Bronco Forum - Full Size Ford Bronco Forum banner
1 - 13 of 13 Posts

·
Registered
1990 EB, 5.0
Joined
·
533 Posts
Discussion Starter · #1 ·
It has been COLD lately! Over the past couple of weeks the truck will dies while moving slow and making turns. Starts right back up with no other issues.

7 months ago replaced the IAC with motorcraft, new plugs, wires, rotor and cap. No idle issues. Ran a can of seafoam through the brake booster line a few weeks ago to clean things out. Thoughts are the usual suspects TPS, FPR, MAP. I haven't replaced any of those. I've got 40psi on the rail. I also saw a write up suggesting flipping the battery backwards to avoid grounding out on the passenger fender, so I'll do that. Never had any engine issues prior. I suppose it could be time to replace the EEC as well.

Think I'll let it go awhile and see what happens before buying new parts. I'll try to pull codes when I get home and post.
 

·
Registered
Joined
·
1,412 Posts
I had a 6.0 diesel that apparently were prone to cut out on slow tight turns. Think it was the harness rubbing on the FICM. That same truck would give me ABS issues when cold (below 40). I’d add a harness look over to your troubleshooting.
 

·
Registered
Joined
·
8 Posts
does it do it when you're at a stop or do your rpms suddenly drop a few hundred rpms for a sec? my 89 also did that too. replaced virtually all sensors, vacuum lines, what have you. pulled the eec and sure enough there were some leaking capacitors and parts of the board looked a bit burnt. not saying you eec is bad, but definitely pull it out if you can and inspect it if you can.
 

·
Registered
1990 EB, 5.0
Joined
·
533 Posts
Discussion Starter · #4 ·
It happens while turning slowing, sometimes while coming to a stop light. Happened a few times in the past few weeks. But like I said COLD! If I pull the EEC I'll replace it. For the cost of $120 might as well.
 

·
Registered
'88 XLT. 2" lift, 3G, Saginaw Pump, Headers, High flow 3" cat, 3" exhaust, 6 litre tune, K&N
Joined
·
365 Posts
There is supposed to be a sensor on the power steering pressure hose that is supposed to bump up the idle during hard steering. If that sensor is bad or unhooked, that could be it.
 
  • Like
Reactions: packagerjr

·
Registered
1990 EB, 5.0
Joined
·
533 Posts
Discussion Starter · #6 ·
Nope. Sensor is plugged in.
 

·
Registered
2014 Ford Explorer Sport
Joined
·
1,800 Posts
Run the KOEO tests and Stored Code display to see if the Power Steering Switch (PSP) is working. I also suggest to pull off the IAC, inspect and clean it. Use a new gasket when re-installing.
 

·
Super Moderator
Joined
·
29,855 Posts
Yo Siggy89,
As rla2005 advised;
Try a Self Test for Diagnostic Trouble Codes (DTC)s by my pal, BroncoJoe19 @ Code Reader
EEC AKA PCM, computer 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 EEC will tell you what it found out by testing your sensors, and also any stored information it saved from anything that went wrong during the last 40 trips.
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 store
The Power Steering Pressure Switch signals the EEC Module when power steering pressure exceeds 350 psi. The engine then increases idle speed to compensate for the additional load. It appears the switch was deleted from the '94 model year. It only shows up in the diagrams until '93. the switch is directly above the steering box."
 

·
Registered
1990 EB, 5.0
Joined
·
533 Posts
Discussion Starter · #9 ·
Just did the KOEO test. Got a few codes
21- engine temp cold (duh)
24- air temp out of range (duh)
63- throttle position sensor below voltage *** Bingo!

I'll run a KOER test as well to see, but I'm hoping that's it. I also sprayed some QD electric cleaner on the power steering sensor cause it looked pretty dirty.
 

·
Super Moderator
Joined
·
29,855 Posts
Yo Siggy,
21- engine temp cold (duh)
The ECT is a Thermistor, (or Thermal Resistor), which reduces VREF Voltage to the SIG RTN as it gets warmer. One wire is VREF and the other wire is SIG RTN (Signal Return). Failure in either the circuit or temperature sensor will show a DTC 21, 51, 61 or 116, 117, 118.
ECT Reference Voltage Testing
  • Start by checking the connector to ensure that the pins are making good contact.
  • Check the reference voltage at the unplugged connector with the key on, engine off.
  • Should be approximately 5.0v.
ECT Sensor Voltage Testing
  • Before warming the engine, test the SIG RTN Voltage by back probing the plugged in harness connector with KOEO & KOER and record the voltage.
  • Should be approximately 3.7 v cold.
The ECT is a Thermistor, (or Thermal Resistor), which reduces VREF Voltage to the SIG RTN as it gets warmer. One wire is VREF and the other wire is SIG RTN (Signal Return). Failure in either the circuit or temperature sensor will show a DTC 21, 51, 61 or 116, 117, 118.


ECT Reference Voltage Testing
  • Start by checking the connector to ensure that the pins are making good contact.

  • Check the reference voltage at the unplugged connector with the key on, engine off.

  • Should be approximately 5.0v.


ECT Sensor Voltage Testing
  • Before warming the engine, test the SIG RTN Voltage by back probing the plugged in harness connector with KOEO & KOER and record the voltage.

  • Should be approximately 3.7v cold.

  • Then at normal operating temperature, back probe again.

  • Should be approximately .5v warm.


ECT Sensor Resistance Testing
  • Unplug the harness connector.
  • Then, check the resistance of the sensor cold. Should be between 40,500 to 58,750 ohms.
  • Plug in the harness connector and warm up the engine to normal operating temperature.
  • Then, unplug and check the resistance of the sensor hot. Should be 1,840 to 3,600 ohms.

  • Then at normal operating temperature, back probe again.
  • Should be approximately .5v warm.
ECT Sensor Resistance Testing
  • Unplug the harness connector.
  • Then, check the resistance of the sensor cold. Should be between 40,500 to 58,750 ohms.
  • Plug in the harness connector and warm up the engine to normal operating temperature.
  • Then, unplug and check the resistance of the sensor hot. Should be 1,840 to 3,600 ohms.


24- air temp out of range (duh)
Rectangle Product Font Screenshot Parallel

Rectangle Font Line Screenshot Material property

Rectangle Font Material property Screenshot Parallel


63- throttle position sensor below voltage *** Bingo!
53 KOEO TPS circuit above maximum 4.5 volts.
CM TPS circuit has intermittently failed above maximum 4.5 volts.
Test @ Fuel Injection Technical Library » Throttle Position Sensor (TPS) by Ryan
&
63 KOEO TPS circuit below minimum 0.6 volts.
TPS circuit has intermittently failed below minimum 0.6 volts.
Rectangle Font Material property Parallel Diagram
 

·
Registered
1990 EB, 5.0
Joined
·
533 Posts
Discussion Starter · #11 ·
Thanks for that. I unplugged all the connections and cleaned them up a little with the QD spray. Also cleaned up the ground wire by the EEC and reattached, plus disconnected and cleaned up the connection at the IAC. Didn't flip the battery because I don't think that's the issue. Took it out for a drive and didn't have any issues. I still have a new motorcraft TPS arriving next week, but for now things seem to be good.
 

·
Registered
2014 Ford Explorer Sport
Joined
·
1,800 Posts
Be sure to run the KOER tests to see if the Power Steering Pressure Switch (PSP) gets flagged as bad. You may have more than one issue.
 

·
Registered
1990 EB, 5.0
Joined
·
533 Posts
Discussion Starter · #13 ·
Be sure to run the KOER tests to see if the Power Steering Pressure Switch (PSP) gets flagged as bad. You may have more than one issue.
Installed new TPS and replaced the gasket for the IAC. No issues, think it is solved. Cleaned up the QD for the PS as well.
 
  • Like
Reactions: rla2005
1 - 13 of 13 Posts
Top