Hanging idle returns after cleaning 10pin multiple times!!!

67coupe

Founding Member
Apr 5, 2002
658
409
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Huntsville, AL
First, I have read and followed the Surge Idle Checklist multiple times. Yet, I still have the hanging idle (1600rpms) that is always temporarily fixed after an ignition cycle. Because of this, I'm almost certain its an issue with the TPS.

The following has been replace or cleaned in the last 4 years:

TPS sensor is one year old (3rd overall).
IAC is 2 years old (2nd overal).
TB is 1 year old.
10 pin connectors have been cleaned and spread/closed 3 times.
TPS connector has been cleaned and spread/closed 3 times.
Plastic vacuum lines replaced.
New PCV valve, grommet, and filter.

After all parts replacements/trouble shooting..the idle has been reset using the proper method.

Cleaning the 10pins and TPS connector seems to work....for about 6 months. Then the problem returns. :shrug:

I'm thinking it's one of two possibilities.

1) Harness problem? The car has 160,000 miles and I'm beginning to think all the intake installs (3) has possibly broken a brittle wire in the engine harness.

2) The multple cleaning and spreading of the 10pins and TPS has fubar'ed the terminals. Is it possible to eliminate these cursed connectors and solder the wires together? I'm learning toward doing this anyway. I love the thought of never dealing with these connectors again!!!!!

I'm at a loss and was hoping the Stangnet community could offer some insight as to helping me find the root cause and a permanent fix.
 
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The TPS is indeed suspect when you get an idle that goes high and then returns to normal when the ignition switch is turned off and back on again.

The 10 pin connectors can be replaced with aircraft style cannon plugs for a weatherproof connection. Use MS3101A181P (male) and MS3101A18-1S (female) at $45 each, need 2 male and 2 female connectors. You will also need the back shell and rubber boot, which will add some more $ to the price tag. See Alvatek » MIL-C-5015 Solder TypeCylindrical Connectors for more information.

For less $$$ on the repair parts, use the OEM style connectors and pins. See http://rjminjectiontech.com/ for more information. They can sell you new pins and sockets along with a crimp tool to replace the existing defective sockets and pins.
 
Thanks for the info, jrichker. I was not aware there were alternatives for these connectors.

Before I go to all this trouble. What checks can I perform to insure the integrity of the wires?

Ohm out the wires to the ECU terminals? What ohms value is considered okay?
 
What brand TPS are you using?
Chain store ones are junk and don't last long.
When i had a similar issue to yours, it was indeed the tps.
 
I never cleaned any connectors.
My problem was also some time ago.

I ONLY use genuine ford replacement sensors.
I'd rather have an original off a junk car, than a new one from a chain store.
Chain store parts are pure crap, and that goes double for electronics. I'm done learning that lesson the hard way.
 
Thanks for the info, jrichker. I was not aware there were alternatives for these connectors.

Before I go to all this trouble. What checks can I perform to insure the integrity of the wires?

Ohm out the wires to the ECU terminals? What ohms value is considered okay?

Resistance of the wire between the body side 10 pin connector pin and its matching pin on the computer wiring connector should be no more than 1.5 ohms. Tip to tip wiring from the sensor socket to the computer wiring connector should not be more than 2 ohms.

The Cannon connector option will cost you more than $200 for 2 Cannon plugs and 2 Cannon socket assemblies, so I would consider the RJM Injection Tech option first.

The one thing I can say for the Cannon plugs is that they are extremely durable and reliable if they are correctly assembled and installed. They are used on all types of aircraft around the world.
 
Resistance of the wire between the body side 10 pin connector pin and its matching pin on the computer wiring connector should be no more than 1.5 ohms. Tip to tip wiring from the sensor socket to the computer wiring connector should not be more than 2 ohms.

The Cannon connector option will cost you more than $200 for 2 Cannon plugs and 2 Cannon socket assemblies, so I would consider the RJM Injection Tech option first.

The one thing I can say for the Cannon plugs is that they are extremely durable and reliable if they are correctly assembled and installed. They are used on all types of aircraft around the world.

Just want to clarify before I start trouble shooting tomorrow.

Disconnect battery first.

For black wire on the TPS:

Measure btw TPS connector and pin 46 on ECU connector - less than 2 ohms
Measure btw body side white 10 pin (pin 1) and pin 46 on ECU connector - less than 1.5 ohms

For red wire on TPS:

Measure btw TPS connector and pin 26 on ECU connector - less than 2 ohms
Measure btw body side white 10 pin (pin 2) and pin 26 on ECU connector - less than 1.5 ohms

For green wire on TPS:

Measure btw TPS connector and pin 47 on ECU connector - less than 2 ohms
Measure btw body side white 10 pin (pin 5) and pin 47 on ECU connector - less than 1.5 ohms

My dad uses the Canon plugs for project at work. How is the durability of the RJM connectors and terminals?

Thanks again for your help!

Edit: Do you see any problems eliminating the connectors and solder the wire permanently?
 
About the time one of the connectors for a sensor fails, you will find that you can no longer simply disconnect the 10 pin harness and replace the engine EFI harness.

Plus if you pull the engine out of the car, you will have to remove the upper manifold and all the plumbing to remove the engine EFI harness. With the 10 pin connectors in place and working, simply disconnect them to pull the engine.

The RJM connectors and pins are duplicates of the Ford OEM stuff.
 
You've given me enough reasons to leave some sort of connector in place. :nice:

As far as the trouble shooting method, do I have the correct wires at the TPS, pins at the salt and pepper shakers, and pins at the ECU connector?

If my 10 pins are the problem, I would expect to see high resistance values when measuring between the TPS and ECU?

If the wire harness itself is the issue, I would also see high resistances values measuring btw the body side 10pins and the ECU?
 
You've given me enough reasons to leave some sort of connector in place. :nice:

As far as the trouble shooting method, do I have the correct wires at the TPS, pins at the salt and pepper shakers, and pins at the ECU connector?

If my 10 pins are the problem, I would expect to see high resistance values when measuring between the TPS and ECU?

If the wire harness itself is the issue, I would also see high resistances values measuring btw the body side 10pins and the ECU?

Yes. You are correct.
 
Update!

I wanted to give an update for any future searches. Once again, cleaning the 10 pins has solved the problem. No more hanging idle. Overall, the engine starts, idles, and drives much much smoother.

I measured the resistance for all three wires in TPS circuit after cleaning the 10 pins. All three were under 0.5 ohms while shaking the 10pins, so the harness looks good.

jrichker,

Thanks again for you help. I'll probably replace the 10 pin connectors with the rmj stuff during an engine rebuild later this summer.
 
hey, i also have an 89 5.0, do you know anything about rack and pinions? my wheel pulls left all the way on it's own, then right all the way...

Project89,
Might be a little better of an idea for you to make a new post, specifying exactly what happens in your situation.

When you are on the page with a 5.0 tech heading, then click "new post".
The entire forum is based on 5.0 mustangs, not just this post here.

Edit: I see that you already did. Not sure why you added this one.
Have some patience, people will reply.
 
Scroll down to topic #6 in this link:

Help me create the "Surging Idle Checklist" - Mustang Forums at StangNet

1) Separate the connector.
2) Use a small round file or something similar to clean the terminals.
3) Spray/soak the terminals using contact cleaner.
4) Using a seal pick or very small screw driver, spread the male terminals and close the female terminals. Don't get carried away. A little goes a long way here.
5) Apply di-electric grease.
6) Re-assemble.