yo,
EDIT. I AM LIMITED TO 20 IMAGES NOW,
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Carbureted Broncos should have between 17 & 21 in-Hg at idle; read this Vacuum Gauge Diagnosis
Vacuum Leak Test; On an idling engine check for vacuum leaks using a mechanic's stethoscope, or a ~3' garden hose section.
On COLD ENGINE only, use propane torch w/rubber hose attached, UNLIT or spray carb cleaner, when it gets to the the leak the RPMs will rise.
Vacuum Gauge Diagnosis by Craig @
Reading your vacuum gauge
Suggest buying a vac gauge, best low cost test and MPG helper you can spend $ on;
pic; "...I have a vacuum gauge mounted right in the dash of my truck. I use it to also help determine the load my engine is under while driving, and to estimate fuel economy..."
Source: by William T at
http://www.fordf150.net/images/mytruck/vacgauge.jpg
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EFI Broncos
Borrow or purchase a vacuum gauge and read this Vacuum Gauge Diagnosis @
1996 Bronco/F-Series
Similar to other EFI years.
One way to do a quick check is to grab a vacuum gauge. Some parts stores will loan you a gauge with refundable deposit.
The vacuum gauge should read between 15 and 22 in-Hg depending upon the engine condition and the altitude at which the test is performed. SUBTRACT ONE INCH FROM THE SPECIFIED READING FOR EVERY 1,000 FEET OF ELEVATION ABOVE SEA LEVEL.
The reading should be quite steady. .
When engine is rapidly accelerated (dotted needle), needle will drop to a low (not to zero) reading. When throttle is suddenly released, the needle will snap back up to a higher than normal figure.
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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EFI High Idle Tips by Mikey 350:
"Take off the air intake hoses so you can access the throttle bores. Start the engine and place a piece of stiff cardboard over the throttle bores. That should NOT change a correctly configured engine, as the idle air is only from the opening of the IAC, and nothing through the throttle bores.
If that make a difference, then the throttle plates are slightly open due to the removal of the Teflon coating, or the linkage/return spring/throttle stop is screwed up.
If the engine still runs too fast with the throttle opening blocked, try taking off the IAC and blocking those openings.
What you have done is (supposedly) removed all the "normal" air intakes, and if the engine still runs, you have a vacuum leak.
You could then try leaving the air intakes (throttle and IAC) blocked and cap off the vacuum lines coming off the vacuum tree. (except the MAP line) If one of those makes a difference, investigate the leak.
Check the vacuum line from the vapor canister (on the left side of the throttle, when facing the throttle assembly) (cap it, on the outside chance that the solenoid has failed open) (if equipped)
Pull the EGR connection to the intake and plug or cover it. (if you have wide duct tape, use that to cover the hole)
If it still is running with the throttle blocked and the IAC and the lines from the vacuum tree capped, then you have a manifold or PCV line leaking. Plug the PCV line to the intake, then the vacuum line to the brake booster (if it has it's own fitting on the manifold)
Something is causing that high idle, and 95% of the time it is a vacuum leak."
...
Quick Vacuum Leak Test; On an idling engine check for vacuum leaks using a mechanic's stethoscope, or a ~3' garden hose section. Beware of fan, belts, pulleys & Hot hoses and engine.
On COLD ENGINE only, use propane torch w/rubber hose attached, UNLIT, when it gets to the the leak the RPMs will rise.
.
Also check vacuum hoses & vacuum operated components, such as:
Intake plenum gasket leak on the passenger side and on firewall side is a hard-to-find leak; as well as throttle body gasket; worn throttle shaft and lower intake gasket(s).
With the engine cold, visually and physically check all vacuum hoses. The most common vacuum leak problem is the PCV tube's elbow, where it connects to the intake manifold.
"... start her up and spray around the intake manifold's gaskets to check for leaks. If the carb spray hits a spot that is leaking, the engine RPM's will increase or decrease and this will pinpoint the source of the vacuum leak.
Not only will the RPMs increase or decrease, remember, you can't let the engine get hot and continue to spray the intake manifold to cylinder head areas with carb spray". by Abraham Torres-Arredondo
Vacuum tree Location pic in a 94 5.8 Source: by joelb23 at
Vacuum block, aka Tree pic on firewall at
Vacuum Block in an 86 by Chris B
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PCV damaged or vac line leak; make sure the PCV rubber elbow (at the intake manifold) is not torn or that it does not have dry-rot.
PCV pic by Bbronco311
.
PCV VACUUM HOSE PIC In A 95 by Shadofax (TheJuice, The Juice, Mark Z)
Note; use fuel-rated vacuum hose for PCV Valve.
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Emission System Vacuum Tank (VRESER, Vacuum Reservoir - looks like a coffee can in earlier years)
Location pics in a 95 5.8 (he replaced it w/Peanut can)
1995 Ford Bronco misc. pictures, videos, and sounds | SuperMotors.net
Source: by fordbronco1995 ("JUICE") He replaced it w/Peanut can because most rust out on underside or end opposite hose ports.
The Vacuum Reservoir (coffee can) stores vacuum and provides "muscle" vacuum. It prevents rapid fluctuations or sudden drops in a vacuum signal such as those seen during an acceleration period.
Diagnosis; When charged initially with 15-20 in-Hg vacuum, vacuum loss shall not exceed 0.5 in-Hg in 60 seconds. If it does, replace the reservoir.
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Vacuum Check Valve; A vacuum check valve blocks airflow in one direction and frees airflow in the other direction. The check side of this valve will hold the highest vacuum seen on the vacuum side. If not, replace it.
Diagnosis;
Apply 16 in-Hg vacuum to "check" side of valve and trap. If vacuum remains above 15 in-Hg for 10 seconds, the valve is acceptable.
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The EVP EGR Valve is required in EEC systems where EGR flow is controlled by the Powertrain Control Module (PCM) through an EGR Valve Position (EVP) sensor attached to the valve. The valve is operated by a vacuum signal from the EGR Vacuum Regulator (EVR) Solenoid (9J459) which actuates the valve diaphragm.
As supply vacuum overcomes the spring load, the diaphragm is actuated. This lifts the pintle off its seat allowing exhaust gas to recirculate (flow). The amount of flow is proportional to the pintle position. The EVP sensor mounted on the valve sends an electrical signal of its position to the PCM.
Source: by SeattleFSB (Seattle FSB)
miesk NOTE: EVP is used on all years except for 95 5.8L California models & all 96, they use the DPFE Sensor instead of EGR Valve Position Sensor (EVP)
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Differential Pressure Feedback (DPFE) Location pic in a 96 5.0; Silver Rectangular item, driver's side next to distributor
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EGR Vacuum Regulator (EVR); also called EGR Vacuum Solenoid is an electromagnetic device which controls vacuum output to the EGR valve. An electric current in the coil induces a magnetic field in the armature which pulls on a disk closing the vent to atmosphere. The Powertrain Control Module (PCM) outputs a duty cycle to the EVR which regulates the vacuum level to the EGR valve. As the duty cycle is increased, so is the vacuum signal to the EGR valve. The vacuum source is manifold vacuum.
EGR Vacuum Regulator (EVR); Location pic in a 90 5.8
Source: by SeattleFSB (Seattle FSB)
"Resistance across the terminals should be 20-70 ohms" by Tomco
Thermactor Air Bypass Solenoid (TAB, AIRB, AM1) w/Pink vacuum line & Air Bypass Valve (AIR BPV) & Thermactor Air Diverter Solenoid (TAD, AIRD, AM2) w/Yellow vacuum line & Air Diverter Valve or Air Control Valve (ACV) Location pic in a 90 5.8; "...Be advised that the ACV (Air Control Valve) is the TAD (Thermactor Air Diverter) Valve and the AIR BPV is the TAB (Thermactor Air Bypass) Valve. The VRESER is the Vacuum Reservoir Can where the red & black vacuum lines plug into; On my 1990 ex-5.8L, the Yellow Vacuum Line goes from the TAD Solenoid (driver's side forward solenoid) to the TAD (Diverter) Valve located at the rear of the Intake Manifold on Crossover (aka "Y") tubing.
... You have to climb up onto the engine to feel the Diverter Valve or remove the Intake Manifold. I'd rather climb up using plans, ala a scaffolding type set-up; maybe remove hood depending on circumstances such as me now, w/ backache..."
TAB
Source: by Seattle FSB (SeattleFSB) ...
"The Yellowish line and pink line goes to the TAB/TAD valve on the back of the motor."
pic by JOWENS
Check vacuum hose; & valves for damage
Later years used a combination TAD/TAB Valve on Crossover tube
Depiction by Seattle FSB
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HVAC System (AC, heater, defroster), vent control ckt & vacuum tank (plastic ball, or an irregular box glued to the evaporator cover), under dash & lines to heat/blend/etc. doors; & HVAC vacuum reservoir.
Check Valve & Tank Location pic in a 93; "...valve is about a foot down the vacuum line coming off the 'tree' on the engine Plenum. One of the lines on the check valve tee goes to the built-in reservoir on the a/c box, the other into the loom with the white tube heading for the control panel inside ..."
Source: by garymunson at FSB
"...The air handling system is designed to provide defrost when no vacuum is applied to any of the three air door vacuum motors. This is done to prevent a situation where defrost cannot be obtained due to a system vacuum leak. Instead, a leak in the vacuum control circuit will send all airflow to the defroster outlets. This condition may occur during acceleration (slow leak), may exist at all times (large leak) and may happen only when certain specific functions are selected, indicating a leak in that portion of the circuit. ..." by Ford
Look on passenger side, firewall/ inner fender liner corner; inspect the Outside Air/Recirculated Air Door Vacuum Motor & vac line
Outside Air/Recirculated Air Door Vacuum Motor Mini-Tube Vacuum Hose Damage Repair in a 92, similar to earlier years & 92-96
Source: by JohnMcD348
pic by Steve83 (BANNED)
HVAC System Vacuum Tank (plastic ball type) Location & Carbon Canister (Charcoal, Vapor, Evaporative Emission (EVAP) & Vacuum Hose Routing Video in an 86 5.0
Source: by JKossarides ("The Bronco", Jean)... RIP BRO! ...at
1986 Ford Bronco my flip video library video | SuperMotors.net
HVAC System Vacuum Tank (plastic ball type) in 80-86 vacuum tank is a plastic ball on the R wheel well..." Source: by Steve at
1983 Ford Bronco Diagrams picture | SuperMotors.net
HVAC Vacuum Diagram in a 95 by fordbronco1995
"...80-91 similar, except 87-early 88 w/factory air..."
Look under dash glove box area @ vac motors, vac lines and control panel for leaks.
Can pull lines off of control panel and test with hand held vacuum pump with gauge, aval. @ parts stores loan a tool program.
Control Panel; "If you pull the AC controls from the dash and look on the back of the switch with OFF, you find it has a vacuum connection that is held on by 2 special washers. If the plastic peg breaks, or the washer comes off, the vacuum manifold end can pull away from the switch and cause a leak. The switch can also break causing a leak in the switch itself." by jowens1126 in a 94.
"Under the dash is a vacuum line bundle, it comes thru the firewall, then into a large multiport connector, then the lines go the the selector switch on the back of the control panel. The Big multiport connector could come loose and cause a leak. Its the biggest connector here with yellow lines coming off of it." by jowens1126 See more pics & info by jowens @
Vacuum Leak in A/C Control ?...
Evaporative Emission (EVAP) Canister for the Evaporative System (aka Charcoal Canister, Vapor Canister, Carbon Canister) pic @
https://www.fullsizebronco.com/attachments/corrsoion-box-jpg.15892/ by td152
Note; use fuel-rated vacuum hose for Canister purge solenoid (CanP)
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CanP vacuum hose to throttle body in a 96 pic by edamanski @
https://www.fullsizebronco.com/cdn-...zebronco.com/attachments/download-jpg.151992/
Cannister Purge Solenoid (CANP) pic @
1990 Ford Bronco Emissions picture | SuperMotors.net
by SeattleFSB
...
Power Brake Booster;
Inspect line to & the power brake booster; defective booster. Inspect power brake booster check valve, rubber grommet and all vacuum plumbing for cracks, holes, bad connections or missing clamps.
Fuel Pressure Regulator (FPR); pic in a 90 (same for all V8 EFI years) @
1994 Ford Bronco Fuel Pressure Regulator replacement picture | SuperMotors.net. by 94xlt
Leaky O-rings around the fuel injectors allow air to leak past the seals.
Manifold Absolute Pressure Sensor (MAP) Sensor Location pic in mid 80s @
1988 Ford Bronco technical stuff picture | SuperMotors.net by jejm270
the "right side" (passenger) near the EEC Test Connectors
vacuum hose; ; if good, check vacuum levels w/gauge because Ryan M (Fireguy50) wrote; "...The sensor changes frequency relative to intake manifold vacuum. The sensor frequency increases as vacuum increases..."
Fuel Injection Technical Library » Manifold Absolute Pressure Sensor (MAP)
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See
Seattle FSB's Comprehensive Vacuum Test and Component article @
Possible vacuum issue/lobing idle when warm
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A Vacuum Gauge is
best low cost test and MPG helper you can spend $ on;
pic; "...I have a vacuum gauge mounted right in the dash of my truck. I use it to also help determine the load my engine is under while driving, and to estimate fuel economy..."
by William T at
https://www.fordf150.net/images/mytruck/vacgauge.jpg
This Gas Saver Vacuum Gauge may be able to be mounted in dash, but it looks like an under mount;
@
https://www.autoparts2020.com/parts-master/gas-saver-vacuum-gauge-pmp-pm1520
Full swing gas saver, OEM size gauge w/panel.
Heavy duty, shock protected movements
All metal cases, wide triple chrome plated bezels
OEM style backlit illumination
Work on 12 volt neg. ground systems, 4-6-8 cylinder engines
Unconditional 10 year warranty $20.09 Part #: PM1520 Size: 2 in
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Vacuum Diagram Color Codes: not all apply to your year:
Red = Main vacuum
Green = EGR function
Orange = Heat control Valve (exhaust & intake) (AKA heat riser but more complex)
Yellow = Distributor advance
White = EGR vacuum (source)
Black = Mainly used for the Evaporative emissions control
Black = Thermactor ACV or Diverter valve
Blue = Throttle Kicker control
Pink = TAD to Thermactor Air Bypass Valve (TAB or AIR BPV) /AIR Bypass (AIRB) valve
NOTE: AIR BPV is the AIR Bypass (AIRB) Valve; also called the TAB (Thermactor Air Bypass) Valve in other years/diagrams
See your Vacuum Diagram; (not including HVAC system) under hood or atop radiator support,
aka Vehicle Emission Control Information (VECI), PUK (49 States) Decal, PGP (Canada) Decal
Vacuum Line Acronyms:
TAB is the Thermactor Air Bypass Solenoid
TAD is the Thermactor Air Diverter Solenoid
ACV (Air Control Valve) is the TAD (Thermactor Air Diverter) Valve (AIR Bypass (AIRB) and AIR Diverter (AIRD) valve combinations);
MAN VAC is Manifold Vacuum;
FPR is Fuel Pressure Regulator;
EGR is Exhaust Gas Re-circulation Valve and/ or EVR is EGR Vacuum Regulator
SOL V: Thermactor Air Diverter (TAD) Solenoid (SOL V) (AIRD) & Thermactor Air Bypass (TAB) Solenoid;
VMV is Vapor Management Valve ; located on passenger side firewall, high in our 96 5.0L; miesk5 note; for OBD II, The vapor management valve (VMV) replaces the canister purge valve used in EEC IV
VRESER is the Vacuum Reservoir Can (Tank, aka coffee can that 7often rusts out on bottom;
V REST on later years is Vapor Valve atop fuel tank; runs forward to Carbon Can (Carbon Canister, (Charcoal Canister, Vapor Canister, Evaporative Emission (EVAP) Canister);
CPRV is Canister Purge Solenoid Valve/ Canister Purge Solenoid (CANP); from canister to throttle body,
MAP is Manifold Absolute Pressure Sensor;
AIR BPV is the AIR Bypass (AIRB) Valve, also called the TAB (Thermactor Air Bypass) Valve;
VCKV is Vacuum Check Valve;
PCV is Positive Crankcase Ventilation Valve
MAN VAC is Manifold Vacuum
CAT is the catalytic converter
ENG is the engine
Vacuum Diagram Color Codes: not all apply to your year:
Red = Main vacuum
Green = EGR function
Orange = Heat control Valve (exhaust & intake) (AKA heat riser but more complex) for carbureted years
Yellow = Distributor advance for earlier years
White = EGR vacuum (source)
Black = Mainly used for the Evaporative emissions control
Black = Thermactor ACV or Diverter valve
Blue = Throttle Kicker control for carburetors
Pink = TAD to Thermactor Air Bypass Valve (TAB or AIR BPV) /AIR Bypass (AIRB) valve
NOTE: AIR BPV is the AIR Bypass (AIRB) Valve; also called the TAB (Thermactor Air Bypass) Valve in other years/diagrams
See your Vacuum Diagram; but it does not include HVAC system under hood or atop radiator support
aka Vehicle Emission Control Information (VECI), PUK (49 States) Decal, PGP (Canada) Decal
Acronyms, Carbureted:
(not nec. for your year/engine)
A/CL: Located in the air cleaner
A/CL DV: Air Cleaner Diverter Valve
A/CL BI MET: Air Cleaner Bi-Metallic Valve
A/CL CWM: Air Cleaner Cold Weather Modulator
ACT: Air Charge Temperature Sensor, prior to 1992
ACTS: Air Cleaner Temperature Sensor
ACV: Air Control Valve or Air Cleaner Heat Stove Vacuum Motor
AIR: Thermactor, short for Thermal Reactor. CA vehicles are installed with it as standard. Air Injection Reaction is what it stands for.
AIR BPV: AIR BPV is the AIR Bypass (AIRB) Valve; also called the TAB (Thermactor Air Bypass) Valve
BV: Bowl Vent (on top of the float tanks)
CARB: Carburetor
CBD: Closed Bowl Distributor
CPRV: Canister Purge Valve
DIST: Distributor
DV-TW:Two Way Delay Valve
EFCA: Electronic Fuel Control Assembly/ (Fuel Pressure Regulator (FPR)
EGR: Exhaust Gas Recirculation Valve
EXH HCV: Exhaust Heat Control Valve
FLTR: Filter
FPR: Fuel Pressure Regulator (check vacuum line)
HEAT VLV INT: Heat Vacuum Control Valve Intake, (next to carb)
HICV: Hot Idle Control Valve
IAT: Intake Air Temperature Sensor (Air Charge Temperature (ACT), prior to 1992
IVV: Thermactor Idle Vacuum Valve
LCV: EGR Load Control
MAN VAC: Manifold vacuum-Vacuum source; usually ref. to as Vacuum Tree atop intake manifold]
PCV: Positive Crankcase Ventilation
PURGE: Vapor Canister Purge Valve
PV: Ported Vacuum
PVS: Ported Vacuum Switch (PVS) Valve
S: Spark port
SA-FV: Separator Assembly Fuel/Vacuum
SOLV: Thermactor Solenoid Valve
SV CBV: Carborator Fuel Bowl Solenoid Vent Valve
TCAC: Thermostatically Controlled Air Cleaner
TCP: Temperature Compensated Accelerator Pump
TK: Throttle Kicker
TVS: Throttle Valve Solenoid (aka Solepot, Dashpot)
or
TVS: Temperature Vacuum Switch
TVV: Thermal Vacuum Valve
or, TVV: Thermostatic Vacuum Valve (aka Ported Vacuum Switches; Thermal Vacuum Valve)
VAC: Vacuum
VCKV or V CK V or VCV: Vacuum Check Valve
VCV: Vacuum Control Valve
VDV: Vacuum Delay Valve
V CK V or VCV: Vacuum Check Valve
VOTM: Vacuum Operated Throttle Modulator
VRDV: Distributor Vacuum Delay Valve (VDV, VRDV, DV-TW)
VRDV: Vacuum Delay Valve (VDV, VRDV, DV-TW)
VRESER: Vacuum Reservoir (coffee can style in earlier years; replaced by plastic style)
VRESV REST: on earlier years such as SEABRONC's 83 is a Vacuum Restictor/delay valve, it delays vacuum for a certain amount of time
VRV: Vacuum Regulator Valve
WOT: Wide Open Throttle Valve
