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1987 - 1996 F150 & Larger F-Series Trucks 1987 - 1996 Ford F-150, F-250, F-350 and larger pickups - including the 1997 heavy-duty F250/F350+ trucks

~2,000 RPM Idle, KOER 63c and 96c Codes

 
  #1  
Old 04-18-2019, 09:13 PM
treeguy39040
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~2,000 RPM Idle, KOER 63c and 96c Codes





My 1988 F150 "farm truck" (XLT Lariat, straight 6, 300 CID, 5 speed manual, standard cab, longbed, dual tanks, 34,357.9 on odometer that has flipped over three or four times--not sure which, 2nd alternator, 2nd OEM transmission, replaced water pump twice but no major engine work...) has developed an extremely fast ~2,000 RPM idle at start up and all times, even when engine is warmed up.

Originally, it had an ~1,500 RPM idle and was generating 34c, 51c and 51o codes, so I replaced the following (See photos.):
  1. Idle Air Contol Valve (which would not move),
  2. Coolant Temperature Sensor,
  3. MAP Sensor,
  4. EGR Position Sensor,
  5. EGR Vacuum Solenoid and
  6. EGR Valve

Then the ~1,500 RPM idle increased to ~2,000 RPM! 🙄😮 And now it generates the following codes:
  1. 11c (KOEO "pass code"),
  2. 10 ("separation code"),
  3. 63c {Throttle Position (TP) circuit fault, below minimum voltage} and
  4. 96c (Fuel pump secondary circuit fault / high speed fuel pump relay open)

What should I test and/or renew next?
 
  #2  
Old 04-19-2019, 06:45 AM
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The 96 code can be from testing the fuel system.
You may have a bad new Idle Air Control Valve.
The TPS may be out of adjustment as it passed its electrical test in the KOEO test.
 
  #3  
Old 04-19-2019, 10:46 AM
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Did you run the KOER Self-Test ?

Check the output of the TPS; Fuel Injection Technical Library Throttle Position Sensor (TPS)

Has your Throttle Stop Screw been tampered with ?

Disconnect your new Air Bypass Valve to see if it lowers the Idle.
 
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Old 04-19-2019, 11:51 AM
treeguy39040
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Originally Posted by vjsimone View Post
Did you run the KOER Self-Test ?
I reread the five (5) KOER pages (pp. 32-36) and realized I must have done it wrong.

I thought because 11 then 10 originally displayed it meant all the KOEO tests passed, and it was "separating" (...or whatever??) and then performing KOER tests, however, I do not remember ever seeing any "R" pop up ('A small "R" is shown...indicate that the code...is a KOER Self Test Fault Code.") OR any 6 for the "cylinder ID code identifies the number of cylinders of the vehicle that is under test."

Therefore, I assume it was still in Key On Engine OFF mode even though the engine was warmed up AND running (i.e., not KOER mode)?

Originally Posted by vjsimone View Post
Has your Throttle Stop Screw been tampered with
I haven't touched it but have been "looking" for that animal, with no success, ever since I got the truck (I am the 2nd owner; bought it in "'94ish" @ ~34k mi., as I recall.). Lol

I just assumed the Throttle Positioner Sensor (TPS See photo.) and the Idle Air Control Valve must replace any simple "old-school" analog idle stop screw? Please educate me. 🤔
 
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Old 04-19-2019, 01:15 PM
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Unhook Stuff Tests

Originally Posted by vjsimone View Post
Disconnect your new Air Bypass Valve to see if it lowers the Idle.
Okay, I did various unhooking tests of the new Idle Air Contol Valve and original Throttle Position Sensor (TPS...not new, but with the help of a Phillips head on a " drive ratchet AND WD40, removed and reinstalled with dielectric grease applied to connector terminals). See video. Here is a summary of the results:
  1. Unhooking the Idle Air Contol Valve did not decrease idle.
  2. Unhooking the TPS (...with the Idle Air Contol Valve also unhooked) did not decrease idle.
  3. Re-hooking back up the Idle Air Contol Valve (...without the TPS hooked up) increased idle.
 
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Old 04-19-2019, 01:29 PM
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No *.mp4??


Hmmmm, guess ford-trucks.com does not allow mp4 video format? Well, hopefully y'all can understand the mp3 audio conversion! 😉
 
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Old 04-19-2019, 05:16 PM
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All I could hear was some squeaking from your file.

The Throttle Plate Stop Screw is to keep the Throttle Plates from sticking in the Throttle Body. It is not for adjusting the Idle, but affects the Idle and output of the TPS when turned unnecessarily.

You will need to check the output voltage, etc, of the TPS, see post #3.

The self-test can be challenging in the beginning, it is easier with a helper, someone to watch the reader and someone on the accelerator.
Have something to write on, a small note book is handy for follow-on troubleshooting.
Warm engine up to operating temperature before each self-test (KOEO & KOER).
For the KOER self-test increase rpm to 2000 just prior to starting Self-test.
When you see the 10 displayed on your reader after the # of cylinders are displayed, floor the accelerator, hold it, 1001, ok let up.
Write all the codes down in the order they display. Pay attention to the small letters (O,C,R) in the top right corner of the reader, write these down with the Codes.
You will hear the engine Cough, when the testing sequence is complete, or what the book says.

You will have to check for vacuum leaks.
 
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Old 04-19-2019, 07:18 PM
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We had nasty tornadic weather yesterday and more rain today--basically, I call Mississippi Winters and Springs "Monsoon Season!" Lol Tomorrow and Easter Sunday is supposed to be sunny, so I plan to tackle the KOER self-test then since this is all "shade tree" work. 😉

Originally Posted by vjsimone View Post
All I could hear was some squeaking from your file.
No problem, I had summarized the results (See "Unhooking Stuff Tests" reply.)...

Originally Posted by treeguy39040 View Post
Here is a summary of the results:
  1. Unhooking the Idle Air Contol Valve did not decrease idle.
  2. Unhooking the TPS (...with the Idle Air Contol Valve also unhooked) did not decrease idle.
  3. Re-hooking back up the Idle Air Contol Valve (...without the TPS hooked up) increased idle.
The self-test can be challenging in the beginning, it is easier with a helper, someone to watch the reader and someone on the accelerator.
Your tips are especially welcome, considering the overly wordy manual--it keeps repeating trivial points and neglects to explain most germane subjects! Lol

Unfortunately, I have no helper, but fortunately I invested in the 6 ft. long code reader extension cord, which allows me to sit in the driver's seat to watch the reader with notepad and pen.

You will have to check for vacuum leaks.
I plan to completely replace all vacuum hoses because they all are all visibly checked and cracked. Hopefully no plastic fittings break in the process! Lol
 
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Old 04-19-2019, 07:42 PM
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For VJ



 
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Old 04-19-2019, 10:46 PM
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Sandy posted a photo of the Throttle Plate Stop Screw.

Thanks Sandy
 
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Old 04-20-2019, 12:08 AM
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Special Coating on Throttle Plate and ????



Originally Posted by vjsimone View Post
Sandy posted a photo of the Throttle Stop Screw.

Thanks Sandy
I second the thanks, Sandy, but Kitty and I are both curious what the final word is on that warning label (2nd photo), and zoom in on the 1st photo to see why I never could find the elusive HARD STOP SCREW!! Lol

I have had this high idle problem ever since I bought the truck second hand, although it was originally a less exasperating 1,200 RPM.

I first took it to a Ford Dealer and spoke with the Service Manager. He suggested I buy some throttle body cleaner, spray the inside of the throttle body liberally, scrub the inside with an old toothbrush to loosen all the varnish, start the engine then again spray inside the throttle body until it kills the engine.

I followed his instructions (Hmmmm, and it looks like he never bothered to read one of the warning labels, which was gone on my truck when I bought it.), the idle went down to ~1,000 RPM then basically forgot about it since Al Gore hadn't invented The Internet yet! Lol 😁🤣
 
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Old 04-20-2019, 04:07 AM
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Your Throttle Plates should be all the way closed at Idle. If you held your TB up to the light, you would not see much light through it.

also, look at your plates to see if there are any holes drilled in the plates.

See post #3, measure the output of the TPS.
 
  #13  
Old 04-20-2019, 06:25 AM
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Have you checked for vacuum leaks? Are all the original plastic lines still on there? Double check brake booster by capping that line .
 
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Old 04-20-2019, 11:56 AM
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New TPS & Vacuum Lines Ordered

Originally Posted by vjsimone View Post
Your Throttle Plates should be all the way closed at Idle. If you held your TB up to the light, you would not see much light through it.

also, look at your plates to see if there are any holes drilled in the plates.

See post #3, measure the output of the TPS.
Originally Posted by KubotaOrange76 View Post
Have you checked for vacuum leaks? Are all the original plastic lines still on there? Double check brake booster by capping that line .
The throttle plates appear closed at engine off and idle, and I'm reluctant to remove the throttle body to hold it "up to the light" for fear of broken bolts (...as it appears someone previously snapped off the throttle hard stop screw).

Since I don't really understand how every vacuum line functions, I'm really at a loss how to methodically check for leaks besides doing visual inspections. All the lines are original, and as stated previously, have seen much better days. I do not hear any obvious hissing, although it's virtually impossible to tell for sure at 2,000 RPM!!

I have ordered a new TPS (...assuming it will fail the smooth voltage progression line test) and new vacuum lines, but the ship-to-home order won't arrive until "Est. Delivery: Apr 26-30."
 

Last edited by treeguy39040; 04-20-2019 at 11:57 AM. Reason: Typo
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Old 04-20-2019, 12:47 PM
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Originally Posted by treeguy39040 View Post
.as it appears someone previously snapped off the throttle hard stop screw.
Nope, that is the way it comes from the factory.
I have seen a few that way.

Here is my old 88 TB stop screw:


/
 

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