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I have a 1992 Ford Bronco with a 5.8L 351 Winsor and a E4OD Trans; Recently the CEL came on but it would only stay on at idle or under 2k RPMs. It has since then got worse and now shifts hard under 2.2k RPMs and idles high when in park; 1.1k RPMs. I have been told that it's a vacuum leak and have went through just about every vac line on the motor with no success. I don't have a smoker/fog machine to test to see if it could be a minor leak at the air plenum but I can't hear or see any signs that it I feel would cause such harsh shifts or idling issues. I know it's not the TPS because if I disconnect it the RPMs change and the CEL stays. About a year before this I had a similar issue with the "EGR Sensor/Tube from the Exhaust Manifold to the Air Plenum, but I had a trusted shop fix it and haven't had issues until now; It's also partial EGR deleted/Smog Pump Delete. I've been told there are vac lines that run to the trans but can't locate them. I also had front and back ring and pinons done with posi; Although I wouldn't see that screwing it up unless there was a vac leak at the 4x4 Hubs. Any advice on how to tackle this problem would be appreciated!

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Yo OhioBronco92,
Welcome to our diy place!

Let's begin with; try a Self Test for Diagnostic Trouble Codes (DTC)s by my pal, BroncoJoe19
Post Code(s) here according to:

A helper can assist you by counting the codes. Some use their smart phones to record them.
Or ask local mom and dad parts stores if they will test it for you. The majority of parts chain stores tests just OBDII vehicles now.
Or purchase a coder reader such as;
"Innova ODB-1 and we generally recommend getting the extension cord with it, so you can work the ignition key in the cab while watching/holding the reader. It will save the codes but knowing when to go through the cycles and ensuring you get it right the first time can save time and hassle, especially if you're working on it by yourself, as most of us do." by BikerPepe`.

The E4OD does not have vacuum lines, the C6 automatic does. See this AOD, C4, C6, E4OD, Transmission Pan ID

by TurboRegency03

High idle with no applicable codes is usually caused by a vacuum leak.
We had our 96s throttle lever atop throttle body stick recently. Cleaned it and used WD 40; but don't try to lube the cable as per Ford.

See my Vacuum leak test in post #11 @ https://www.fullsizebronco.com/forum/21-noobie-bronco-tech-questions-flame-free-zone/206824-help-dtc-codes-idle.html
It includes HVAC system, etc.

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

Other perpetrators are:
Sticking throttle linkages or throttle body plate is stuck - we had this occur recently! Sprayed throttle body cleaner on linkage atop throttle body and then light coat of WD 40 on linkage. Don't try to lubricate the cable internally.

Throttle Body top view pic in an 88 5.0 by jem270

Speed Control chain is binding, if equipped
Air intake tube is damaged
Throttle body return spring is loose
Throttle body is loose
Idle Air Control Valve (IAC)

"Start the Bronco 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
Idle Air Control Valve (IAC). If the engine begins to stubble or stalls the IAC is functional and does not need to be repaired. If the engine idle does not change you should remove the IAC for inspection.

The IAC 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 IAC to function properly. Remove the IAC and clean it. There are 2 halves to the IAC, 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 IAC needs to be replaced." by Ryan M

How to Clean and Test your IAC by Seattle FSB @ https://www.fullsizebronco.com/forum/23-technical-write-ups/206960-how-clean-test-your-iac.html

TPS Overview & Testing by Seattle FSB @ TPS Overview & Testing by Seattle FSB @ https://www.fullsizebronco.com/forum/blogs/seattle-fsb/681-throttle-position-sensor-management.html
Mikey350 wrote, "Does your throttle body have a yellow warning sticker that says not to clean the throttle bores?
Try this: 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 b9dy, 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"

Harsh Shift:
E4OD Transmission Control Indicator Light (TCIL) is a LED and overdrive on/off switch at end of the Transmission shifter stalk; flashing OD light is an indication of a transmission related trouble code in the Powertrain Control Module (PCM).* Is it flashing?
Transmission will operate in a failure management mode with harsh engagements, firm shift feel, and abnormal shift schedule..."

DTC 29 & 452 Erratic Harsh Shift; PSOM Operates Correctly; "...Continuous Memory DTC 29 indicates that during the last 80 warm-up cycles, the PCM detected an error in the PSOM output signal. DTC 452 indicates the PCM detected an error in the PSOM output signal during the last 40 warm-up cycles. his procedure EXACTLY, from the Ford TSP/PCED..." READ MORE
Source: by SigEpBlue (Steve) at http://web.archive.org/web/20131015134237/http://fullsizebronco.com/forum/showthread.php?t=161210&highlight=psom

DTC 452 Erratic Harsh Shift; Short Circuits, Common Locations TSB 95-02-11 on 94-95 Bronco & Trucks; SEE C, E4OD Harsh Shifts & D, Code 452 - see Poss. Short Locations: 1. Driver's side A pillar trim screws may have been installed thru da 17K745 Sun Visor wire assy & .. bullet connector; 3. Scuff plate screws (driver's side) may pinch the 14A504 wire assy; 4 14401 wire assy may be trapped/pinched between Half car beam & instrument panel attachment (repeated as #7. the wire harness may be pinched/shorted behind the dash where the 14401 wire assy may come in contact w/a sharp edge on dash panel wall 5. shift cable assy near tranny may chaf the wire harness; the wire harness; 7. repeated above..brake pedal-to-dash panel wall weld.
Source: by Ford

DTC 522 & 654 indicate the gear selector was not in Park during Self-Test; "...Possible causes: Misadjusted linkage. Open or short in harness circuits. Damaged TR sensor. Damaged Powertrain Control Module (PCM) . OR CHECK THIS OUT, TECHNICAL BULLETIN # 230A, TRANSMISSION: E4OD SUBJECT: No upshift 4th gear starts, harsh upshifts, neutrals out after shifts APPLICATION: Ford-E/F Series, Bronco DATE: Jan 1995 NOTE: Click on image to make it larger. All of these concerns can be the result of an inappropriate Manual Lever Position (MLP) sensor signal. The MLP sensor consists of six resistors connected in series (ganged). The resistance of the MLP sensor will vary based on which range the transmission is in. The MLP circuit can be checked using the following steps. (Step 1) Check the MLPS ground: Turn the ignition on. The voltage on pin 46 (sensor ground ) should not exceed .1v. If the voltage is excessive, add an additional ground to the existing ground wire (figure 2). NOTE: Click on image to make it larger. Figure 2 Splice an additional ground from the existing ground wire to a known good ground.The negative post of the battery is the best. This view is of the pins of the MLP connector pins. NOTE: Click on image to make it larger. (Step 2) Check the MLPS voltage: The voltage at pin 30 should vary-in increments- according to the position of the manual lever (figure 3). MLP voltage (ignition on) should be within 20% of these specifications. Note It is recommended that you use a break-out box. If a break-out box is not available, you will need to pierce the wires to pins 30 and 46 for these tests. NOTE: Click on image to make it larger. (Step 3) Check the resistance of the MLPS: The resistance of the MLPS (pins 30 and 46) should change-in increments-with the position of the manual lever (figure 4). Note If this test is being done with a break-out box, disconnect the computer first (make sure the ignition is off). If this test is being done without a break-out box, disconnect the MLPS from the vehicle harness. Note Testing beyond this point will include tests of the harness. Consult the appropriate repair manual for this..."

PSOM & Odometer Not Working & E4OD Harsh Shift TSB 94-09-12 for 94 Bronco & F Series; "...PSOM (Programmable Speedometer/Odometer Module) may be inoperative or not function properly and the #8 fuse may be blown. In addition, if the vehicle is equipped with an E4OD transmission, it may exhibit a harsh shift. These conditions may be caused by trim screws installed through the 17K745 visor wire between the left hand "A" pillar and the left hand visor bullet connector..."
Source: by Ford

DTC 624, 625, P1746, P1747 The Electronic Pressure Control solenoid is a variable force solenoid. The variable-force type solenoid is an electro-hydraulic actuator combining a solenoid and a regulating valve. It supplies electronic pressure control which regulates transmission line pressure and line modulator pressure. This is done by producing resisting forces to the main regulator and the line modulator circuits. These two pressures control clutch application pressures. Failed off — maximum electronic pressure control pressure, harsh engagements and shifts. May flash transmission control indicator lamp. CAUTION: The electronic pressure control pressure output from the variable force solenoid is NOT adjustable. Any modification to the electronic pressure control solenoid will affect the transmission warranty. (*Output circuit check, generated only by electrical condition.) Possible causes, Damaged harness connector. Damaged EPC solenoid. Damaged MLP sensor. Intermittent harness continuity. Damaged PCM connector pins. Pin Point testing; READ MUCH MORE
Source: by Ford

DTC 632 O/D Cancel switch, Overdrive cancel switch did not change state during KOER; is possibly the result of the test being done incorrectly. When you do a KOER test, you need to do a Dynamic Response Check is used to verify operation of the Throttle Position Sensor (TPS), Mass Air Flow (MAF), Manifold Absolute Pressure(MAP), and Knock Sensor (KS) during a brief wide open throttle condition. The famed "Goose test".

Manual Lever Position/Transmission Range (MLP/TR) Sensor - E4OD Controls Overview, Sensors, DTC (s) & Diagram; "... The powertrain control module sends voltage to the Transmission Range (TR) sensor. The TR sensor incorporates a series of step-down resistors which act as a voltage divider. The powertrain control module monitors this voltage which corresponds to the position of the gearshift selector lever (P, R, N, (D), 2 or 1). The powertrain control module uses this information to determine the desired gear and electronic pressure control pressure. The TR sensor is located on the outside of the transmission at the gearshift selector lever. Harsh engagements, firm shift feel. DTC 634, 654, 667, 668, P0705, P0707, P0708, P1705..." READ MUCH MORE
Source: by Ford
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