idle RPM

[bluexplorer1]

hey guys. does anyone know what the idle should be on a healthy engine. i have a 2000 4.0 SOHC with a rough, pulsing idle when my foot is on the brake and the vehicle is in drive. the RPM when this is occuring is 500 exactly. in neutral, the idle is only slightly higher (needle just barely off the 500 mark) and the vibration is not as rough. this also occurs in R. is this normal? could this be a vacuum leak? clogged injectors?

 

[Lost216]

Mine used to sit at 500 even for a long time in neutral/park until I added the intake. It sounds like you might want to clean your MAF first, since it's the easiest thing to try and cant hurt. It's in the routine maintenence(sp?) section of the main site.

 

[VOATMJ1]

If your idle is "pulsing" and it is a 500 rpm, that is too low. I have a 2000, and it idles in park a hair below the 1K mark and about 950 in drive. I would check your IAC first and then the MAF!

 

[Lazzman]

I have the same problem you have a weak idle around 500rpm.

Since my truck has no other performance issues I must assume that the IAC is not operating correctly. I did test it according to the article on this site with an ohm meter and got some funny readings.

I replaced the IAC with an Echlin unit from Napa last February, I don't really trust aftermarket parts- I will eventually dump it and put in the Motorcraft version.

Try testing it with a volt meter and see how it turns out.

 

[aldive]

The idle speed should be: 750 - 830 RPM with an auto tranny.

 

[bluexplorer1]

how do i test the IAC with a voltmeter? where do i hook it up? what is the voltage supposed to be?

 

[Lazzman]

I don't have the link to the thread but you test three different area's. I beleive one is for ohm resistance and the others are for volts.

I remember I could not get any resistance reading between the IAC motor and the actual valve, which got me thinking that the motor was probably not working right.

It is my understanding that at idle the motor should pull back the spring and let more air in to regulate the idle, if the air is not let in then the idle will be to rich.

 

[ma96782]

IAC Cleaning:

http://www.explorerforum.com/forums/showthread.php?t=84220&highlight=iac



And, another IAC Cleaning thread:

http://www.moddedmustangs.com/cleaning-your-iac.html


Aloha, Mark


PS....checkout these also:


TPS adjustment:

http://www.explorerforum.com/forums/showthread.php?t=79362

Idle speed adjustment:

http://www.mysporttrac.com/mysporttrac/projects/IdleAdjust/IdleAdjust.htm

 

[Green98XLT]

Note- the IAC on the SOHC and OHV are in totally different locations and look much different.

MA96782- your links are for the OHV motors only, could confuse some.

 

[Zero Signal]

I picked up a bottle of QD Contact Cleaner at Home Depot. It is a residue-free electronics cleaner. I removed the IAC and sprayed the inside with the cleaner, then took a cotton swab to clean out the gunk. I managed to clean a LOT of crap out of both sides of the IAC.

The cotton swab was handy for cleaning the plunger, and in between the coils on the spring. I would alternate scrubbing with the cotton swab, and "rinsing" with a squirt or two of the cleaner.

LET IT DRY COMPLETELY before you start your truck

 

[bluexplorer1]

more questions...

well in my efforts to fix my rough idle, i have done a few things. first, i ran a can of seafoam through the pcv valve and 1/3-1/2 a can through the brake booster. when i put the seafoam through the pcv valve i shut the truck off waited 10 minutes and restarted it and i got absolutely NO smoke. then i put some in the brake booster and it smoked like a chimney. doing this seemed to clean up my "pulsing idle" but did not clean up the roughness. i took it for a test drive on the highway and the acceleration problem is still there. cruising at around 40-55 mph (with steady pressure on the gas pedal about 1/4 of the way down) and then trying to accelerate (applying more steady pressure to the gas pedal without lifting up my foot) the vehicle will still accelerate but the RPMs will not jump up (downshift) until i have gotten to about 3/4 of pedal. then later on, i tried to adjust the idle speed by turning the screw on the throttle body in accordance with this thread: http://www.mysporttrac.com/mysporttrac/projects/IdleAdjust/IdleAdjust.htm

now according to my scangauge II my idle in park is about 800RPM and my idle in drive is about 700RPM and it is alot smoother. this still has not resolved my "acceleration issues".

Now for the questions...

1) Aldive, should the idle speed be 750-830 in "P" or "D"?

2) Could i have just made more problems for myself by messing with that
screw on the throttlebody? Could it mask other problems that could
be giving me a rough idle?

3) Why didn't i get any smoke when i put the seafoam in through the
PCV valve?

4) Could my "problems" with my acceleration be normal? my ranger kind of does the same thing,
but i don't think it should be used as a reliable comparison.

Any help would be appreciated.

 

[gensic11]

so im guessing my 600 rpm idle is too low?

 

[Green98XLT]

I had the low/choppy idle on my SOHC and just did the throttle body mods discussed in the other thread and found my idle speed went back up to 800-900rpm in park and idle really smoothed out. I think 850-900rpm is normal.

I did not bore or port the throttle body whatsoever, just cleaned it very well, half-shafted the throttle shaft, smoothed the butterfly screws off and polished the blade.

Overall, it was easy to do and took me less than 1.5 hours with a Dremel. I do still have that hesitation before the trans kicks down, my Ex has done that since day one, I think its just a fault in the programming/shift patterns. It takes 3/4 throttle to get it to kick into 3rd and really gets on my nerves. Trans is a low mileage ford reman 5R55 with a full Transgo valve body kit as well.

 

[dynamite196]

clean the maf and iac first as well as the injectors, 1000 is too high it really shouldnt be over 750 even with an auto, i havent seen any car with an auto higher than that when the engine was in good shape.

 

[cfd911]

i have a 2001 xlt with the sohc i took off the throttle body cleaned it did a complete tune up with motorcraft plugs and wires took off iac to check it , i havn t had any problems with the motor prior to the maintance mine idles at approx 600-650 in drive and is smooth.. i would just check the simple things first ie injector cleaner in tank throttle body ,plugs wires iac clean, clean map check for vacuum leaks. good luck

 

[Raminator157]

Mine is idleing rough also. Its at the line below 1. But seems to idle alright when is cold out, but once it warms up it acts funny. It idles like it wants to stall. I cleaned the throttle body and put in a new K&N air filter. From what Iam reading, I should clean the IAC? Iam not geting a houle noise though. When I put it in drive, I can feel some vibration and some jerkyness when Iam driving down the road. When I have it stoped and in drive, the rpm still acts like it wants to stall.

 

[edward1985]

I went out 4wding the other week, went through abit of mud and got my explorer airborne. Now it is running very low at idle, about 500 and down to 400 sometimes. looks like ill be checking all these things this weekend

 

[kimwa]

Mine is sitting at 1000

The idle speed should be: 750 - 830 RPM with an auto tranny.

rpm when warm. So what do you think I should do?

 

[EB4X]

Mine is sitting at 1000

rpm when warm. So what do you think I should do?

Could be a vacuum leak...check vacuum lines for cracks.. ....how does it run?