My suicidal high idle- non fox related....

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My suicidal high idle- non fox related....

June 16, 2014, 02:39:29 PM

Hi all. Since at the explorerforums im far from popular and nobody gives a for me and reply my topics asking for help, im finally here.

Background:

Old Ford explorer 96, 4wd (not working, suspecting hall effect sensors at the transfercase, near impossible to get them here) v6 Ohv engine. Has like 150,000 miles. Recently got coolant on the transmission. Drain flush 3 times and replacing the radiator . It behaves the same as before.

Friday i went to the firefighter station to work, i was a little late so i speeded up a bit. I noticed a little high idle, maybe 1300 rpm in D, stopped. I did not take care very much since i was on a hurry. I ended my workday like 12 hours later, and returned to home. This time, besides the normal 2000 rpm at cold startup, i noticed the idle speed was high all the way to home. I was really tired so i left that day.

Saturday i needed to go to the mall, and the idle got very high instantly, 2500 rpm. i guessed the engine will eventually get a lower rpm while driving, but no, it was really hard, i was doing like 30 mph without any trottle input. Suddendly the engine acelerated itself to 3000 rpm. I killed the engine, and returned to home.

I have already did:

*Trottle cable and trottle body are ok. These are not getting stuck anywhere. it was my first guess. I even had a helper to mash the gas plenty of time, but it looked normal.

*Mass air flow sensor is plugged in.

* Trottle position sensor appears to be working. Minimun voltage is set at .975 volts, voltage at WOT is 4.6 volts. Again, pressing the gas multiple times does not getting any value "stuck", returns to normal.

*No visible vacuum leaks, but i think i need to get this professionally checked. I dont have a vacuum detector.

*Suspecting of the IAC Valve. If i disconect the harness , nothing changes. If i remove the iac valve completely from intake manifold, it starts +and tries to climb+ to 2500 rpm, but less than a second later the engine kills off. At the inside of the iac valve there is an small spring. Its really hard and barely moves. It is not a cleanable part (anyway i tried it to no avail)

* No codes stored at the ecu. All the monitors are OK.

Before i start to throw money into this, its ok to change the IAC, or what i do first? IAC costs here 95 USD so i want to be safe, if i had to buy it, no problem, but im not the guy that only changes parts.

Thanks in advance.

My suicidal high idle- non fox related....

Reply #1 – June 16, 2014, 05:06:14 PM

Is the Explorer EEC IV or OBD II ? I think 96 was the first year they were required to be OBD II in the States.

My suicidal high idle- non fox related....

Reply #2 – June 16, 2014, 05:19:50 PM

No codes means the car isn't in limp mode. Basically your car is still able to manage the system and nothing is "broken" so to speak. I doubt you would need a new IAC since you are not showing any codes. My guess would be vacuum related issue and that should be ruled out before buying any parts to change.

My suicidal high idle- non fox related....

Reply #3 – June 16, 2014, 08:21:59 PM

I'm tending to agree with custompunk. I would try something to find the leak. I know what I'd use but you have to be very careful using it. you could also try misting water near all the vaspooge connections, intake gaskets or anywhere extra air can come in and listen for a change in rpm's. Just my .02

My suicidal high idle- non fox related....

Reply #4 – June 16, 2014, 09:51:47 PM

I heard you can take a propane torch, crack open the valve (of course don't light it) and wave it around any areas suspect for a vacuum leak. Supposedly safer than some methods. You should hear a change in engine rpm if you find one. Just an idea. Even better if you have one already.

My suicidal high idle- non fox related....

Reply #5 – June 16, 2014, 11:16:51 PM

96 is obdII, Id hook it up to my scan tool and see what the desired iac count is compared to actual. And Id also use brake kleen spraying it on the vacuum hoses trying to find the leak. If you have a scan tool read the oxygen sensors, low voltage indicates a lean condition. If your sucking air down stream of the mass air flow sensor the oxygen sensors will read lean and have low voltage. It will usually kick a p0171 and p0174 lean bank one and lean bank two. Good Luck. oh yeah is it a 4.0 sohc or push rod motor????

My suicidal high idle- non fox related....

Reply #6 – June 17, 2014, 06:35:52 AM

Have the engine smoke tested for vacuum leaks. Normally those engines have a cracked PCV hose. Look for a crack in the PCV hose Very common on that engine. Also that engine is noted for defective IAC issues, Normally an IAC issue does not store codes. I see IAC issues all the time with absolutely no codes. Pull the IAC off the engine and see if it blocks air. Try blowing air through it. If the valve is sticking open you will never be able to control the idle. Also when you remove the IAC you have to block off the port that allows air in to the throttle body or manifold. Removing the IAC creats a HUGE VACUUM LEAK. That is how the IAC works. Just saying!! Also not every code causes a LIMP IN MODE. Example EVAP LEAK! Have a good Tuesday.

My suicidal high idle- non fox related....

Reply #7 – June 17, 2014, 02:04:28 PM

Can you find something to cover/plug the IAC holes on the intake manifold? If the IAC is stuck too far open, that would make sense that disconnecting the harness did not change the engine speed. Be sure you use a small piece of sheet metal or something solid, heavy and thick to plug them so it does not get sucked into the manifold. And it will probably not want to idle well, you'll need someone to sit there and push the gas pedal a little, or move the throttle body arm by hand to keep it running.

Hopefully the IAC has not shorted internally somehow. I confirmed, for fact, that my IAC did short out. I spoke with a technician from Moates and he claimed that it is very rare but can happen. In my case, it destroyed the IAC control circuit in my computer. I sent it to someone on eBay that does Mustang 5.0 ECM repairs, and they fixed the problem. But my IAC circuit was ruined by the short, the new IAC sat there and did nothing...

You would need a big vacuum leak to cause that high of engine speed. I won't call it an "idle" because 3,000 rpm can hardly be considered an idle!!

I have unlpugged small hoses (1mm to 5mm roughly) from my intake before and not seen more than 100-200 rpms increase in idle.

My suicidal high idle- non fox related....

Reply #8 – June 17, 2014, 09:02:09 PM

You can hold your finger on the hole to do a quick test with a helper with the IAC removed or make a block off plate with thin sheet metal without the big holes. Only the mounting holes. that will confirm a bad IAC as the engine will not idle at all. And making small vacuum leaks normally do not make changes because the IAC corrects it. Have a good Tuesday night guys.

My suicidal high idle- non fox related....

Reply #9 – June 18, 2014, 01:37:44 PM

Thank you to all for your valuable input!

Asking all your questions.

1.- Yes, the explorer is OBD-2 Complaint. I have a Code Reader "Eqqus Innova 3100A" and the time i have scanned it has no codes, not even pending ones , and all the monitors were OK.

2.-I think i need to double check the vacuum related parts. There are a small tutorial on the net showing how the vacuum leaks can be found with smoke. I will give a try with that.

3.- I have heard lots of info about the water method but no reliable info about exactly how to do it. Any info of this would be appreciated.

4.- I have a propane torch for solder copper tubbing. How i can use this ?

5.- Already did this procedure with starting fluid. I sprayed all the visible piping with no noticeable changes. My Engine it is the pushrod 4.0 V6. Unluckily my code reader doesnt get live data so i cant get real time values, i only can get freeze frame data.

6.- I am going to do this test when i am at home. I am thinking to make a small aluminium part , from a beer can, and put bloking the 2 iac ports. Maybe that will make a change. I hope so. It makes sense.

7.- oopsss, Im going to try a better material, maybe some kind of plastic ? i have some small plastic sheets laying around. Also, i have heard its possible to mess the ECU from a shorted IAC, it will be fairly bad, ecu´s are very expensive here, but i hope this wouldnt be the case.

Thank you. I will post again with my findings. Have an excellent day guys !

My suicidal high idle- non fox related....

Reply #10 – June 24, 2014, 01:29:42 PM

Well, i checked all the vacuum hoses and all were correct. A friend of mine told me about a place were i could get a new IAC for 50 USD. Went there and installed it.

Everything is working fine now.

Thanks for all your input guys!