1995 Bronco engine RPMs drop when turning the wheels... stalled this morning

[mespig]

Hi all! been reading this forum for quite a while - it's unbelievable the detailed information that gets posted! Thanks to all those who help.

I have a 1995 Bronco I've owned since new. Haven't done a lot to it besides regular maintenance. It's an XLT with a 351W and limited slip diff so yes, very low gas mileage

I've always noticed the engine go under load when turning the wheels at low speed and tight (ie. leaving the driveway or pulling into a parking space) and more apparent when the engine is cold. This morning it actually stalled so makes me think it might be time to address it. I didn't see anything on this forum but a general search turns up recommendations on the TPS, possibly a pressure switch (although this might be only on the 5.0) or just replace the power steering pump. I don't believe any codes were generated but I'll get a reader this weekend and check.

Anyone else seeing similar behavior? Thanks! Mike

 

[Tiha]

The Idle air control could very well be dirty or bad. It controls rpms at idle or low speeds. There are some quick and simple tests to do.
I am sure someone else will post it up shortly or I will go find it.

 

[miesk5]

Yo Mike,
Welcome!
Try a Self Test for Diagnostic Trouble Codes (DTC)s by my pal, BroncoJoe19 @ Code Reader
PCM stores the Self-Test program in permanent memory. When activated, Self-Test checks the EEC system by testing memory integrity and processing capability, and verifies that various sensors and actuators are connected and operating properly.
The engine temperature must be greater than 50° F for the Key On Engine Off (KOEO) Self-Test and greater than 180° F for the Key On Engine Running (KOER) Self-Test. Run it around to heat the engine up and shift thru all gears including Reverse. Make sure A/C is off and transmission is in Park (automatic); or in Neutral for a Manual & release clutch. Then turn off engine, all accessories/lights (close driver's door) , etc.

Do KOEO test First. Post Code(s) here according to KOEO & KOER.
A helper can assist you by counting the codes. Some use their smart phones to record them.

BEWARE OF FAN, BELTS, PULLEYS, HOT HOSES, IGNITION HIGH TENSION WIRES, AND ENGINE COMPONENTS

Or ask local mom and dad parts stores if they will test it for you.
Or purchase a coder reader such as Equus 3145 Innova OBD 1 Code Reader for Ford EEC IV Engines at Walmart & most parts stores.

Here are two of code trouble shooting charts for Stalls:



Quick Test is the Diagnostic Trouble Codes Test
Idle Air Flow (ISC-BPA) AKA Idle Air Control Sensor (IAC)

Vacuum Leak; see my LeaK Test in post #11 @ https://www.fullsizebronco.com/threads/help-with-dtc-codes-and-idle.206824/
Excerpt:
"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."

●
Was speed control recall work, if equipped completed? If you still have concerns about Recalls, please contact the Ford Customer Relationship Center:
US: 800-392-3673 | CA: 800-565-3673
Note: 3673 spells "FORD" on phone keys
For the hearing- or speech-impaired: Please contact the Telecommunication Relay Service by dialing 71
"Summary: ON CERTAIN PICKUP TRUCKS, PASSENGER VEHICLES, SPORT UTILITY VEHICLES, AND MOTOR HOMES CHASSIS, THE SPEED CONTROL DEACTIVATION SWITCH MAY, UNDER CERTAIN CONDITIONS, LEAK INTERNALLY AND THEN OVERHEAT, SMOKE, OR BURN. THIS COULD RESULT IN AN UNDERHOOD FIRE."


1995 Bronco Dealer Brochure @ 1995 Ford Bronco

1995 Bronco Drivetrain, Powertrain Service Manual - Google Drive
&
1995 Bronco Chassis, Service Manual - Google Drive
To switch between folder list & grid views, click the button to the right of the "DOWNLOAD ALL" button in the upper right corner of the window) by HawkDriver

Haynes Red Manual for 80-95 Bronco & F Series @ Hanes guide 80-96 bko f series.pdf via BroncMom

Al

 

[Motech]

Wow, that's a lot of information you're getting here!

In everything mentioned above, I saw a mention of key-on-engine-running test. (KOER)
This would be a part of Ford's proprietary, On-Demand Self Testing protocols on all of their EEC IV (and later) models.

When the engine running self test is engaged with a scan tool capable of factory Ford testing, the operator will be directed to perform various inputs so that PCM can test certain items that it cannot test by itself. For instance, it will instruct us to press the brake pedal, turn the steering wheel a quarter turn, engage overdrive off buttons, and in some cases cruise control switches, etc., and then finally at end of self-test, it will request one single wide open throttle snap.

For brevity, we'll focus on the one portion of that test that probably applies to your problem: the steering wheel quarter turn.

That tests the power steering pressure sensor input. The computer uses that input to compensate for the exact issue you are experiencing. When you turn your wheel all the way left or right to the point of physical resistance, that resistance causes an increase in power steering pressure that creates a high pumping effort, which bogs the engine down due to increased PS pump pulley resistance. The computer compensates for this bogging by increasing your idle speed during these high pressure demands.

Now then, if that power steering pressure sensor value does not change when you turn the wheel during that self test, it will produce a diagnostic trouble code that is not reproduced in any other scenario.

In other words, if that sensor is failing, it will cause your engine to struggle and maybe even stall in tight parking lot in maneuvers when you're steering is turned all the way left or right. But it will not set a code that will be stored in memory, or generated during key on engine off testing, and it will never turn on your check engine light. It can only be generated in key on engine running testing.

So then, if you don't have the tool to perform Ford's on demand running test, what the heck do you do?

You need to pay somebody who has the enhanced Ford EEC IV software, or you just roll the dice and take a stab at the most likely culprits.

Absent a scan tool with Ford capabilities, what I would do in the scenario is:

• Replace the PS Pressure Sensor
,• Thoroughly clean the throttle body bores, especially around the throttle blades and their shafts using carburetor cleaner, bottle brushes and shop rags.
• Adjust minimum air rate the Harry Homeowner way as follows:
> Bring engine up to operating temperature
> While idling, disconnect the two wire Idle Air Bypass valve connector. This will cause the valve to close, and eliminate the computer control of engine idle.
If the engine stalls when you unplug it, adjust the throttle blade open a little bit more with the set ****** reconnect the idle air bypass valve, restart the engine and once it's idling smoothly again, disconnect the idle air bypass valve and repeat until you achieve around 500 RPM idle with control valve disconnected. Then reconnect everything and proceed to final step:
• Reset Keep-Alive Memory (KAM):
Disconnect your battery and leave it disconnected for 30 minutes. This will remove KAM power and erase all long-term adaptation memories.
Once reconnected, the computer will relearn it's idle strategies. This might cause some minor symptoms as it relearns, like poor idle control especially during cold start. This should all clear up after one or two cold starts, your engine should be running much better, and hopefully no longer stalling or labored idol controls during lock-to-lock steering maneuvers.

Hope this helps, and good luck to you.