4.0 SOHC High Idle Fixed... - Ford Truck Enthusiasts Forums



4.0 SOHC High Idle Fixed...

Reply
 
 
 
Thread Tools Search this Thread
  #1  
Old 10-27-2007, 02:33 PM
javi2001's Avatar
javi2001 javi2001 is offline
Posting Guru
Thread Starter
 
Join Date: Apr 2003
Location: Venezuela
Posts: 1,143
javi2001 is starting off with a positive reputation.
Exclamation 4.0 SOHC High Idle Fixed...

Hi there, after spend several months doing research on How to fix my High Idle condition on my Explorer 1998, after doing a lot a repairs, replaced parts, it seems to me I found the problem....

I did all service required to fix any vacuum leak, new IAC, cleaning all connectors, new intake gaskets, no errors codes, no nothing just the engine sometimes gets the idle increased between 800 to 1500 RPM then I did this...

1º Using a needle, measured sensed voltage at TPS while engine Idle and Hot. I found 1.092 Vdc
2º When the engine start increasing idle took readings again and found 1.116 Vdc !!! but the throttle plate was in its stop pin, so why the voltage is now higher???

Reading some old ford manuals (4.9L, feddback carby, 1986) I found the TPS voltage should be around 0.850 to 0.900 Vdc while idle. The old PCM ignore any voltage between 0.900 to 1.000 Vdc because the internal voltage reference regulator can supply voltages between 4.950 to 5.050Vdc depending on the PCM temperature.

It explain why sometimes the TPS and all other sensor can return minor voltage differences even registering the same engine condition, then I guessing... Probably the PCM Internal Voltage reference regulator on my explorer was producing the voltage variation but the TPS voltage still been so high so I did...

3º Using pliers I did turn the Throttle Stop Pin back while measuring voltage at TPS signal wire and found the voltage was reduced from 1.116 to 1.060 Vdc and the Idle immediately return to normal 650 RPM !!!

4º After doing some more test and experimentation I found the PCM ignores any TPS voltage under 1.100 and the minimum TPS voltage I could obtain was 0.960Vdc after using several different TPS sensors.

It makes me think: when the PCM receives voltages over 1.100 Vdc "Think" the driver is light pressing gas pedal then it respond increasing Idle by commanding IAC to do so...!!!

5º I found also the TPS screws let a minor TPS sensor rotation also, just a few degrees but enough to increase the TPS voltage over the ignored limit of 1.100Vdc.

Problem Fixed, just adjust the TPS sensor to the lower possible voltage and if still not been enough, move slightly the Throttle Stop until the TPS voltage is reduce under 1.100 Vdc.

WARNING: Be sure the throttle plate still making stop over the Stop pin, not in the internal wall of the Throttle body or wall damage/wear will appear.

Last edited by javi2001; 10-27-2007 at 02:40 PM.
Reply With Quote
  #2  
Old 06-20-2011, 11:18 PM
daughtersbronco daughtersbronco is offline
New User
 
Join Date: Jun 2010
Location: Lake Havasu City, AZ
Posts: 6
daughtersbronco is starting off with a positive reputation.
Brilliant!

I was researching a similar problem on a 2001 Explorer and found your ideas right on the mark. You did a detailed job.
Seems like one of those $.10 problems that can take forever to solve and will drive you nuts. Thanks for your help.
Reply With Quote
  #3  
Old 06-22-2011, 09:31 PM
javi2001's Avatar
javi2001 javi2001 is offline
Posting Guru
Thread Starter
 
Join Date: Apr 2003
Location: Venezuela
Posts: 1,143
javi2001 is starting off with a positive reputation.
I'm Glad it was helpfull.
Reply With Quote
  #4  
Old 06-23-2012, 09:30 AM
Crash=7 Crash=7 is offline
New User
 
Join Date: Jun 2012
Posts: 2
Crash=7 is starting off with a positive reputation.
Great information! I did all you recommended, but still had a problem. I was having a high idle that was temperature related. Cold start was OK, but as engine warmed up to "normal", idle would be 1000-2000 RPMs. I looked at the Temp. Gauge and saw that it was reading higher than normal, but thought that it was related to the 93 degree outside Temp. I decided to change the Thermostat and problem has been solved!
Reply With Quote
  #5  
Old 10-05-2012, 12:44 PM
manuelronk manuelronk is offline
New User
 
Join Date: Oct 2012
Posts: 1
manuelronk is starting off with a positive reputation.
Quote:
Originally Posted by javi2001 View Post
Hi there, after spend several months doing research on How to fix my High Idle condition on my Explorer 1998, after doing a lot a repairs, replaced parts, it seems to me I found the problem....

I did all service required to fix any vacuum leak, new IAC, cleaning all connectors, new intake gaskets, no errors codes, no nothing just the engine sometimes gets the idle increased between 800 to 1500 RPM then I did this...

1º Using a needle, measured sensed voltage at TPS while engine Idle and Hot. I found 1.092 Vdc
2º When the engine start increasing idle took readings again and found 1.116 Vdc !!! but the throttle plate was in its stop pin, so why the voltage is now higher???

Reading some old ford manuals (4.9L, feddback carby, 1986) I found the TPS voltage should be around 0.850 to 0.900 Vdc while idle. The old PCM ignore any voltage between 0.900 to 1.000 Vdc because the internal voltage reference regulator can supply voltages between 4.950 to 5.050Vdc depending on the PCM temperature.

It explain why sometimes the TPS and all other sensor can return minor voltage differences even registering the same engine condition, then I guessing... Probably the PCM Internal Voltage reference regulator on my explorer was producing the voltage variation but the TPS voltage still been so high so I did...

3º Using pliers I did turn the Throttle Stop Pin back while measuring voltage at TPS signal wire and found the voltage was reduced from 1.116 to 1.060 Vdc and the Idle immediately return to normal 650 RPM !!!

4º After doing some more test and experimentation I found the PCM ignores any TPS voltage under 1.100 and the minimum TPS voltage I could obtain was 0.960Vdc after using several different TPS sensors.

It makes me think: when the PCM receives voltages over 1.100 Vdc "Think" the driver is light pressing gas pedal then it respond increasing Idle by commanding IAC to do so...!!!

5º I found also the TPS screws let a minor TPS sensor rotation also, just a few degrees but enough to increase the TPS voltage over the ignored limit of 1.100Vdc.

Problem Fixed, just adjust the TPS sensor to the lower possible voltage and if still not been enough, move slightly the Throttle Stop until the TPS voltage is reduce under 1.100 Vdc.

WARNING: Be sure the throttle plate still making stop over the Stop pin, not in the internal wall of the Throttle body or wall damage/wear will appear.
hola! hablas español?? tengo el mismo problema
Reply With Quote
 
 
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
93 2.3l MAF sensor yonu 4 Cylinder Engines 0 02-03-2015 07:21 PM
IAC Trouble bkbkbkbk Ford Inline Six, 200, 250, 4.9L / 300 3 09-07-2014 07:08 PM
Bad Map sensor? 1987 F150 4.9 87oldtimer 1987 - 1996 F150 & Larger F-Series Trucks 1 06-07-2014 05:37 PM
Runs Rich High Idle No Power PCM? 87f250banks Ranger & B-Series 19 04-02-2011 10:03 AM
IAC issue all4ford 1987 - 1996 F150 & Larger F-Series Trucks 10 06-08-2008 07:24 PM


Go Back   Ford Truck Enthusiasts Forums > >

Tags
40, adjustment, explorer, ford, high, idle, intake, leak, sensor, sohc, stop, tps, truck, trucks, vacuum

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Forum Jump


All times are GMT -5. The time now is 08:32 PM.