Fuel issues

[Paulos]

Maybe I misunderstood, but you say you're disconnecting the TPS and driving the truck? It's fuel injected, so it needs the TPS connected so it can accelerate. . Right?

 

[wildbill23c]

Maybe I misunderstood, but you say you're disconnecting the TPS and driving the truck? It's fuel injected, so it needs the TPS connected so it can accelerate. . Right?

Nope you can drive it without the TPS connected, it just won't regulate the fuel injectors like when you are coasting it cuts fuel, bypasses the EGR system as well, and a few other things, basically its in limp mode with the TPS disconnected, it'll run and drive just fine without the TPS, at least that's the information that adsm08 gave me regarding some fuel, power loss, acceleration issues I had posted about a while ago.

 

[1986RangerXL]

basically its in limp mode with the TPS disconnected

This is the perfect way to describe it, my v6 mustang with 185k on the clock feels like a racecar compared to driving the truck with no TPS lol

 

[Paulos]

Nope you can drive it without the TPS connected, it just won't regulate the fuel injectors like when you are coasting it cuts fuel, bypasses the EGR system as well, and a few other things, basically its in limp mode with the TPS disconnected, it'll run and drive just fine without the TPS, at least that's the information that adsm08 gave me regarding some fuel, power loss, acceleration issues I had posted about a while ago.

Okay. But the fuel injectors are electronically controlled. With the TPS disconnected, I would think that the only thing you're accomplishing by pressing the accelerator pedal is opening the throttle body , which allows more air into the engine. How is the ECM getting a signal (from the TPS) to increase the rate of fuel from the injectors? I'm no genius when it comes to fuel injection, but it seems to me that this is the whole purpose of the TPS; it senses the position of the throttle and sends that signal to the ECM.

Well, I just found a description of the operation of the TPS by Ford that says, "Defines engine operation mode: closed, part, or wide-open throttle". So apparently, when you disconnect the TPS you must be in wide-open throttle mode (maximum fuel through the injectors) or "part throttle mode", and you are only regulating the amount of air coming into the engine by pressing the gas pedal. Otherwise you wouldn't be able to accelerate much in "part throttle mode" or at all in "closed" mode. At least, that's the way I see it.

 

[PetroleumJunkie412]

Ford EFI System Tuning - Inside The Black Box Part 1 - Muscle Mustangs & Fast Fords

Read about how you can understand and tune your Ford EFI System - Muscle Mustang & Fast Fords

www.mustangandfords.com

This is a "must read" before trying to diagnose a faulty EEC module. Cannot find a better breakdown on how they work than this.

Seriously, take the hour to read all three. Ask questions, it's VERY dense and information heavy. But, this is the most concise explanation of how your ECM and sensor string works:






"Speed Density:
SD systems take fuel control a step further. Actual intake manifold pressure is now measured, using a Manifold Absolute Pressure (MAP) sensor, as well as Inlet Air Temperature (IAT, previously known as Air Charge Temperature, ACT, in older EEC systems), in addition to the previously sensed TPS and engine rpm. Now the ECU fuel control programming includes a desired A/F ratio table, the injector flow rates, engine cubic inch displacement (CID), a volumetric efficiency (VE) table, and the programs necessary to instantaneously calculate inlet airflow, required fuel flow (for the desired A/F ratio found in the A/F ratio table), and finally the correct injector PW.

Here's how SD works: The ECU will first sense MAP and IAT. Using the ideal gas law, it can calculate the instantaneous inlet air density (hence the "density" in SD). From the engine rpm and MAP, the ECU will look up (interpolate, if necessary) the programmed VE. Using the VE, engine displacement, and rpm, the ECU can calculate the instantaneous mass airflow into the engine. Looking up the desired A/F ratio from the base fuel table, the ECU will calculate the required mass fuel flow to achieve the desired A/F ratio. Knowing the number of injectors, and flow rating of the injectors, the ECU can calculate the required Duty Cycle (DC) for the injectors. Finally, knowing the DC and rpm, the ECU can calculate the required PW for the injectors. Whew!

Let's illustrate with an example. Let's say we have a 5.0 engine operating at a manifold vacuum of 5 in Hg., rpm of 3,000, IAT of 80 degrees Fahrenheit, desired A/F ratio of 14.6, and it has eight 19-lb/hr injectors. For these conditions of rpm and MAP, the VE table calls for 85 percent.


After 1999, Ford went to a returnless fuel system. Said system is found in any stock '03-'04 Cobra. A fuel rail pressure sensor (found on the driver-side fuel rail), monitors the fuel pressure, so the ECU can regulate the fuel pumps as necessary to maintain a constant pressure drop across the injectors.
From the ideal gas law, D = p/(RT), where D is density, p is absolute pressure, T is absolute temperature, and R is the gas constant for air. Before we can calculate the density, we need to fix the units so it all works. To save our sanity, we'll do the calculations in metric units. For the air temperature of 80 degrees F, the absolute temperature would be 300 degrees Kelvin. For an intake vacuum of 5 in. Hg, the absolute pressure would be 29.92-5 = 24.93 in. Hg. = 84.42 kPa. In metric units, R = 0.286 kJ/kg-K, the injectors would flow 8.36 kg/hr and the CID would be 0.005 m3.

So our inlet air density would be: D = 84.42/(0.286*300) = 0.984 kg/m2. Mass air flow is then: Ma = 11/42 D (VE)(CID)(RPM) = 11/42 (0.984)(0.85)(0.005)(3,000)= 6.72 kg/min. For an A/F ratio of 14.6, the fuel flow must then be: Mf = Ma/14.6 = 6.72/14.6 = 0.43 kg/min.

For eight injectors, each would need to flow 0.43/8 = 0.054 kg/min = 3.2 kg/hr. Since the injectors can flow 8.36 kg/hr when wide open, we only need an injector duty cycle DC = 3.2/8.36 = 0.385 or 38.5 percent. For a four-stroke engine (two revolutions per intake event), the time interval between intake events is t=2/rpm (in minutes) or 120,000/rpm (in milliseconds). At 3,000 rpm, the interval is then t=120,000/3,000 = 40 ms.

Finally, the required injector pulse width, PW = DC(t) = (.385)(40) = 15.4 ms. Isn't math fun?"








Also, crazy useful EEC-IV wiring diagram. Granted, for Mustang, but only a few pin differences between it and 2.9 ranger:

http://www.veryuseful.com/mustang/tech/engine/images/88-91_5.0_EEC_Wiring_Diagram.gif

 

[Dirtman]

A few pins mean the difference between it working and not working...

 

[PetroleumJunkie412]

A few pins mean the difference between it working and not working...

View attachment 37036

Should have mentioned to get a Haynes manual to spot the differences. The Haynes diagrams are terrible, but they are correct. Mine has a handwritten modified version of the Mustang one stuffed in the back.

 

[wildbill23c]

Okay. But the fuel injectors are electronically controlled. With the TPS disconnected, I would think that the only thing you're accomplishing by pressing the accelerator pedal is opening the throttle body , which allows more air into the engine. How is the ECM getting a signal (from the TPS) to increase the rate of fuel from the injectors? I'm no genius when it comes to fuel injection, but it seems to me that this is the whole purpose of the TPS; it senses the position of the throttle and sends that signal to the ECM.

Well, I just found a description of the operation of the TPS by Ford that says, "Defines engine operation mode: closed, part, or wide-open throttle". So apparently, when you disconnect the TPS you must be in wide-open throttle mode (maximum fuel through the injectors) or "part throttle mode", and you are only regulating the amount of air coming into the engine by pressing the gas pedal. Otherwise you wouldn't be able to accelerate much in "part throttle mode" or at all in "closed" mode. At least, that's the way I see it.

Trust me it will run and drive with the TPS disconnected, it just doesn't shut the fuel injectors off when you are slowing down, or coasting, like going down a hill. It provides full fuel all the time regardless of speed, throttle input, etc...which is why I said its in limp mode when you disconnect the TPS, it just runs off of the base programming in the ECM at that point.

I drove my 87 Ranger around for over an hour last week with the TPS disconnected...it don't hurt anything other than your fuel economy.

 

[1986RangerXL]

Installed the new TPS and IAC sensors tonight. I hoped to see some improvement, but it still had some surges and it would not idle down. When the engine tries to idle down, it just dies. Doesn't matter where the idle screw is set.

Yes I unhooked the battery to reset the ECM.

I did find a splice in the EGR vacuum line that I replaced.

Back at it again tomorrow to try and fix the idle.

Anyone want an 86' Ranger? haha

 

[1986RangerXL]

Okay. Did more mind-numbing digging. A couple other threads that had surging problems mentioned the wiring harness, which I did change. But why would a wiring problem only surge when the engine is cold? I don't know much but that doesn't sound right.

Do vacuum leaks lessen in severity when the engine is warm?

Some people have mentioned the MAP sensor fixed their problem. I have an '86 with an EGR. I have no idea what the EGR is or how to diagnose problems. I should look into that..

This truck has been a nightmare introdoction into the into the world of mechanics..

 

[alwaysFlOoReD]

There is NOT an idle adjustment screw! There is an anti-diesel screw which should not be touched. There is a couple recent threads that have the procedure for setting the TPS back to factory stock. @RonD has described the procedure in other threads. Search...
When the TPS is set properly then the IAC does the job of setting the idle.
TPS = Throttle Position Sensor
IAC = Idle Air Control

 

[wildbill23c]

There is NOT an idle adjustment screw! There is an anti-diesel screw which should not be touched. There is a couple recent threads that have the procedure for setting the TPS back to factory stock. @RonD has described the procedure in other threads. Search...
When the TPS is set properly then the IAC does the job of setting the idle.
TPS = Throttle Position Sensor
IAC = Idle Air Control

Yeah that screw don't do anything in the way an idle screw on a carburetor did...if you mess with what you think is the idle screw on these 2.9L engines you end up with a high idle or really low idle that the computer cannot compensate for, which is part of the IAC and TPS job from sending the signal to the ECM to tell it how to adjust the idle. Made that mistake already on mine, I have to go figure out how to readjust that non-idle screw that maybe shouldn't even be there in the first place HAHA!!

My Ranger surges when its cold too, even worse when you turn on the lights and/or the heater blower motor...it'll go away after a while if you turn the lights and blower motor off, then it'll idle normally. Turn the lights and/or blower motor on again it'll surge, but tends to only do that when cold, after I start driving it, I can turn the blower motor back on, I can usually turn the lights on after a few seconds of slightly increasing the engine speed before driving, then everything is fine. Just today I took the truck on a 30 mile drive, everything was fine till I turned off 1 highway onto another, after about a mile it started cutting out. Previously I was driving 55mph, the 2nd highway's speed went up to 65mph, that's when the cutting out issues started. I need to find a volt meter to hook up so I can monitor voltage as I have a feeling I've got a voltage issue at high speed intermittently that's causing this issue as my fuel pressures are still at 42psi when this problem arises, originally I thought I had a fuel related issue even after all of the fuel system work I did but its not the case. Mine is electrical, either alternator, ignition coil, wiring, don't know for sure yet.

 

[Josh B]

Yeah that screw don't do anything in the way an idle screw on a carburetor did...if you mess with what you think is the idle screw on these 2.9L engines you end up with a high idle or really low idle that the computer cannot compensate for, which is part of the IAC and TPS job from sending the signal to the ECM to tell it how to adjust the idle. Made that mistake already on mine, I have to go figure out how to readjust that non-idle screw that maybe shouldn't even be there in the first place HAHA!!

My Ranger surges when its cold too, even worse when you turn on the lights and/or the heater blower motor...it'll go away after a while if you turn the lights and blower motor off, then it'll idle normally. Turn the lights and/or blower motor on again it'll surge, but tends to only do that when cold, after I start driving it, I can turn the blower motor back on, I can usually turn the lights on after a few seconds of slightly increasing the engine speed before driving, then everything is fine. Just today I took the truck on a 30 mile drive, everything was fine till I turned off 1 highway onto another, after about a mile it started cutting out. Previously I was driving 55mph, the 2nd highway's speed went up to 65mph, that's when the cutting out issues started. I need to find a volt meter to hook up so I can monitor voltage as I have a feeling I've got a voltage issue at high speed intermittently that's causing this issue as my fuel pressures are still at 42psi when this problem arises, originally I thought I had a fuel related issue even after all of the fuel system work I did but its not the case. Mine is electrical, either alternator, ignition coil, wiring, don't know for sure yet.

Interesting perspective there WildBill. How do you hook it up to perform that type of test?

 

[PetroleumJunkie412]

There is NOT an idle adjustment screw! There is an anti-diesel screw which should not be touched. There is a couple recent threads that have the procedure for setting the TPS back to factory stock. @RonD has described the procedure in other threads. Search...
When the TPS is set properly then the IAC does the job of setting the idle.
TPS = Throttle Position Sensor
IAC = Idle Air Control

This needs to be written across the tb cover. Seriously.

Don't worry, I did it too once.

 

[Dirtman]

This needs to be written across the tb cover. Seriously.

Don't worry, I did it too once.

It is on mine. Along with a warning not to use carb cleaner on it.