Gas pedal sensor woes

Master M

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I just got more validation not to buy a newer car if at all possible.
A casual friend told me today they got stuck 100 miles from home because their 2010 car would not accelerate over 30 miles an hour. They had to limp 80 of the miles to get to a mechanic. I start thinking what could be the problem. A few things that came to mind were the typical fuel filter clogging, weak fuel pump, etc. They stopped by and told me later it was the gas pedal sensor. I stopped and said WHAT!!! your car has a sensor to monitor the gas pedal, how ingenious. All of my gas pedals are decades old and work great and I have never inspected them. So don't forget to check your oil and have your gas pedal sensor inspected before that road trip !!! How about checking all of the sensors before that road trip, there are only 12 to 30 in the average car. Below is from yourmechanic.com

Within the electronic throttle control system in your vehicle is an accelerator pedal position (APP) sensor. It's one of the many sensors in your car, and like the others, this one is responsible for an important job. What this sensor does is aid in the process of converting the pedal movement to a voltage signal. In a nutshell it's passing on a signal in relation to the position of the throttle. The signals are sent on to the ECM, which is the electronic control module. This information is vital in the vehicle’s combustion process.

This part can fail over time because of the high level of heat it is exposed to on a regular basis. Other factors that play into its' failing are dirt and debris, moisture building, a large amount of pressure, and more. This is not a part that can be repaired, so when it fails it needs to be replaced. A good rule of thumb is to have it inspected from time to time, so you don’t run the risk of it suddenly failing.
 

Cordoba1

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Eh.... Chrysler has been using them since 1975 on the Lean Burn systems. I'm actually a fan of lean burn. The prevailing logic has always been to rip it off when it stops working, but many issues can be diagnosed back to a failing sensor. Lean Burn uses a TPS to determine rate of throttle change. For example, by using both the TPS and the vacuum sensor; if the computer detects a fast WOT condition, it will start the acceleration timing advance program. By the way.. I love my old car, and I love my new car, too. I drive the old one locally; but if I have to drive a few hundred miles in a day, new car trumps old car.
 

Aspen500

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He is talking about drive by wire where there's no throttle cable. The pedal has 3 sensors, two that have inverse signals (one goes up, the other down) and a third as a "back up" and to justify the signals from the other two. They send a signal back to the ECM which in turn send the command to the throttle body to open the throttle plate a certain amount. The TP sensors send back a signal to the ECM for throttle position. There are all sorts of fail safes built in to the system. In the event of a fault it'll go into "limp" mode or "reduced power mode". Could be a fault in the ETB system OR with the engine or trans that might result in severe damage that puts in limp mode. Of it was a momentary fault, usually shutting the car off and restarting will take it out of limp mode, provided the fault is no longer present.
That said, in the roughly 20 years since drive by wire on gas engines came around, I've seen VERY FEW failures. It's actually a really reliable system. Diesels have had drive by wire for even longer, Ford started it in 1992 (I think it was) on the 7.3L diesels for example.
Drive by wire adds things that could fail at some point but eliminates others like the idle air control solenoid and cruise control servo and the idle can be more precisely controlled.
 

Justwondering

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As I raise my hand to ask a question...(novice)
TPS -- throttle plate sensor
WOT -- ???
ECM -- Electronic something something

I'm looking through the service manual but it has no index so these are under engine or fuel or carb subsections?

Need to get some sticky notes and stick in this book.
 

AJ/FormS

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TPS is Throttle Position Sensor
WOT is Wide Open Throttle
ECM is Electronic Control Module
MAP is Manifold Air Pressure
MAF is Mass Air Flow
CTS is coolant Temperature Sensor
NASA is LIARS one and all.
Evolution is a theory
There's only two ways to prove the earth is a ball, from earth;1) to fly over the the Southern "continent" from one ocean to the other, and 2) to measure the distancesbetween any three southern most land masses, and compare them to a globe based model.
The Antarctic is closed to the public. The land mass distances are impossibly large to measure,and airplanes don't fly direct.
Now, if you had some spare change you could rent a steamer, and set sail.....
There is a third option; you could try to sail all around that ice heap.You might not survive the armies of the world shooting you out of the water tho...
Hmmmmmmmmmmmmmmmmm, what's the big secret?
 
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Justwondering

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So the throttle position sensor (TPS) has a direct line connection back to the computer (brains - ECM?) as well as there is a vacuum line connection. Both these 'connections' work with the Lean Burn to determine how rich or how lean to burn.
Is that right?
 

Mr C

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Here's a pic of the Lean Burn (LB) circuit. You can see the throttle position transducer and vacuum transducer in the pic.

0900c15280087a7a.gif
 

Aspen500

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Mopar had the right idea starting in the 1970's with the Lean Burn and Electronic Spark Control but at that time the computer technology wasn't there to make it work really well yet. I don't mean that it didn't work, just that it could have worked a whole lot better with more and faster computing power.
 

Master M

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He is talking about drive by wire where there's no throttle cable. The pedal has 3 sensors, two that have inverse signals (one goes up, the other down) and a third as a "back up" and to justify the signals from the other two. They send a signal back to the ECM which in turn send the command to the throttle body to open the throttle plate a certain amount. The TP sensors send back a signal to the ECM for throttle position. There are all sorts of fail safes built in to the system. In the event of a fault it'll go into "limp" mode or "reduced power mode". Could be a fault in the ETB system OR with the engine or trans that might result in severe damage that puts in limp mode. Of it was a momentary fault, usually shutting the car off and restarting will take it out of limp mode, provided the fault is no longer present.
That said, in the roughly 20 years since drive by wire on gas engines came around, I've seen VERY FEW failures. It's actually a really reliable system. Diesels have had drive by wire for even longer, Ford started it in 1992 (I think it was) on the 7.3L diesels for example.
Drive by wire adds things that could fail at some point but eliminates others like the idle air control solenoid and cruise control servo and the idle can be more precisely controlled.
That is exactly what I was referring to. Thank you for the details.
 

Cordoba1

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The Lean Burn system does not effect the mixture, but it does control the timing. It uses all of these inputs to determine when to fire the plugs. It does this by following certain schedules after certain conditions are met. Watch this video; it tells you exactly what the computer does and when; it's fascinating!
 

80mirada

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Electronic Lean Burn is an ignition control system designed to allow the engine to be tune leaner. It was very advanced for its time. Most problems with it were actually the same problems as non-ELB cars of the day, but the computer would be blamed for the problem. Sinking floats and stuck needle valves, bad coils, plug wires and all sorts of other problems would be diagnosed as a problem with the controller or a sensor. My parents has a 76 Chrysler wagon that not a single "mechanic" could diagnose for a starting problem. Three ELBs, a distributor, two TPSs and all new vacuum lines later, the car still had the same problem. The problem was bad floats, and needle and seats in the Thermoquad. It was a common problem on non-ELB cars, but not one of the idiots at the local dealer thought to diagnose by symptoms, or read the service bulletins.

A friend of mines dad was called "the Witch Doctor" because he could fix computer controlled cars without the special diagnostic equipment. He simply followed the same diagnostic procedure whether it was computer controlled or not.
 

Cordoba1

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Mopar had the right idea starting in the 1970's with the Lean Burn and Electronic Spark Control but at that time the computer technology wasn't there to make it work really well yet. I don't mean that it didn't work, just that it could have worked a whole lot better with more and faster computing power.

The 70's versions were not as sturdy as the later units, but it was used all the way through model year 1989. I turned out to be pretty reliable and the system was unlikely to strand you. The system found it's way onto both Slant Sixes (rare) and lots of carbureted Chrysler 4 cylinders on the early K-cars (and their kin.) One of the problems, in my opinion, was the lack of knowledge to keep the system working properly. I've learned that even Chrysler mechanics of the era didn't get real good factory training. I've fixed several of these, and the system will often go into limp mode when the $9 coolant temp switch shorts to ground. There are more of these videos out there that show how to properly diagnose the sensors. Get into a properly fettled, perfectly working 1980's M, and drivability is good from cold start to hot idle.
 

Cordoba1

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Electronic Lean Burn is an ignition control system designed to allow the engine to be tune leaner. It was very advanced for its time. Most problems with it were actually the same problems as non-ELB cars of the day, but the computer would be blamed for the problem. Sinking floats and stuck needle valves, bad coils, plug wires and all sorts of other problems would be diagnosed as a problem with the controller or a sensor. My parents has a 76 Chrysler wagon that not a single "mechanic" could diagnose for a starting problem. Three ELBs, a distributor, two TPSs and all new vacuum lines later, the car still had the same problem. The problem was bad floats, and needle and seats in the Thermoquad. It was a common problem on non-ELB cars, but not one of the idiots at the local dealer thought to diagnose by symptoms, or read the service bulletins.

A friend of mines dad was called "the Witch Doctor" because he could fix computer controlled cars without the special diagnostic equipment. He simply followed the same diagnostic procedure whether it was computer controlled or not.

YES! To all of this.
 

Justwondering

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Thanks to everyone for the knowledge.
This goes a long way to explain why having replaced only 4 vacuum lines so far, my car's idle has smoothed out and it no longer dies when I put it in reverse.

My favorite is WOT - Wide Open Throttle ... sounds like my dog first thing in the morning...

I still have 2/3rds of the engine to clean up and replace hoses/vacuum lines, which should lead to more improvements on cold start and hill climbing.

My takeaway is:
1. there are plenty of sensors (some more and some less sophisticated)
2. just like my cranky ford dually, those sensors are there to help save the engine
3. without a dataport (like in the ford dually) the diagnostics on the chrysler are not accomplished by looking at a computer screen and software
4. paying attention to symptoms, walking through the service manual diagnostics methodically will go a long way to solving most problems
5. if it walks like a duck and talks like a duck, its usually a duck even if it has a computer

AJ/FormS:
You know, the earth isn't really a globe.. more egg shaped. If you would just go out to Area51, they can explain all the details to you after the mothership arrives to take you through the wormhole which you can only do if you DO NOT step through the stargate while at Warehouse 13 in Area 51.
 

Aspen500

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Area 51 is only a scheme concocted to prevent the public from discovering the REAL base that the aliens and recovered spaceships are kept which is,,,,,,Area 52.
As out there as that sounds, you all know how our government operates and it could very well be true.

Even with a data port (also known as the data link connector), all a scanner gives you is fault codes and parameter data on the inputs and outputs. It's up to the person working on it to diagnose the actual cause. Is it a bad sensor, a fault in the wiring, a fault in the ECM? Also, the fault code could be caused by something seemingly unrelated to what the code refers to. Sometimes it's an obvious fix, other times you're digging in deep to find the cause and a fault code isn't necessarily an electrical fault. It could also be cause by a base engine problem among other things. Lately it's been "P0016 Cam/Crank correlation error" on the GM 3.6L V-6 and the GM 2.2L Ecotech 4 cyl and it has nothing to do with any electrical or electronic fault. Lets just say they didn't use the best timing chains and guides in the world. Chains stretch, cam timing gets too far off and the cam sensor and crank sensor correlation is out of range (I think the tolerance is 4 degrees either way, max)and the check engine light comes on (along with the obvious like loss of power, rough idle, rattling noise noise). I actually enjoy doing them and also call them "job security". See what I deal with everyday at work? That's why us auto tech's get paid the big bucks (I wish), lol.
 

Justwondering

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aspen500 --
I'll keep you in mind as I continue to troubleshoot my ford dually. I'm confident it is a slowly, failing mechanical part which is setting off some sensor that puts the dang thing into limp mode.

Just got the dataport dongle so I can read and reset the codes myself instead of driving 50 miles round trip to get it done.

That's my summer goal ... get the diagnosis on the ford and fix whatever is making it drive wonky.
 

Aspen500

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Who comes up with the names for these things? Dongle, Bluetooth, tweets, apps........................
Is you truck a Powerstroke or is it gas? If it is diesel and a 7.3L, very little ever went wrong with those. Most common was (is) the valve cover gasket injector harness connectors melting and the crankshaft position sensor. If it's 6.0L then,,,,,,,,,,,,,,,,my condolences! Never EVER buy a Ford Superduty with a 6.0 diesel, EVER unless you have deep pockets. What goes wrong with those? Well let's see. Injectors, injector control modules, crank sensors, cam sensors, oil coolers, egr coolers, headgaskets, egr valves, high pressure oil pumps, rocker arms, pistons, IPC valves (injection pressure control), stuck variable vane turbos, cracked/leaking y-pipes from the manifolds to the turbo..............the list goes on. Ford/Navistar went from one of the best diesels made (the 7.3) to the biggest POS since the Olds 350 diesels of the 1980's with the 6.0L in mid year 2003. Reason? The 7.3L couldn't realistically be made to meet the upcoming emissions regulations and they rushed the 6.0L out at least a year before it was ready. Sound familiar, kind of like the Aspen and Volare? One difference is, the F-body was great once it's initial teething problems were resolved where the 6.0 was junk from it's first day to it's last.
 

Justwondering

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1997 ford dually f350 diesel powerstroke superduty

we can start another thread if you want in on this mystery..

I have a strange mix of vehicles. This is my first diesel. I was rock hauling for about 18 months and it does that really well. Due to husband health issues, I had to quit that work and am on to the next thing that lets me work from home.

Ford sits tall which makes it easier to spot traffic issues.

Has 2 tanks so I never have to stop for petrol until after I have the trailer off and its easier to do.

Has dually backend so gets plenty of traction as long as you are on pavement (2wd not 4wd).

Its the last year they put the powerstroke in it... following this they went to the 6.0 craptastic engines.

Had plenty of folks offer to buy the truck but they just want the engine.
 

Aspen500

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The 7.3L Super Duty trucks are sought after by people who need a diesel but don't want a 6.0 and can't afford a newer one with a 6.7L (the 6.4 was a so-so engine). Problem is, that makes the trucks a minimum of 13 years old which in this state means most are rotted half way to the door handles..............................In other words, not a large selection to choose from anymore.
 
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