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Discussion Starter #1
We received our new Motorcraft IAC and installed it. We also installed the IAC Spacer Kit. We repaired the damaged IAC mounting threads with 6mm x 9mm Time Serts. All Throttlebody, IAC, and upper intake gaskets were replaced.
1991 Bronco IAC and TPS boxes SMALL.jpg
IAC 1 SMALL.jpg
IAC Spacer kit F2PZ-9F939-A SMALL.jpg

The idle with IAC installed is 1200 RPM. The instructions that came with the IAC Spacer (I.S. 6273) mention adjusting one or both air Trim Screws. CCW to decrease RPM. We have turned both trim screws CW 2 turns with no change in RPM. I am getting worried that they will soon drop inside the IAC and find their way into the engine.

The throttlebody does have holes in the the throttle plates. I have read that the original throttlebody did not have holes and that holes were later added to prevent vapor lock.

Cleaned Throttle Body 1 SMALL.jpg

I have also found reference to a kit, Ford Service Kit (FOPZ-9F652-A) to block the holes on the newer throttlebody. I have found limited info and no such part to date, but I am still looking.

I am going to try putting a square of Gorilla tape over the throttleplate holes to see what happens. I will be careful not to open the plates to prevent sucking the tape into the engine.

The TPS is a new motorcraft. It has a range of 500 - 3.75k ohms.

Any help would be appreciated. Rain is predicted for the next 5 days and we are working outside in the driveway.
 

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Discussion Starter #2 (Edited)
The idle is 950 RPM With the SPOUT and IAC disconnected. The top Throttle screw was set as directed by IAC Spacer instructions. Tight on .002 shim then add 1/2 turn CW. No throttle sticking or binding.

The idle 1050 with IAC connected but SPOUT disconnected.

The idle is 1110 with SPOUT and IAC connected. Timing is 10 BTDC.

The idle is 975 with Throttle Plate holes plugged.

For grins, I backed out the Top Idle Screw 1/2 turn. The idle dropped to 860. I also noticed that the top idle screw is bent. I am going to see if the original IAC mounting screw will fit and then reset with .002 shim + 1/2 turn CW. All testing is being done with the engine warmed up.

I will remove the negative terminal and drain all codes after this because of all of the testing. We will then start and run 10 minutes and check codes. If no codes, we will take a short drive and check for codes.
 

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Did you follow the proper procedure for setting the idle? If you didn't the EEC will start tripping balls because it doesn't know what's going on.

Also, with a 950rpm with the IAC DISconnected I'd be leery of a vaccum leak, especially if the stop screw is adjusted for the plates to be pretty well closed.

Unless we are confusing these "screws" we are both referring to.
 

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Discussion Starter #4
Still searching for other leaks. All bolts are torqued to spec. All gaskets are new. Spraying near joints and vacuum junctures with either WD-40 or Starting fluid does nothing to change idle so far.

Is the Top idle stop screw always bent to impede adjustment? Or did someone at some time just happen to bend the one on this truck?
 

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Did you have a good idle to start with? A bent throttle plate adjusting screw clearly indicates that the adjustment has been tampered with. Maybe it is just a optical illusion, but you pic of the throttle body appears that the plates may be a bit open. Don't worry about the holes in the throttle plates because if that is an original TB that has not been modified, the holes are accounted for in the original EEC programming for minimum airflow.

A likely cause could be that your TPS is showing part throttle by starting with too high of voltage (above 1.1v) or more likely the throttle plates are adjusted to allow too much minimum air flow. Remove the Spacer until you obtain a good computer managed idle.

Unplug the IAC and test closed throttle body TPS voltage with KOEO to ensure less than 1v. Don't worry about the shim for adjustments. Simply adjust throttle plate screw 1/4 turn at a time with key off and IAC unplugged. Restart after each adjustment until you get 600-650 rpm. Adjusting while off and then restarting to determine idle rpm will allow the computer to redefine closed throttle body ratch for each adjustment.

When you achieve 600-650 rpm, retest the TPS for closed throttle body voltage just less that 1v. Then delete the computer memory, reconnect the IAC and restart the engine. The engine should idle at a computer/IAC managed 675-700 rpm. Allow the computer time to relearn. If you achieve a good idle, then reinstalled the spacer and work from there.
 

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Discussion Starter #6
Thank you very much Seattle. Very precise info. I will have to wait the weather out and shoot for any breaks I get. Oh, and never assume. I am recovering from one right now. We did have a good idle prior to installing the spacer.
 

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We did have a good idle prior to installing the spacer.
Then hold up on adjusting the Throttle Plate Adjuster. Remove the Idle Air Adjust Spacer and confirm a good idle.

Although the Spacer can fine tune minimum airflow, its primary purpose is to reduce carbon buildup on the throttle plates which reduces idle airflow and causes idle problems. Either of your Broncos (1991-1996) should have had a Sludge Tolerant Throttle Body which does not require cleaning nor indicate an Idle Air Adjust Spacer (hence the "holes in the throttle plates"). Removing the Teflon coating may be enough to alter the minimum airflow. I do not know as I have never done it, but your picture does show a very clean Throttle Body.

I do know that the Idle Air Adjust Spacer is typically used as indicated in TSB 95-21-07 or with modified engines.



Idle Air Adjust Spacer

Allow me to elaborate on the Idle Air Spacer for a moment. Coking on Ford EFI Throttle Blades has been a problem for many years. If the PCV or vent filter clogs, oil tends to back up and accumulate in the Throttle Bore and plate. This is also caused by blow-by from worn piston rings in older engines. The oil becomes a sludgy residue which eventually hardens reducing the expected amount of air that can pass by the closed Throttle Plate. As less air passes by the closed Throttle Plate, the EEC commands the IAC to increase air flow around the Throttle Plate to maintain a good idle. Eventually, the IAC will approach edge of it's operating range. This is the point where the symptoms of poor idle are experienced and Throttle Body/IAC cleaning are indicated.

To alleviate this problem, Ford developed the Idle Air By-pass Service Kit (F2PZ-9F939-A) for EFI Broncos prior to MY1991. The kit includes an Idle Air Adjust Spacer that corrects sludge contamination concerns on the Throttle Blades to the point that Ford no longer covered Throttle Body Cleaning under the 5/50 Emissions Warranty. A secondary benefit is the ability to fine tune closed throttle plate idle air flow without altering the TPS, which has been very popular with Mustang performance builders having idle problems. The Idle Air Bypass Kit was installed by Ford Dealerships under warranty per TSB 91-25-07 and is still available from Ford as well as aftermarket versions from Tomco and eBay.

Beginning in 1991, Ford began using a Sludge Tolerant Throttle Body design which includes a special slick Teflon coating inside the throttle bore. This coating minimizes deposit formation and does not require cleaning or the service kit. The issue is harsh cleaning can remove the sensitive Teflon coating eliminating the protective qualities. These Throttle Bodies can be identified by a black/yellow sticker on the Throttle Body warning against cleaning or adjusting. Please note that this Sludge Tolerant Design does not include the IAC which may still require servicing or replacement.






 

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Discussion Starter #9
We removed the IAC spacer and re-installed IAC. We disconnected the IAC electrical connector. Key Off - We set the idle screw until we achieved 630RPM. We reconnected the IAC and idle is 750RPM.

We removed the SPOUT and verified the timing was still at 10 BTDC.

The truck runs great. It has good power and is very responsive. Unfortunately we are getting DTC 12 and 53. We cleared codes, drained battery with lights on. Checked that codes were clear and performed KOEO Slow Codes. We got a 12 and a 53. We drained the battery and drove it for a while. Check engine light is on. DTC = 12 and 53.

We measured voltage at the TPS. Closed = .77v, Open = 4.67v.

Any ideas?
 

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Try unplugging the IAC and removing the SpOut Connector when adjusting idle minimum airflow. This will eliminate any possibility that the computer is adding timing. All throttle plate adjustments should be done with the key off, as you did. Then, once again, test the TPS KOEO.

Here is the specific Ford Idle Setting Procedure for your 5.0L. Follow the procedures to the letter:


5.0L V8: 1988 and later Truck and Van

To adjust idle speed:

1. For 1995, skip this step:

With the engine off, place a 0.050-inch feeler gauge (AT) or a 0.030-inch feeler gauge (MT) between the throttle stop screw and the throttle lever.

2. Disconnect the SPOUT connector near the ignition module and verify that base timing is within ±2° of specifications. Refer to the VECI decal. Leave the SPOUT connector disconnected until adjustment is finished.

3. Disconnect the ISC air bypass solenoid.

4. Place the transmission in neutral or park. Start the engine and let it idle for 2 minutes.

5. With the transmission in park or neutral, turn the throttle stop screw, to set the idle speed to 675 ±50 rpm for AT or 700 ±50 rpm for MT.

NOTE: If the screw must be turned in, stop the engine. Make an estimated adjustment, start the engine, and repeat steps 4 and 5 before continuing.

6. Stop the engine and disconnect the battery for at least 5 minutes.

7. Remove the feeler gauge from the throttle stop screw and reconnect the ISC air bypass solenoid. Reconnect the ignition SPOUT connector. Verify that the throttle is not stuck in the bore and that the linkage does not keep the throttle from closing.

8. Start the engine and let the idle speed stabilize. Then snap accelerate and let engine speed return to idle. Lightly depress and release the accelerator and let the engine idle. Refer to the VECI decal for curb idle specifications.

NOTE: If idle speed oscillates or is erratic, the throttle plates may be open far enough to allow canister purge flow. To verify the condition, disconnect the canister purge hose and plug it. Idle should stabilize. If purge is present at idle, the throttle plates must be closed until the rough idle stops.

9. With automatic overdrive (AOD) transmission, check throttle valve (TV) rod adjustment.
 

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Discussion Starter #11 (Edited)
We are still playing the idle game. If the idle is below 700RPM disconnected or 780 RPM spout and IAC connected, the truck will stall in reverse or taking off from a stop. We have been sneaking the Idle adjustment up prior to each start. We now have a smooth idle at 780-800 RPM with SPOUT connected and the stall is gone. We are still getting TPS DTC's. Performance is good.

We have been working on a few other problems that popped up and took priority. One problem had to be addressed because oil pressure was in question. The other two are preventing us from passing inspection.

The oil pressure gauge started dropping out intermittently. After reading some info posted by Miesk5 about the operation of the gauge, We decided to add a brass T, replace the sending unit, and install a mechanical gauge. We found some good info posted by Steve83 which was very helpful. Looks like this one is fixed, must have been the sending unit. It sure is nice being able to see a real pressure reading with the new gauge when in doubt. We used a 2" hole saw to cut a hole in the lower right dash where there was space for an uninstalled option. It came out nice. I will add a picture soon.:goodfinge
Mounted Mech OP gauge.jpg :thumbup

OP Gauge T connector with Sending Unit.jpg :rockon


The turn signals are blowing fuses and the dash /instrumentation illumination is out. We are losing continuity on the LB/R wire between the light switch and defrost switches and the fire wall. We have continuity from the Engine compartment near the firewall to a point near the fuse panel. We have continuity from the light switch to the Rear defrost and stereo. We are losing continuity somewhere near the fuse panel. We are trying to gain access to the back side of the fuse panel without ripping everything out, but this may not be possible. Any ideas? :banghead

Note: Hook one probe to Lt Bl/R in engine compartment just outside firewall and other probe to ground shows NO continuity. Connecting 1 probe to Lt Bl/R wire on back of fuse panel and other probe to ground shows continuity.

We are still removing the dash and our minds. I was hoping that the back side of the fuse panel would be easy to access. Looks like I was wrong... :banghead
 

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Discussion Starter #12 (Edited)
TP errors still present and strange starter behavior

We cleaned up the stereo wiring which was a mess. We replaced the jerry-rigged headlight switch connector with a new Motorcraft connector with pigtails. The connections were individual female spade connectors plugged into the switch. We did a solid job by soldering and heat shrink wrapping all connections.

We replaced the headlight switch (Motocraft SW 6352), because the dimmer resistance was sporadic. We also checked our grounds. The Dash lights are now working. Turn signal working for two days without blowing fuses.:rockon

Unfortunately... We had a strange problem on the way to get our inspections. The starter kept turning after key returned from Start to ON. Starter kept turning when key turned to OFF.

Based on all of the info we read and our schedule, we stopped at XL to purchase and replace the Starter Relay on the fender with a new Motocraft part. This did not fix the problem. :banghead

The next time the starter stayed ON we measured the "S" post for 12v. No voltage found. I guess we could have a bad new part. It has been raining for 3 straight days, so we have had limited time to work this problem.

Any help would be greatly appreciated. :thumbup
 

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Sounds like you may have the Starter Relay wired incorrectly or a sticky solenoid. I would double check the wiring, test, then replace the starter solenoid if no change. If you are using an older Direct Drive Starter, it may be time to upgrade to a PMGR Starter.


Direct Drive Starter Terminals:
Start - 12v wire from keyed ignition switch in the "Start" position.
Battery - All wires, except for the Starter Motor wire.
Motor - Starter Motor wire only.

PMGR Starter Terminals:
Start - 12v wire from keyed ignition switch in the "Start" position.
Battery - All wires.
Motor - New 12ga wire directly to the small terminal on the Starter Solenoid.


For Direct Drive Starter, follow this diagram.



For OEM PMGR Starter, follow this diagram.



For new PMGR Starter, follow this diagram.




If the starter temporarily continues to run for a brief period, you may have Starter Run-on induced by incorrect wiring or use of a Bus Bar to jumper the large Starter Solenoid Main Post to the small Solenoid Start Post in an attempt to eliminate the need for a separate 12v Start Wire.

See this link (pay close attention to the last section): How To Properly Wire Your PMGR Mini-Starter

 

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Discussion Starter #14
PMGR upgrade coming

I agree with your advice. I am researching PMGR starters now. I have seen your 3 terminal schematic as well as a 4 terminal schematic for upgrading to PMGR. Have you an opinion on the 4 wire vs 3 wire solution?
4 wire starter relay to PMGR diagram.jpg


I have found several Ultima Select # 32281 starters . I may have found a Motocraft SA769ARM, but will not know for sure until tomorrow.

I have found several BWD 4 terminal Starter Solenoids:
BWD Selcect 4 terminal Solenoid s5049_primary.jpg

and potentially one Motorcraft 3 terminal solenoid Part # SW1951C.
Motorcraft 3 terminal Solenoid e9tz11450b-bac.jpg

Looks like I will also require a few ft of 12ga wire for the PMGR Solenoid.

I will be replacing the large Starter wire and potentially the neg battery cable as well.
 

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Discussion Starter #15 (Edited)

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Discussion Starter #16
Mounting Stud problem moved to new thread

I opened a new thread for the problem with the broken ignition module mounting stud.:thumbup
 

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Discussion Starter #17 (Edited)
Proposed wiring for 4 terminal starter relay to PMGR Starter

The 4 Teminal relay is a Standard Motor Products S610

Based on what we have read we believe the wiring should be as pictured below. We are asking for feedback, warnings, and/or advice as to the wisdom or lack thereof with this proposed wiring scheme. :shrug
Proposed 4 terminal Standard Motors starter relay wiring.jpg
AC Delco PMGR starter terminals.jpg

Starter is AC Delco PN# 336-1114A
AC Delco PMGR Starter.jpg



Terminal, terminal, terminal, terminal, terminal, terminal, terminal, terminal, terminal, terminal, terminal, terminal, terminal, terminal, terminal, terminal, terminal, terminal, terminal, terminal, terminal, terminal, terminal, terminal, terminal, terminal, terminal...

Thus concludes my spelling lesson, or typing lesson for the day.
 

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Discussion Starter #18 (Edited)
:beerWe wired her up as posted above. She works great.:rockon
 

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Discussion Starter #19
Blew Turn Signal Fuse on way to inspection again

We took the truck for inspection hoping to pass and then get back on the IAC again. No such luck...:banghead

The Right turn signal blew while in motion and making a right hand turn. The Emergency flashers, brake lights, and dash lights all work when the fuse is blown.

We recently replaced the turn signal switch and the flasher. We went all through the steering wheel and column wiring while replacing the ignition switch and the ignition switch mounting stud.

The difficult part is that it works for several days before it blows. It only seems to blow while in motion. :barf
 

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Discussion Starter #20
Back on the IAC/TPS, high CO emissions failure

We popped a fuse in for the turn signals and ran it through the inspection. We wanted to get a reading on our emissions due to the IAC/TPS problem we have been suffering.

It failed for High levels of CO (Carbon Monoxide) at both high and low RPM:
High RPM = 3.07 vs 1.20
Low RPM = 5.79 vs 1.20

:banghead

I believe this can be caused by TPS and/or IAC issues, which we do have.
:barf
 
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