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Change your MLPS / neutral safety switch.. now!

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  #1  
Old 06-04-2011, 11:48 PM
ErrorS ErrorS is offline
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Change your MLPS / neutral safety switch.. now!

So, my occasional (VERY occasional) code for a neutral safety switch? I thought, "so what, I sometimes have to push up into park to get it started, not vital, it can wait". You know, the neutral safety switch on my C6 in my F150 and other Bronco doesn't do a whole lot, so why bother.

Well, my tranny has been acting weird, did some searches on the subject and everything led to the MLPS, Transmission Range sensor or what Autozone and my codes call it, a neutral safety switch. Saw CM throw the code again, so I went ahead and changed it.

I now have a whole new Bronco. Everything from my idle in park, to shifting to engine power to.. well, just about everything in the Bronco is working better.

I thought I had replaced or fixed everything in the finicky speed density sensor chain and was just fighting a tired, worn engine, no power, rough idles, you know the deal.. not thinking a neutral safety switch was part of this chain and thinking it was something totally different than the MLPS I kept hearing about. Sure enough, signal return to TPS among other things.

So, if anyone hasn't done it yet with a 94' or earlier, DO IT NOW. Trust me! it helps in areas you don't expect and doesn't seem to throw codes very often, if at all. No joke when I say I feel like I just gained 100 horsepower and upped my mileage at the same time.

and I had no clue this Bronco could idle at 550RPMs and sound so smooth..

edit: Oh yeah, one more thing.. my loud CLUNK is gone when shifting from park to reverse and vice versa. Apparently my engine was reving high in between shifts and causing it, the MLPS change stopped it completely.
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Old 06-05-2011, 12:01 AM
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Edgethis Edgethis is offline
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Sweet!! If only I had a 94 or older. Dang Guess my E4OD really is Funked.
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Old 06-05-2011, 12:28 AM
ErrorS ErrorS is offline
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Your MLPS can still go bad. I didn't have any excessive corrosion or anything, just a bad sensor. The TSB is just because us pre-94s lost them quickly and often because of a bad plug design, it doesn't make your 95 unbreakable :P

try it anyways, seriously, you never know.

oh, and I think I messed up my tranny in the process. For the first time in my life, I understand what burnt fluid looks like
it's driving great, but those 200 miles with a near shot MLPS and really took its toll on my tranny.
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Old 06-05-2011, 10:17 AM
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The REASON for this is simple. All resistive electrical components (which is to say MOST of the sensors in our vehicles) change resistance value as they are exposed to temperature and humidity extremes. Eventually, that resistance value changes enough to affect the voltages that the computer is programmed to "look for". When that happens, the computer compensates whether its really necessary or not. The result is a loss of performance. This isn't to say you should change all the sensors with each tune up! It just means that if the vehicle you are driving is more than 10 years old and still has most of the original sensors, you should consider replacement sooner rather than later and don't hesitate if you are seeing recurring fault codes as this is indicative of a sensor that has reached a "marginal" functionality and is probably doing more harm than good for your performance and mileage.

MLPS - uses resistors of different values to alter the voltage that the computer sees from it. The various voltages that come back to the computer "tell" it what gear has been selected. Each gear has a given resistor that sends a specific voltage back to the computer.

EVP - is a varistor. (Variable Resistor) that changes voltage as the EGR valve opens and closes. Again the change "tells" the computer the position of the EGR valve.

TPS - is a potentiometer (another type of variable resistance device). Varying voltage from it "tell"s the computer how far open the throttle plates are.

ECT and ACT are Thermistors (Thermal reactive resistors). These two change resistance value as they warm up and cool down. They "tell" the computer engine coolant temperature and temperature of the air coming into the intake.

The one thing to ALWAYS remember as well is the fact that ALL but TWO of the sensors in our trucks MUST be fed VREF (the +5VDC power from the computer). If this reference voltage is interrupted, the computer will see it as a problem with that sensor. If this voltage is lower than about +4.75 VDC as it comes TO each sensor, this throws all of the readings coming FROM each sensor off.
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Old 06-08-2011, 10:44 AM
b4hntn b4hntn is offline
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Excellent summary GS. Of course the HEGO needs considerations also.
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Old 06-08-2011, 03:15 PM
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Yes, it does and for much the same reason. Additionally, the older and dirtier the O2 sensor gets, the less reactive it is to the oxygen levels in the exhaust. When the reactivity slows, so does the electricity that is generated as a result of the reaction. That changes what the computer gets from it which equates to a loss in performance.
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Old 06-08-2011, 03:55 PM
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i need a whole new exhaust for my 96, anyone think ford racing shorties, 3" single exhaust no cats with a super 10 is alright? ill still probe the o2 sensors in if necessary. 96 bronco with the 5.8
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Old 06-08-2011, 04:03 PM
ErrorS ErrorS is offline
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I went with 2.5" and wish I had gone with bigger. I don't see why you want to go with a cat delete though, the high flow magnaflow single i got is outstanding.
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Old 06-08-2011, 04:08 PM
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Oh and I don't think there is single county in the US that won't impound your vehicle with a cat delete if you drive passed a cop that's in a bad mood, or some super enviro freak cop.

In a my town in indiana I had an officer look under my bronco for a cat once.
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Old 06-08-2011, 04:13 PM
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where at in indiana? i live in laporte, we have no emissions laws, or testing. i drive by cops with open headers all the time :-) and wave haha and im well known for bad driving (good driving the way i see it) the only time i drive through town is when i go to work, which is at 3 am, and im not all about waking the neighborhood up at that time, i dont wanna be up so why would anyone else? haha. plus my stock exhaust is very horrible. some jack*** decided to cut the muffler off, and somehow cut the pipe so close to the cat that any welding would melt the 02 sensor nuthead to the exhaust, so either way it needs replaced. id put a high flow cat on it, but thats just more money.
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Old 06-08-2011, 06:34 PM
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Well, I'm in terre haute. Even though they don't test, I would bet there are laws. Usually, its one of those laws where they don't enforce it, but if you run into the wrong officer or local politics change they will start busting you.

In my 90 i only have one o2 sensor, before the first cat. The magnaflow cat and h pipe were only 200 together, but it has a single 2.25" outlet which is annoying.
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Old 06-09-2011, 04:45 PM
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not tryin to be rude errors but im not all too worried about getting busted but thanks for the thought :-) i wanted to have my super 10 have dual exit with 45 degrees each side, probably some 3 or 4" tips
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Old 06-10-2011, 12:39 AM
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A failed cat can legally be removed. The fed dropped the mandate on replacement on anything older than 1995. And no cop can impound your ride for a missing catalytic converter. If your registration is current and your vehicle must undergo a safety and emissions inspection to get it, they have no legal grounds to impound the vehicle. The obnoxious state of California might try a stunt like that but the cop would need "probable cause" to stop the vehicle before any inspection could be done. So, since no cop can observe a missing cat as you drive by, it's not gonna happen.

Now, let's give Errors his thread about MLPS replacement back.
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Old 06-10-2011, 12:57 PM
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I think I am going to try this. Ive been through everything in my truck, it starts runs and drives fine. But, it does have the issue where i need to push up on the shifter to get it to start sometimes, it does have the park to reverse slam that I hate, and it just doesnt seem like it has the get up and go it should. I am getting 11/14 ish for mileage which aint bad from what I am told. I think I will gamble the cost of the sensor for the possibility that i get some driveabilty improvements. My truck is a 93, I have 109k and I am reasonably sure it has the orig sensor. I think this will be my next repair.
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Old 06-10-2011, 03:14 PM
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Quote:
Originally Posted by greystreak92 View Post
A failed cat can legally be removed. The fed dropped the mandate on replacement on anything older than 1995. And no cop can impound your ride for a missing catalytic converter. If your registration is current and your vehicle must undergo a safety and emissions inspection to get it, they have no legal grounds to impound the vehicle. The obnoxious state of California might try a stunt like that but the cop would need "probable cause" to stop the vehicle before any inspection could be done. So, since no cop can observe a missing cat as you drive by, it's not gonna happen.

Now, let's give Errors his thread about MLPS replacement back.
It's okay, I find this interesting. When did the feds do this because this was last year that a cop told me. I would have skipped my cat if I had known but every single exhaust shop here told me that they couldn't touch my exhaust for ANYTHING if it didn't have a cat.

and mike, you didn't do anything to offend me, I just dealt iwth this recently so it's an interesting subject for me.
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