Yo refe1,
WELCOME!
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Parking Brake:
Switch for indicator light probably needs adjustment, it's mounted on parking brake bracket
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Idle:
Try unplugging the Idle Air Control (IAC)
IAC Location pics & Cleaning by Bobby (blue) in a 93 @
http://www.supermotors.net/registry/3982/17193-2
Testing..
"First let me say this little thing has many names. But they all talk about the same item under the hood. Here all the names I've had the torture of learning throughout the years:
•Idle Air Bypass •Idle Air Control •Idle Speed Control •Throttle Bypass Air •Idle Bypass •Inlet Air Controller
•Inlet Air Bypass •Intake Air Bypass •Intake Air Control.
This is really easy to test. First as with all problems you should gather the trouble-codes from the computer. Follow the codes for testing and repair. If you get a code that points to a problem with the IAB start the vehicle and bring the engine up to operating temperature. Allow the engine to idle without any driver input to the throttle or pedal. Go under the hood, and disconnect the electrical connector to the IAB. If the engine begins to stubble or stalls the IAB is functional and does not need to be repaired. If the engine idle does not change you should remove the IAB for inspection.
The IAB can pass and still need repair, or it can fail and not need replacing. The plunger and internal spring can get clogged with dirt and oil. This will slow down the air flow and not allow the IAB to function properly. Remove the IAB and clean it. There are 2 halves to the IAB, and you can not buy just one half, but you can take it apart to clean it. But if the internal solenoid is faulty the IAB needs to be replaced." By Ryan M.
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This is by Nelbur; "I have spent some time this week trying to set up an air bypass around the IAC valve by cutting away some of the gasket between the IAC in and out air holes, rather than pay big bucks for Fords spacer kit. I cut away the center of the original IAC gasket from the outside of each hole to the outside of the other hole, giving about 1/2" gap for the air to pass through. I noticed an immediate improvement in the engines starting behavior, but it would still die occasionally.
It
would rev up and then drop the idle so low it would die unless I would catch the idle with the accelerator. ... ...
I decided that more improvement could be had if I had a thicker gasket, because the original IAC gasket was very thin (0.018"). I had some 0.030" gasket material so I made my own with the same 1/2" cut out. This gave enough bypass to noticeably raise the idle speed and almost eliminate the dying. After maybe 50 starts in the last few days, it only died twice. After so many years of catching it with the accelerator it is darned hard to leave my foot off it. It is clear to me that by trial and error one can tune the air bypass without the need for the expensive Ford kit. I may combine the two gaskets for more bypass, but the idle is about as fast as I would want now, especially for driving in snow."
Idle Air Control (IAC) Sludge; Poor Idle TSB 91-25-07 for 85-92 Bronco & F Series & many others; "...Hard cold starts, hesitation and stalls on initial start-up or during idle or decel may be caused by sludge in the throttle body and/or idle by-pass valve. Sludge deposits or oil film on the throttle body bore and plate or the idle air by-pass valve may cause one or more of the following conditions. Hard Cold Start, Stall On Initial Start-Up, Stall During Idle, Stall During Decel,
Rough Idle, Rolling Idle, Hesitation During Acceleration. A new idle air by-pass service kit (F2PZ-9F939-A) is now available for service use to correct sludge contamination concerns of the throttle bore and plate only. It eliminates the need to clean the majority of past model throttle body applications. Cleaning is not required on sludge tolerant throttle body designs released for 1991 and newer model years..."
Buy a Motorcraft IAC in event it needs to be replaced
See my Vacuum leak test in post #11 incl some jowens126 HVAC Control Panel pics/info @
https://www.fullsizebronco.com/threads/help-with-dtc-codes-and-idle.206824/
One tip in it is, When vacuum leaks are indicated, search out and correct the condition.
Excess air leaking into the system will upset the fuel mixture and cause conditions such as rough idle, missing on acceleration, or burned valves. If the leak exists in an accessory unit, such as the power brake, the unit will not function correctly. Or Air Conditioning when in MAX mode may switch to Defrost.
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Codes:
DTC 32 typically means that the EGR valve is not fully seated. This can be due to a bad EGR valve, vacuum trapped in the EGR hose, a clogged EVR filter, or a bad EVR solenoid. It is also important to note that if you have an exhaust ventilation system hooked up, that this can also cause an inaccurate reading. Try disconnecting the system and retesting...".
JOwens has an easier test, "all you really need is a piece of vacuum tube. remove egr valve, attach vacuum line, suck on the open end, look at the bottom of the egr valve to make sure the pintle moves and hold vacuum on the line to make sure it doesnt leak down and close. thats pretty much all you need to do there. You can clean the insides up with brake kleen to get all the gunk out of it. It will make it move alot easier."
View attachment 151118
EVR, TAD, TAB pic by Seattle FSB
EVR Testing, Ford; "....check the filter on the solenoid (Fig. 4, EVR filter shown). If this is clogged it will inhibit the venting of the solenoid; "...EVR Solenoids should be 20 to 70 ohms (100 to 135 ohms for 7.5L engines). A functional test can be performed on most applications by using a Scan Tool. Enter the Output State check and cycle the accelerator pedal. This will turn all the solenoids on and off. Using a DVOM monitor the voltage at the EGR solenoid(s). They should toggle from a high voltage to a low voltage. Typically this is stated in the manuals and scan tools as above 10.5 volts to below 2 volts. If the voltage does not toggle make sure that you have system voltage on the power side of the connector. If system voltage is present and the voltage does not cycle to the low side check the connector and wiring to the PCM. If the wiring and connector are okay the problem may be in the pin at the PCM or the driver in the computer itself..." READ MUCH MORE by Tomco.
DTC 33 is triggered when the EVP sensor is not closing;
Testing & Operation; "...The EGR Valve Position (EVP) sensor monitors the position of the EGR valve pintle. The EVP sensor converts the mechanical movement of the pintle into an electrical voltage signal which is relayed to the PCM. The EVP sensor is a linear potentiometer in which resistance varies with the EGR valve pintle movement.
Voltage is fed to the EVP by the signal return circuit. As the EGR is opened the EVP directs more voltage to the EEC and less down the voltage reference circuit. The EVP sensor provides the PCM with information on EGR flow and EGR system failures. The EVP should read between 0.24 and 0.67 volts at idle with a closed EGR valve..."
EVP Test @
https://www.fullsizebronco.com/foru...-position-evp-sensor-testing-replacement.html by SeattleFSB
View attachment 151119
EVP & EGR Location pic in a 90 by SeattleFSB
DTC 41:
TSB 91-12-11 Catalytic Converter Diagnosis
Publication Date: JUNE 12, 1991
LIGHT TRUCK: 1986-91 BRONCO, ECONOLINE, F-150-350 SERIES
1988-91 F SUPER DUTY, F47
ISSUE: Lack of power or a no start condition may be diagnosed as an exhaust restriction caused by a plugged catalytic converter. A plugged catalytic converter (internal deterioration) is usually caused by abnormal engine operation.
ACTION: Diagnose the catalytic converter to confirm internal failure. Refer to the Catalyst and Exhaust System Diagnostic Section, in the Engine/Emissions Diagnostic Shop Manual and the following procedures for service details.
SERVICE PROCEDURE
1. Lack of proper HEGO operation may cause, or be the result of a rich or lean fuel condition, which could cause additional heat in the catalyst. Perform self test KOEO and KOER, service any codes.
NOTE: IF TWO DIGIT CODES
41, 42, 85 OR THREE DIGIT CODES 171, 172, 173, 179, 181, 182, 183 AND 565 ARE RECIEVED, CHECK FOR PROPER HEGO GROUND.
If the HEGO ground is good, the following areas may be at fault:
- Ignition Coil
- Distributor Cap
- Distributor Rotor
- Fouled Spark Plug
- Spark Plug Wires
- Air Filter
- Stuck Open Injector
- Fuel Contamination Engine OIL
- Manifold Leaks Intake/Exhaust
- Fuel Pressure
- Poor Power Ground
- Engine Not At Normal Operating Temperature
- HEGO Sensor
2. Spark timing that is retarded from specification may increase exhaust gas temperature and shorten catalyst life. Refer to the following procedure for service details.
a. Check spark timing. Check base timing with spout disconnected. Set base timing to the specification on the vehicle emission decal.
b. Check computed timing with spout connected.
NOTE: COMPUTED TIMING IS EQUAL TO BASE TIMING PLUS 20° BTDC ± 3°.
3. Misfiring spark plugs may cause an unburned fuel air mixture to pass through the catalyst, which could cause higher than normal catalyst temperatures. Refer to the following procedure for service details. Check secondary ignition, hook the vehicle up to an engine analyzer and check for a secondary ignition misfire.
NOTE: SERVICE ANY ITEM THAT IS NOT PERFORMING AT PROPER SPECIFICATIONS BEFORE CONTINUING.
4. Fuel pressure that is too high may cause rich air fuel mixtures to pass through the catalyst which could cause higher than normal catalyst temperatures. Refer to the following procedure for service details.
a. Check fuel pressure, install fuel pressure gauge, start and run the engine at idle. Fuel pressures between 28 and 34 PSI are typical (4.9L typically is 15 PSI higher).
b. Disconnect the vacuum line going to the fuel pressure regulator. Fuel pressure typically jumps to 40 PSI ± 3 PSI (4.9L typically is 15 PSI higher). Visually inspect vacuum line for raw fuel.
NOTE: FUEL PRESSURES ABOVE THESE VALUES SHOULD BE CORRECTED. HOWEVER, THIS MAY NOT BE THE CAUSE OF THE CONCERN. SERVICE AS NECESSARY.
5. Throttle plates in the throttle body not returning to the proper closed position may cause excessive catalyst temperatures during downhill grades. Refer to the following procedure for service details. Visually inspect the throttle body and linkage for:
- Binding or sticking throttle linkage.
- Tight speed control linkage or cable.
- Vacuum line interference.
- Electrical harness interference.
NOTE: AFTERMARKET GOVERNORS, THROTTLE LINKAGE AND CABLES ASSOCIATED WITH POWER TAKE-OFF UNITS, MAY ALSO INTERFERE WITH PROPER THROTTLE RETURN. SERVICE AS NECESSARY.
6. It is extremely important that all systems related to the engine and emission systems operate properly.
a. Visually inspect the engine compartment to make sure all vacuum hoses and spark plug wires are properly routed and securely connected.
b. Inspect all wiring harnesses and connectors for insulation damage, burned, overheated, loose or broken conditions.
c. Verify proper operation of the thermactor system. Thermactor systems that fail to dump thermactor air to the atmosphere properly or at the correct time can cause high catalyst temperatures.
d. Visually inspect thermactor system for damaged or kinked hoses and perform a function test on following components: air control valve, check valve, silencer, filter and the air bypass solenoid.
e. Verify proper operation of the engine cooling system thermostat.
➡DTC 87 - FP relay circuit failure; suspect inertia switch, fusible link, FP relay
KOEO Fuel pump primary circuit failure. When the FP relay was activated by the EEC, voltage was not detected on the control circuit.
"...This code relates to low or no power reaching the fuel pump. Start testing at the fuel pump relay. The relay must respond to the EEC processor and the relay contacts must be a low resistance path for fuel pump power. Relay testing can be done in a couple minutes with the fuel pump test table.
Fuel pump relay testing;1. Use solenoid test at EEC pin 22 to check relay coil current draw. 2. Voltage at pump power terminal must be within .5v of battery power when relay is turned on with amp meter at pin 22. Check power from battery if voltage is low. Check the inertia switch and fuse if battery voltage is missing. Pin 22- (light blue-orange) Grounded to turn "on". Voltage will drop to about 1v when "on". Current draw will be 160 to 270mA Pin 8- fuel pump monitor (dark green-yellow) 0v engine off, battery voltage with engine running..."
Source: by Dustin S (Dustball, Mellow Yellow, Mr. Laser Boy)
➡DTC 95.
Fuel pump: open, bad ground or
always on or "
always "priming""
95 in KOEO & Continuous Memory is a test which EEC performs before it energizes the FP relay; looking for a weak ground through the entire FP circuit
Fuel pump secondary circuit failure. The EEC senses infinite resistance to ground from the fuel pump on the Fuel Pump Monitor circuit.
Low or no power reaching the fuel pump. Start testing at the fuel pump relay. The relay must respond to the EEC processor and the relay contacts must be a low resistance path for fuel pump power.
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Check both EEC & Fuel Fuel Pump relays for socket corrosion, loose wires, etc.
EEC Relay (BROWN Connector, next GREEN FP Relay Connector Under hood behind air cleaner assy) Location pic in a 90 and all up to 91
Source: by Need4racin (The 90 Bronco, Dean) at
Inspect Inertia Fuel Cut-Off Switch.
View attachment 151120
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Here are some PCM KILLER perpetrators and other causes:
Old leaky capacitors, see
https://www.fullsizebronco.com/forum/7-1980-96-bronco-tech/294553-swapped-eec-no-more-codes.html by jowens1126
Smell around the PCM. If it smells like dead fish, it's bad.
Bad Intel 8061 chip or bad Intel 8361 memory chip
Bad Internal Voltage Regulator, see
http://www.fuelinjectedford.com/images/eec085.gif by Ryan M
Burned PCM printed circuit board circuits (brown burn marks).
Water damage from cowl leaks, ESPECIALLY if you you have wet carpet or mat near driver kick panel;
or on PCM Connector due to a bad hood seal near cowl panel, viewable with hood up.
The alternator could be generating an AC voltage spike due to bad diode(s) or supply Voltage Overloads.
I recommend bench-testing the alternator for voltage output and AC voltage ripple.
Thermal stress due to excessive heat and excessive vibration that causes sensitive parts to fail.
Bronco was jump started on reverse polarity.
Overheated PCM.
Corrosion or damage due to moisture is one of the main reasons for failure. Corrosion can enter through the wiring harness and moisture can enter by a failure in the seals in the PCM itself. This happens over a period of time (5 to 10 years) due to exposure to the elements.
EEC IV PCM Removal up to & include 87- 91 COMPENDIUM "...Remove driver's inside kick panel adjacent to pedals. It comes out through cabin." by Seattle FSB; "Should be one small metal screw holding it. Just slide it out, but be careful w/ gasket for firewall. Don't mess it up, you can reuse it." by Darth_ted_82 H "To remove it first disconnect battery & get use 10 mm socket to unbolt the wiring harness "connector from inside the engine bay. Then pull plastic kick panel from inside cab & remove the retainer clip Remove it by lifting rear slightly & wiggling it out of the "pocket" ... the firewall rubber gasket will have a pretty good grip on the connector so it will take some persuasion to free. " "You have to unplug it under the hood very low on the fire wall (10 mm socket)."
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