Sudden FAST idle in an SOHC

[aldive]

A few days ago ( at about 62k miles ) my 3.0 SOGC started ideling at between 1500 and 2k RPMs.

I have read all I can find and am not sure where to start in trying to fix this problem, IAC, TPS, or thermostat.( all of the above are original equip )

Any ideas will be appreciated.

 

[97emerald]

Al, as far a I know, The main things that would cause too high an idle, are bad IAC, sticking throttle, or vacuum leak. If you have no CEL I would suspect sticky throttle or a vacuum leak. I would think the IAC would trigger the light. Kenny

 

[X24]

My IAC didnt trigger a CEL. Mine was making my truck die sometimes when it was idling or coasting down the road. I replaced it about 5 months ago and havnt had a problem until today. It was idling for a bit and then died. Started right back up and did the same thing. Started it again and gave it a few revs and when the idle came down it dropped down around 500 and sounded like it was gonna die again but it leveled out. I'm thinking fuel filter now.

 

[Ray Lobato]

Al, I'm thinking it's the TPS.

 

[Agent_51]

IAC went bad on my ranger and i didnt get a CEL. It sounds like what happened with mine too. I just hopped in it one day, started it up and it was idling at 2000.

 

[jasonb]

Originally posted by aldive
A few days ago ( at about 62k miles ) my 3.0 SOGC started ideling at between 1500 and 2k RPMs.

i'd say its due to the fact that one of your liters isn't working.

if its the IAC you can try cleaning it for a temporary solution. it if gets better after cleaning it you know that's probably it. that's free to do and really quick. give that a shot first.

 

[aldive]

Looks like its a thermostat problem. I set the OBD II scanner to monitor coolant temperature and it stayed at about 230 F.

Off to replace the thermostat.

 

[jasonb]

hmm.. that's interesting. glad you got it figured out though!

 

[aldive]

When the computer reads overheat condition, it speeds up the motor to drive the fan faster to attempt to cool.

 

[jasonb]

yeah but i wouldn't assume it would be overheating at startup. i just assumed you meant idle after starting up. it makes sense if you meant idle all the time..

 

[aldive]

Agreed, the fast idle was not hapening at actual start up but after motor warmed up.

 

[Majisto]

Good thing thermostats are cheap

 

[aldive]

THE FIX

The thermostat was indeed the problem.

The new one I got at NAPA cost $19 ( with a new O ring ).

he replacement took me about 45 minutes.

 

[Majisto]

Originally posted by aldive
THE FIX

The thermostat was indeed the problem.

The new one I got at NAPA cost $19 ( with a new O ring ).

he replacement took me about 45 minutes.

$19? I saw them on sale at Autozone for $5 *thinks*

 

[aldive]

Originally posted by Majisto
$19? I saw them on sale at Autozone for $5 *thinks*

No $5 thermostat will ever go into my truck.....

 

[aldive]

After a 50 mile test run, thtemperature never exceded 192 F and stayed mostly at 190 F. This was monitored with my OBD II scanner.

 

[X24]

50 mile test run? Thats more miles than I do in 3 days.

 

[aldive]

Originally posted by 98FordX24
50 mile test run? Thats more miles than I do in 3 days.

Yup, it gave me a chance to have a great shrimp sdiner down sSouth too.

Without road testing, one cannot know if a mod works or a problem is solved. 50 miles id a short test run for me.

 

[Hollowpoint]

Question about the temp gauge

Hmmmm. Very interesting. I developed this exact problem last night. At start up she idles just fine. After about 1 - 2 minutes the idle speed actually increases. I spent the morning cleaning the MAS and IAC and resetting the computer twice. Each time I thought I had it licked, the fast idle would return after a couple of minutes. My question is why is my temp gauge not showing a high temp reading? It still reads in the normal zone. Any more help would be greatly appreciated.

I guess I should head over to the parts store and grab a new thermostat and gasket. Darn, not how I wanted to be spending my birthday.

 

[outrun84]

Had That Too

When mine did that one thing that can play a role is the thermostat, when mine went it caused the idle to go up. One thing that helps is to replace it or have it checked and take off the negative batt. cable and reset the ecu memory. The thermostat when it goes, can cause the ecu to think it is in warmup mode so it raises the idle. I replaced mine and boom perfect idle and it was nice and cool. give it a shot it is not that much trouble.