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#1 TheBus

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Posted 29 August 2011 - 02:23 PM

So the Bronco is running ok after replacing the alternator except for idling. The problem now is the fast idle isn't kicking in when I start her up and the engine is cold. It would usually idle fairly high then tone down with no idle issues at all. It stalled on me for the first time today coming home from work idling in traffic. I just got her back on the road now she's not idle correctly...

The idle is also "hunting" when it starts to warm up (some times cold) and it never used to do that. It's putting a strain on the electrics when it surges up/down. I can watch the voltage drop as the idle drops, then the gauge goes back to normal voltage as the loping idle hits its high point. Does the EFI 302ci have a fast idle vavle or is it just handled by the idle air control valve? Any suggestions on where to start?
87 Bronco XLT 302

#2 Rons beast

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Posted 29 August 2011 - 03:22 PM

my 96 302 had to "Learn" new settings when the idle speed control was replaced. It had no fast idle valve, and was "hunting" too. It may be the same with your situation.
I had to drive about 5 miles for the reset.

Edited by Rons beast, 29 August 2011 - 03:24 PM.

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#3 TheBus

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Posted 29 August 2011 - 04:42 PM

That's a good point because the battery had been disconnected for a couple weeks. I'm sure the ECU had lost all of its stored data. However, I have driven it approximately 30 miles. You'd think the computer would have learned something from its sensors in that amount of time...
87 Bronco XLT 302

#4 Rons beast

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Posted 29 August 2011 - 07:19 PM

If you just changed the alternator, double check that you didn't knock off a vacuum line. That would surely cause a hunting idle and stalling.
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#5 miesk5

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Posted 05 September 2011 - 03:50 AM

yo,

Have you done a Self Test for Codes, by our Brother-in-Grease and other Fluids, BroncoJoe19?
http://broncozone.co..._mode__threaded

heat the engine up; idle until temp gauge is in normal range you usually see
and when it warms up; shift thru all gears incl Reverse anyway.

Then turn off all accessories/lights, etc.

Make sure A/C is off and transmission is in Park (automatic)

Do Key On Engine Off (KOEO) portion first.

The engine temperature must be greater than 50°F (10°C) to pass the KOEO Self-Test and greater than 180°F (82°C) to pass the KOER Self-Test.

And Post em here according to
KOEO
&
KOER



A Possibilty, but ck for codes First
Idle Air Control (IAC) Sludge; Poor Idle TSB 91-25-07 for 85-92 Bronco & F Series & many others; "...Hard cold starts, hesitation and stalls on initial start-up or during idle or decel may be caused by sludge in the throttle body and/or idle by-pass valve.. READ MUCH MORE @ http://www.supermoto...ry/media/724437
by Ford via Steve83
Here it is in case SM goes down again today;
TSB 91-25-07 IAC Sludge; Poor Idle
Publication Date: DECEMBER 13, 1991
tsb912507iacsludge.jpg
IF THE IMAGE ABOVE IS TOO SMALL TO READ, CLICK IT

FORD: 1983-87 EXP
1983-91 ESCORT
1984-90 MUSTANG, THUNDERBIRD
1986-90 TAURUS
1986-91 CROWN VICTORIA
1988-90 TEMPO
LINCOLN-MERCURY: 1983-85 LN7
1983-87 LYNX
1984-88 CAPRI
1984-90 COUGAR
1986-90 CONTINENTAL, MARK VII, SABLE
1986-91 GRAND MARQUIS, TOWN CAR
1988-90 TOPAZ
1991 TRACER
LIGHT TRUCK: 1985-90 BRONCO II, BRONCO
1985-91 ECONOLINE, F-150-350 SERIES
1985-92 RANGER
1986-91 AEROSTAR
1991 EXPLORER

ISSUE: Hard cold starts, hesitation and stalls on initial start-up or during idle or decel may be caused by sludge in the throttle body and/or idle by-pass valve. Sludge deposits or oil film on the throttle body bore and plate or the idle air by-pass valve may cause one or more of the following conditions.
Hard Cold Start
Stall On Initial Start-Up
Stall During Idle
Stall During Decel
Rough Idle
Rolling Idle
Hesitation During Acceleration

ACTION: A new idle air by-pass service kit (F2PZ-9F939-A) is now available for service use to correct sludge contamination concerns of the throttle bore and plate only. It eliminates the need to clean the majority of past model throttle body applications. Cleaning is not required on sludge tolerant throttle body designs released for 1991 and newer model years.

Install an idle air by-pass service kit (F2PZ-9F939-A) as applicable to provide a permanent correction for symptoms caused by throttle body sludge deposits. Refer to the instruction sheet included in the kit for installation details. Refer to Figure 1 for a specific application list of EFI (port fuel Injection) engines involved in this TSB article.

The idle air by-pass service kit (F2PZ-9F939-A) includes the following items.

One (1) Idle Adjust Spacer
Two (2) Gaskets
Two (2) Attaching Bolts
One (1) "Attention" Sticker
One (1) Instruction Sheet
Refer to the figure for the kit's components.
NOTE: EFFECTIVE WITH THIS TSB, THROTTLE BODY CLEANING IS NO LONGER COVERED UNDER 5/50 EMISSIONS WARRANTY, UNLESS AS SPECIFIED IN THE FOLLOWING APPLICATION CHARTS. FAILURE TO FOLLOW THE CORRECT PROCEDURE MAY RESULT IN THE CLAIM BEING DISALLOWED.
The idle air adjust spacer incorporates sludge tolerant design features that eliminate throttle body sludge related conditions. Once installed, throttle body cleaning is not allowed and periodic adjustment of the throttle body is not required.

CHECKS TO MAKE PRIOR TO SERVICE KIT INSTALLATION
Confirm that the following items are not causing the idle quality concern before proceeding with the service kit installation.

Contamination within the idle air by-pass solenoid
Lack of fuel system control (excessively rich or lean)
Ignition timing change
Incorrect or malfunctioning EGR system
Incorrect or malfunctioning cooling system
Vacuum leaks (air intake manifold, vacuum hoses, vacuum reservoirs, power brake booster where applicable).
EEC diagnostics have been performed and vehicle malfunction indicated service output codes have been resolved and cleared.
If any of the areas listed above are found to be at fault, correct them before proceeding with the service kit installation.

IDLE SPEED ADJUSTMENT
WARNING: BEFORE PROCEEDING WITH THE IDLE SPEED ADJUSTMENT, VERIFY THAT THE FOLLOWING ITEMS ARE TAKEN CARE OF PROPERLY. The transmission is in PARK or Neutral.
The parking brake is applied.
The wheels are properly blocked.
The engine is at operating temperature.
The heater. A/C, cooling fan and other accessories are OFF.
The EFI throttle body idle speed adjustment procedures for the various model year passenger cars and light trucks are outlined in step-by-step procedures. Select the appropriate procedure for the vehicle involved and adjust the throttle body idle RPM accordingly, after service kit installation.

THROTTLE BODY AND IDLE AIR BY-PASS SOLENOID SERVICE PROCEDURE
Detailed application charts for throttle body and idle air by-pass solenoid service procedures by engine VIN #/engine displacement/vehicle application and model year are shown. Refer to these charts to see if the service kit is to be installed and which service cleaning procedure, if any, is to be used.

SERVICE CLEANING PROCEDURES
The following items should be noted prior to beginning the service cleaning procedure.

Confirm that the correct service cleaning procedure is identified in the Application Charts, Figures 6-11, for the vehicle/engine combination being serviced.
Do not clean throttle bodies identified to accept service kit (F2PZ-9F939-A), IDLE AIR ADJUST SPACER.
Use a 1" (25.4mm) to 1 1/2" (38.1mm) wire stemmed horse hair or nylon bottle cleaner type brush.
Use rubber gloves and eye protection.
Do not clean throttle bodies identified with a yellow/black "ATTENTION" label.
Do not clean "Black" plastic air by-pass valves. Refer to TSB 89-13-8 for service details.
Do not run vehicles with air flow meters when the air duct is removed.
Do not use carburetor cleaner as a cleaning solvent. Use Carburetor Tune-up Cleaner (D9AZ-19579-AA).

PROCEDURE #1
THROTTLE BODY AND IDLE AIR BY-PASS VALVE CLEANING
CAUTION: DO NOT RUN VEHICLES EQUIPPED WITH AIR FLOW METERS DURING THE CLEANING PROCEDURE. IF THERE IS A YELLOW/BLACK "ATTENTION" LABEL ON THE THROTTLE BODY ADVISING NOT TO CLEAN, OR IF THE VEHICLE IS IDENTIFIED AS ACCEPTING SERVICE KIT (F2PZ-9F939-A), USE PROCEDURE #2 FOR IDLE AIR BY-PASS VALVE CLEANING ONLY.
Plug the actuator into the connector in the Rotunda Cleaner/Tester, Tool 113-00009.
Remove the air duct to the throttle body inlet.
Disconnect the idle air by-pass valve signal lead.
Attach the actuator harness plug to the idle air by-pass valve.
Start the actuator and then start the engine. Do not start engines that have air flow meters.
Spray just enough Carburetor Tune-up Cleaner (D9AZ-19579-AA) into the throttle bore to wet the bore and throttle plate.
Spray the Carburetor Tune-up Cleaner for about five (5) seconds into the idle air by-pass valve inlet passage while the actuator is operating.
Stop the engine and actuator. Let everything soak for fifteen (15) minutes.
After a fifteen (15) minute soak, saturate the cleaning brush with solvent and scrub between the throttle body bore and plate while holding the throttle wide open.
NOTE: IT IS NECESSARY TO APPLY SOME PRESSURE ON THE BRUSH WHILE SCRUBBING.
Repeat saturating the brush and scrubbing for one (1) to two (2) minutes, making sure to reach into the corners where the throttle shaft meets the bore wall.
Start the actuator and the start the engine. Do not start engines that have air flow meters.
Spray Carburetor Tune-up Cleaner into the throttle bore for up to one (1) minute to wash away residue. Do not spray for longer than six (6) continuous seconds on engines that have air flow meters and are not running.
Spray Carburetor Tune-up Cleaner into the idle by-pass valve passage leading to the inlet of the valve for up to one (1) minute. Do not spray for longer than six (6) continuous seconds on engines that have air flow meters and are not running.
Stop actuator and stop engine, if running.
NOTE: MAKE SURE THE THROTTLE PLATES OPERATE FREELY AND CLOSE PROPERLY.
Reinstall the air duct.
Start and run the engine for about one (1) minute to dry out the solvent residue.
Operate the actuator to make sure the solvent is purged from the idle by-pass valve.
Disconnect the actuator from the idle air by-pass valve.
Reattach the control signal lead to the air by-pass valve.
Check engine for normal operation. It may be necessary to reset the idle speed due to a previous adjustment for an idle concern. (Refer to the respective Powertrain/Emissions Diagnosis Service Manual, Throttle Body Section, for idle speed adjust procedure.)

Alternate Cleaning Procedure for Hitachi IACs
NOTE: Method to be used only when the Rotunda Fuel Injector Tester/Cleaner 113-00001 and Air Bypass Valve Actuator 113-00009 or equivalent for the recommended method are not available.

1. Remove the idle air control valve from the throttle body.
2. Remove the electrical solenoid assembly from the mechanical portion of the idle air control valve by removing the two screws, then sliding the mechanical portion away from the solenoid.
3. CAUTION: Do not exceed three minutes soak time, and do not use choke cleaner as an internal O-ring may begin to deteriorate. Soak the mechanical portion in Carburetor Tune-Up Cleaner D9AZ-19579-BA meeting Ford specification ESR-M14P9-A or equivalent for two to three minutes maximum.
4. With the mechanical portion completely submerged, shake in all directions: up, down, right and left. Then push in on the rod that mates with the solenoid assembly, and again shake in all directions with the unit submerged and the rod held in as far as possible.
5. Remove the unit from the cleaning fluid and dry out thoroughly using shop air.

PROCEDURE #2
IDLE AIR BY-PASS VALVE CLEANING ONLY
CAUTION: THIS CLEANING PROCEDURE MAY BE USED WITH SLUDGE TOLERANT THROTTLE BODIES WHICH ARE IDENTIFIED WITH A YELLOW/BLACK "ATTENTION" LABEL AND THOSE USING SERVICE KIT (F2PZ-9F939-A). NO ATTEMPT SHOULD BE MADE TO CLEAN THROTTLE BODY BORE/PLATE AREA BY DIRECT SPRAYING OR SCRUBBING. DO NOT RUN VEHICLES WITH AIR FLOW METERS DURING CLEANING PROCEDURE.
Plug the actuator into the connector in the Rotunda Air By-Pass Valve Adapter 113-00009, or equivalent.
Remove the air duct to the throttle body inlet.
Disconnect the idle air by-pass valve signal lead.
Attach the actuator harness plug to the idle air by-pass valve.
Start the actuator and then start the engine.
NOTE: DO NOT START ENGINES THAT HAVE AIR FLOW METERS.
Spray the Carburetor Tune-up Cleaner for about five (5) seconds into the idle air by-pass valve inlet passage while the actuator is operating.
CAUTION: AVOID DIRECT SPRAYING ON THROTTLE PLATE/BORE AREA
Stop the engine and actuator. Let everything soak for fifteen (15) minutes.
Start the actuator and the start the engine.
CAUTION: DO NOT START ENGINES THAT HAVE AIR FLOW METERS.
Spray Carburetor Tune-up Cleaner into the throttle bore for up to one (1) minute.
CAUTION: DO NOT SPRAY FOR LONGER THAN SIX (6) CONTINUOUS SECONDS ON ENGINES THAT HAVE AIR FLOW METERS AND ARE NOT RUNNING.
Stop actuator and stop engine if running.
Reinstall the air duct.
Start and run the engine for about one (1) minute to dry out the solvent residue.
Operate the actuator to make sure the solvent is purged from the idle by-pass valve.
Disconnect the actuator from the idle air by-pass valve.
Reattach the control signal lead to the air by-pass valve.
Check engine for normal operation.
NOTE: IT SHOULD NOT BE NECESSARY TO RESET THE IDLE SPEED SINCE ONLY THE IDLE AIR BY-PASS VALVE WAS SERVICED IN THIS PROCEDURE

Alternate Cleaning Procedure for Hitachi IACs
NOTE: Method to be used only when the Rotunda Fuel Injector Tester/Cleaner 113-00001 and Air Bypass Valve Actuator 113-00009 or equivalent for the recommended method are not available.

1. Remove the idle air control valve from the throttle body.
2. Remove the electrical solenoid assembly from the mechanical portion of the idle air control valve by removing the two screws, then sliding the mechanical portion away from the solenoid.
3. CAUTION: Do not exceed three minutes soak time, and do not use choke cleaner as an internal O-ring may begin to deteriorate. Soak the mechanical portion in Carburetor Tune-Up Cleaner D9AZ-19579-BA meeting Ford specification ESR-M14P9-A or equivalent for two to three minutes maximum.
4. With the mechanical portion completely submerged, shake in all directions: up, down, right and left. Then push in on the rod that mates with the solenoid assembly, and again shake in all directions with the unit submerged and the rod held in as far as possible.
5. Remove the unit from the cleaning fluid and dry out thoroughly using shop air.

WARRANTY COVERAGE
Throttle bodies and idle air by-pass valves on all EFI (Port Fuel Injection) engines through the 1992 model year that can be cleaned (as identified in the application charts) are covered under 5/50 Emissions Warranty Coverage.

For those throttle bodies identified as having sludge tolerant designs or using service kit (F2PZ-9F939-A) where cleaning is not allowed per the application charts, the warranty claims for cleaning will not be reimbursed even within the 12/12 warranty coverage period. Cleaning is not allowed. Service kit installation (single time) is covered under 5/50 emission warranty.

LABOR STANDARDS OPERATIONS
The labor operations shown in the following Operation/Description/Time columns are identified by procedure number and vehicle line. Specific engines for various vehicles are identified in the sludge cleaning procedure application charts. The throttle body cleaning operations with combinations and the air by-pass valve cleaning combinations will appear in future Labor Manuals under the following operation numbers.

9926 B - Throttle body and idle air by-pass valve cleaning
9926 B2 - Adjust idle speed
9715 A - Air by-pass valve cleaning only
9715 A1 - Adjust idle speed

PART NUMBER PART NAME
F2PZ-9F939-A Idle Air By-pass Service Kit
D9AZ-19579-AA Carburetor Tune-Up Cleaner

OTHER APPLICABLE ARTICLES: 89-13-8
SUPERSEDES: 88-24-5, 88-24-6, 89-16-5, 91-10-9, 91-7-4
WARRANTY STATUS: Eligible Under Warranty Coverage As Stated In The Text Of This Article

OPERATION DESCRIPTION TIME
912507A Idle Air By-Pass Valve Cleaning - 1983-85 Escort, EXP, LN7, LYNX 1.6L EFI. 0.5 Hr.
912507B Idle Air By-Pass Valve Cleaning - 1986-91 Escort 1.9L EFI, 1986/87 EXP, Lynx 1.9L EFI, 1991 Tracer 1.9L EFI. 0.5 Hr.
912507C Idle Air By Pass Valve Cleaning - 1984-87 Mustang 2.3L T/C, 1986/87 Capri, Cougar 2.3L T/C, 1984-88 T-Bird 2.3L T/C, 1987/92 Mustang 2.3L EFI. 0.5 Hr.
912507D Idle By-Pass Valve Cleaning - 1988-91 Tempo, Topaz 2.3L HSC, 1985-92 Ranger 2.3L EFI. 0.6 Hr.
912507E Idle Air By-Pass Valve Cleaning - 1986/87 Aerostar 2.3L EFI, 1985 Bronco II 2.3L EFI. 0.7 Hr.
912507F Idle Air By-Pass Valve Cleaning - 1986-90 Bronco II 2.9L EFI, 1986-92 Ranger 2.9L EFI. 0.7 Hr.
912507G Idle Air By-Pass Valve Cleaning - 1991/92 Probe 3.0L EFI, 1986-91 Taurus 3.0L EFI, 1987-91 Sable 3.0L EFI. 0.6 Hr.
912507H Idle Air By-Pass Valve Cleaning - 1986-91 Aerostar 3.0L EFI, 1991 Ranger 3.0L EFI. 0.7 Hr.
912507I Idle Air By-Pass Valve Cleaning - 1988 Continental, Cougar, Taurus, T-Bird, Sable 3.8L EFI. 1988 Cougar, T-Bird 3.8L S/C. 0.6 Hr.
912507J Idle Air By-Pass Valve Cleaning - 1990-92 Aerostar 4.0L EFI, 1990 Bronco II 4.0L EFI, 1991/92 Explorer 4.0L EFI, 1990-92 Ranger 4.0L EFI. 0.7 Hr.
912507K Idle Air By-Pass Valve Cleaning - 1987-92 Bronco 4.9L EFI, 1987-92 F-Series 4.9L EFI, 1987/90 Econoline (Without Rear Heater) 4.9L EFI, 1991/92 Econoline (All) 4.9L EFI. 0.7 Hr.
912507L Idle Air By-Pass Valve Cleaning - 1986-88 Cougar, T-Bird 5.0L EFI, 1986-87 Continental, Mark VII 5.0L EFI, 1986/91 Crn - Victoria, Grn - Marquis 5.0L EFI, 1986-92 Mark VII 5.0L HO, 1982-92 Mustang 5.0L HO. 0.6 Hr.
912507M Idle Air By-Pass Valve Cleaning - 1985-92 Bronco, E-Series, F-Series 5.0L EFI. 0.7 Hr.
912507N Idle Air By-Pass Valve Cleaning - 1988-90 Bronco, F-Series 5.8L. 1991 Econo, F-Series, Bronco 5.8L (Do not Clean Solenoid, Calib; 1-64E-R10,1-64H-R10,1-64J-R10,1-64K-R10,1-64M-R10,1-64P-R10,1-64R-R10,1-75A-R00,1-76A-R00,1-76B-R00,1-76C-R00) 0.7
912507O Idle Air By-Pass Valve Cleaning - 1991/92 F And B Series, 7.0L EFI. 0.7 Hr.
912507P Idle Air By-Pass Valve Cleaning - 1987-92 E-Series, F-Series 7.5L EFI. 0.7 Hr.
912507Q Throttle Body And Idle Air By-Pass Valve Cleaning - 1989/90 Probe 3.0L EFI. 0.9 Hr.
912507R Throttle Body And Idle Air By-Pass Valve Cleaning - 1987-90 Econoline (With Rear Heat) 4.9L EFI. 0.8 Hr.
912507S Throttle Body And Idle Air By-Pass Valve Cleaning - 1988-90 Econoline 5.8L EFI. 0.9 Hr.
912507T Service Kit Install - All Cars And Light Trucks (Except Aerostar And Econoline) - Refer To The Service Procedure Application Charts, For Vehicle Application. 1.0 Hr.
912507U Service Kit Install - Aerostar, Econoline - Refer To Service Procedure Application Charts - For Vehicle Application. 1.2 Hr.


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#6 Bronco Kid!

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Posted 16 September 2011 - 06:56 PM

well crap miesk5 is so hard to follow up.. i had a good train of thought till i read his post it definetly blew my comment of check your idle postioning sensor away

#7 nelbur

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Posted 17 September 2011 - 08:01 AM

I checked on the Idle Air Service Kit that Miesk5 mentioned. Ford has them for $89, and an outfit named TOMCO has "one" for $64. It is just a spacer with set screws that allow air to bypass the IAC. I'm too cheap to pay that kind of money to solve my stall on hot start problem. I've grown used to catching it with a bit of accelerator when it starts up. I think I will try cutting away some of the gasket between the air holes, to allow air to bypass the IAC. It could be adjusted by trial and error by cutting away more gasket, and the gasket could even be doubled up if more bypass is needed. Anyone know why this cheapskate fix would not work?
'86 302 EFI

#8 bobstrat

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Posted 24 September 2011 - 06:44 AM

Anyone know why this cheapskate fix would not work?


why not disconnect the iac at the plug and see if it makes a difference?
you could be barking up the wrong tree from the start.

have you tried pulling codes? this is the step everyone skips, though often the most helpful.
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#9 nelbur

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Posted 24 September 2011 - 03:29 PM

Well, my idle hunting problem has been around for about 25 years. Under warranty I would just take the truck back and say, "It's idling like crap. Fix it!" And they would clean everything, and it would be fine for a few months. I learned to live with it after the warranty ran out. It wasn't until miesk5 mentioned the kit that I understood what was going on. I have never seen an idle related code. I'll try the cut away gasket as soon as I get the time. Thanks to miesk5 for the info on the kit idle fix.
'86 302 EFI

#10 miesk5

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Posted 25 September 2011 - 03:29 AM

I checked on the Idle Air Service Kit that Miesk5 mentioned. Ford has them for $89, and an outfit named TOMCO has "one" for $64. It is just a spacer with set screws that allow air to bypass the IAC. I'm too cheap to pay that kind of money to solve my stall on hot start problem. I've grown used to catching it with a bit of accelerator when it starts up. I think I will try cutting away some of the gasket between the air holes, to allow air to bypass the IAC. It could be adjusted by trial and error by cutting away more gasket, and the gasket could even be doubled up if more bypass is needed. Anyone know why this cheapskate fix would not work?


yo,
concept could work;

"...That is an adjustable idle plate....aka....idle air metering block...aka idle-fixer. You can get it from your Ford dealer. Last one I bought for a customer's truck was about $85 and it came with new mounting screws. made my own (fixed-orfice) plate by cutting a piece of 1/8" flat bar to the shape of my IAC Valve gasket and drilling the passage holes 3/32". I started with 1/16" holes but that weren't quite large enough for my particular engine. Point there is that different engines may require their own orfice size....hence the two adjustments on the Ford (factory) version. These things have been in use for 15 years that I know of, maybe more.....which tells me that Ford has known all along that they had a design glitch in their EFI idle air valve system..."
Source: by DGW1949

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#11 BroncoJoe19

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Posted 26 September 2011 - 09:43 AM

I'd just like to add (if it hasn't already been stated) is that a vacuum leak will often give one a surging / hunting idle.

miesk5 likes to suggest using a short length of garden hose to listen for a leak. Often if the leak is bad enough to cause a surging idle, your'll be able to hear it with this technique.
BroncoJoe19... I am not a professional mechanic, nor an engineer.
One should always obtain professional advice before attempting a repair or modification.

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#12 nelbur

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Posted 30 September 2011 - 05:00 PM

I have spent some time this week trying to set up an air bypass around the IAC valve by cutting away some of the gasket between the IAC in and out air holes, rather than pay big bucks for Fords spacer kit. I cut away the center of the original IAC gasket from the outside of each hole to the outside of the other hole, giving about 1/2" gap for the air to pass through. I noticed an immediate improvement in the engines starting behavior, but it would still die occasionally.

For most of my trucks life it has been dying when it was started hot. It would rev up and then drop the idle so low it would die unless I would catch the idle with the accelerator. It would never die when cold as the IAC would keep the idle speed up, and it never died at stop lights. Now it's worst situation seems to be when it has been shut down for a half hour or so, and restarted. I wonder if the heat soak is fooling the ETC into thinking the engine is warmer than it really is.

I decided that more improvement could be had if I had a thicker gasket, because the original IAC gasket was very thin (0.018"). I had some 0.030" gasket material so I made my own with the same 1/2" cut out. This gave enough bypass to noticeably raise the idle speed and almost eliminate the dying. After maybe 50 starts in the last few days, it only died twice. After so many years of catching it with the accelerator it is darned hard to leave my foot off it. It is clear to me that by trial and error one can tune the air bypass without the need for the expensive Ford kit. I may combine the two gaskets for more bypass, but the idle is about as fast as I would want now, especially for driving in snow.
'86 302 EFI

#13 TheBus

TheBus

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Posted 17 December 2011 - 02:14 PM

Hey everyone just following up on this thread. I was able to fix the idling issue. I purchased a digital code reader make by Equss. It was around $25 and was very helpful for diagnostic purposes. I bought it so I would not have to deal with an analog meter and counting the needle sweeps, as my year Bronco is not equipped with a CEL.

Once I received the code reader I performed the engine off test. The KOEO test indicated a code 23 for the TPS sensor out of specified range. Also, the continuous memory (last 40 warm-up cycles) indicated code 53 for TPS sensor above maximum voltage. Further TPS testing with a multimeter indicated a 4.4v reading at closed throttle. This is near the max reading for the TPS as it should be around 1v at closed throttle. Moving the throttle cable to WOT read 4.9v.

Some symptoms I was experiencing with the TPS above max voltage was: Low surging and erratic idle, stalling at start-up when cold, fast idle not occurring at cold start-up, occasional too high idle (happened 2-3 times), and occasional miss/hesitation at part throttle.

Hope this helps anyone experiencing the same symptoms...
87 Bronco XLT 302



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