high idle problem on a 4.0

[Ranger44]

SOME CODES!

MAF may not be dirty. May be bad, or the connector. Check the connector. Very carefully. Look for corrosion and make sure the contacts are staying in place.

Now with the IAC (IDLE AIR CONTROL) valve. Do the same thing. Check the connector over.

With the PCM, it thinks off what it knows. If the MAF is reading like it's pulling little air in the PCM is like, oh shit, not very much air. Open IAC. Then your 2,000rpm happens.

I'd be looking that MAF over very carefully. Maybe replace with a known good before throwing money at a new one.

 

[eastwildlife1965]

this might help
1991 - 1997 Ford Ranger 2.3L
1998 - 1998 Ford Ranger 2.5L
1991 - 1992 Ford Ranger 2.9L
1991 - 1998 Ford Ranger 3.0L
1991 - 1998 Ford Ranger 4.0L



Symptom: Idles high all the time. Possible KOER codes 12, 13, 411, 412 or P1506. (mass air flow (MAF) sensor or vane air flow (VAF) sensor equipped vehicles only)



System: Emissions/PCM/Fuel



Codes: 12, 13, 411, 412, P1506



Problem: The idle air control (IAC) solenoid is stuck open causing high idle speed.



Test & Fix: The first step in testing is to unplug the idle air control (IAC) solenoid two-wire connector to see if idle speed drops. If the idle speed is still high, check for anything that could block the throttle plates open or for damage of the throttle plates due to wear or binding. If the throttle plates are not damaged or worn and the set screw is not holding it open, remove the IAC solenoid and block the air passages. If the RPM drops to normal or stalls, the IAC solenoid as it is stuck in the open position causing an excessive amount of air to constantly bypass the throttle plates. Replace the IAC solenoid.

 

[mailboxman]

once again you guys are all great!! I really appreciate your responses and concerns for a prob that is bugging me--unlike some others on this forum, my truck still runs fine through all of this i just have to deal with this excessive idle and not a broke down truck.

This truck has 165,000 miles but is in excellent condition--all wiring and underhood components clean and like new--i havent found any corrosion on any connectors under the hood.

I replaced the IAC a while ago--when I unplug it, the idle goes way down around 600rpm--which is a little low but acceptable--the only issues I have with running with this iac unpluggged are the cold idle issues--will not idle correctly on cold startup--as soon as i plug the iac back in idle jumps to 1200rpm warm.

Last nite I pulled the maf out and checked continuity on both wires--all checked good--i took some fine steel wool and cleaned (very carefully) both wires-sprayed again w
maf cleaner-reinstalled and no change!!!

If i was real smart I would take this to ford and have properly diagnosed, but being a dumb uneducated hillbilly out on the farm I would rather torture myself (and you guys) and fix this thing myself. I dont know where I am going to get a MAF at but there is a U-Pull junkyard about 20 miles from my house--might be easier and cheaper if i just go buy the MaF from the autoparts??

 

[TrexMex]

If i was real smart I would take this to ford and have properly diagnosed, but being a dumb uneducated hillbilly out on the farm I would rather torture myself (and you guys) and fix this thing myself. I dont know where I am going to get a MAF at but there is a U-Pull junkyard about 20 miles from my house--might be easier and cheaper if i just go buy the MaF from the autoparts??

Let's put it this way: Most of the people in this forum are uneducated hillbillies with an inexplicable and stubborn urge for self-education (no pun intended) So you don't know anyone with a 93-97 4.0 Ranger or 92-95 explorer that you could hook up yout MAF and see if you can replicate your problem in his/her truck/expo? What happens if you just disconnect your MAF?

 

[mailboxman]

I dont know--but I will let you know after lunch--i will go out and unplug it

 

[mailboxman]

Bought a new maf (remanufactured) at lunch today $66.00
I had enough time to put it on and start truck and drive back to work--idle was still high when I pulled into work--about 1 mile-- i shut truck off and restarted and idle went from 500 to 1000, then down to 550 and back to 900 until finally settling around 700

Might be fixed!!!!!

will let you all know

 

[TrexMex]

Bought a new maf (remanufactured) at lunch today $66.00
I had enough time to put it on and start truck and drive back to work--idle was still high when I pulled into work--about 1 mile-- i shut truck off and restarted and idle went from 500 to 1000, then down to 550 and back to 900 until finally settling around 700

Might be fixed!!!!!

will let you all know

Glad to hear!!!

 

[Ranger44]

Good, very good.

Those IAC codes may be stored from before you replaced the IAC. Why'd you replace the IAC?

Btw, never use any thing to physically clean the MAF filaments. Just use the cleaner and MAF specified cleaner only. Using anything other than a MAF cleaner (sprayed or rubbed) WILL damage the MAF.

 

[Forceful.3]

Haha, I idle at 1-1.2k normally, never thought anything of it really, Till I noticed when I left it on for a few that it dropped down to the 700-900 range, So I guess it's time to buy a new IAC haha.

 

[mailboxman]

Didnt fix it guys!!! But a couple of things I noticed--If i shut the truck off and immediately restart it--the idle goes down to about 700 until I start driving and back up it goes--very cold this morning and I noticed that the temp gauge never made it to where it is supposed to be???? Also although there was heat, not as much as I like---I wonder if my thermostat is causing a problem??? Temp gauge has always been fine but i had to change anti freeze twice because the system was so dirty when I got it--i also had taken out the radiator and ran the garden hose through it----

What do some of these guys mean when they say you need to burp the system on a 4.0???

 

[mailboxman]

tried the old cardboard in front of the radiator trick, and id didnt make any difference---THIS SUCKS--

I think the biggest thing bothering me is the cold idle when first started seems to scream at almost 2000 rpm--after about 3-4 minutes it goes down to 1500, and then around 1200 when fully warm. If i shut it off and restart immediately while warm, the idle goes down to around 700 rpm but goes back up as soon as i try driving.

I really need to take this somewhere and get diagnosed---its starting to posess me!!!! lol

 

[mht95ranger]

Just wondering if you had any updates? Did you end up taking it to Ford?

 

[mailboxman]

negative on the fix--i replaced every sensor under the hood including maf-tps-ats-cts-thermostat-and probanly a couple of others that i cant remember--i am thinking now it is the fuel pressure regulator--when i unplug the vacuum line it makes no difference--vacuum is still a strong 20 on this line--i understand the regulator is supposed to lower fuel pressure to the injectors at high vacuum situations like idle and deceleration--and increase pressure on acceleration--my regulator is definitely not leaking fuel--i unplugged the vacuum line and blocked and drove around that way--only difference i noticed was idle hanging a little more between shifts---i am trying to locate a fuel pressure guage to confirm--this part makes sense because i am pretty sure high idle is not vacuum or electrical related---anybody know more about this regulator??how should truck behave with vacuum line disconnected????????

 

[xdoomx]

Replaced IAC valve?

 

[mht95ranger]

someone on here said if you pull the vacuum line and there is fuel in it that the fpr is bad?