on flat ground is probably all you're going to get. I don't mean to sound like a party pooper, but I don't think that it would be worth the effort to defeat the limiter for a vehicle that can't achieve Autobahn speeds, let alone accurately display any velocity above 85mph.
 
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AllanD

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I run a 1993 4.0 engine and PCM in my personal truck and I can assure you that it will do more than 115mph on flat ground.

I have a Gen1 truck with the 140mph motorsport speedometer and I've had it to 125-ish several times, I say "-ish" because at that speed in the wind conditions I didn't take the time to "Study" the speedo.

I'm sure the truck would go faster than 125mph because each time I have attempted a speed run I've managed to lose a balance weight off a front wheel which caused me to abort the run at just over 125.

When this truck was built it had a 2.9 in it and I know I could get into the factory speed limiter (112mph) with that engine and a slight tailwind... and the 4.0 though not as revvy, is a much better torque producer across the entire rpm range...
 

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