Rough idle after it's warmed up or sitting at a light.

[upchuck310]

I dont know where to start? There is no warning light so no codes. The 96 ford explorer starts fine. Let it idle for a minute or two after it warms up the rough idle starts and it gets worse, sounds and feels like its got a big lopie cam in it.Now if you take of driving its fine till you stop at a light. A minute or two after sitting there here comes the ruff idle again. I have noticed that sometimes when you come to a stop the idle drops to 400 or 500 rpm the returns to normal. Idle usually is at 700 to 900 sitting still. The rig sat garaged for two years has fuel stablizer and the seafoam added. Has had 5 to 6 tanks of fuel ran threw it. Does it have to die to generate a code or is it not code related?
96 ford explorer sport
4.0 liter, manual
four wheel drive

 

[Sams01XplrSprt]

welcome

 

[upchuck310]

Thank you for the welcome

 

[dogfriend]

Welcome, search for "IAC". I think yours is sticking, which can cause the low idle speed.

 

[fixxxer]

(hint) http://www.explorerforum.com/forums/showthread.php?t=84220

 

[BrooklynBay]

Welcome to this forum! A tune up along with replacing your PCV, air filter, and fuel filter should help in addition to the above mentioned advice.

 

[upchuck310]

fixed one code now still have the other

I still have one code po174 . Explorer went from trying to die when coming to a stop. Now idle raising to almost 2000 rpm when pushing in the clutch.Pretty rough idle, tries to die after idleing for a few minutes.
Things Ive changed
fuel filter
spark plugs
spark plug wires
thermastat
air filter
IAC
Things I tested
O2 sensor
vacumm test was good
cleaned egr
temp sensor
throttle position sensor
any ideas why this is happening

 

[BrooklynBay]

Check the intake manifold gasket, and the vacuum lines for leaks.

 

[dogfriend]

I second checking for vacuum leaks. The IAC should be able to control the idle speed even when the clutch is depressed, but if you have a vacuum leak, it will let in extra air, which defeats the purpose of the IAC. Make sure the IAC gasket is not leaking; this would also be a vacuum leak.

 

[upchuck310]

checking for vacuum leak

What other things can you do to find a vacuum leak?
We coated the whole intake with carb cleaner no change.
Vacuum test with a vacuum gauge showed good ,used the test,
floating around on one of these forums ,idle 19 to 22,rev it drops 2 inches,then goes to 24.

 

[dogfriend]

http://www.explorerforum.com/forums/showthread.php?t=144852&highlight=propane

Also, for other causes of P0174 (P0171) see the thread below:

http://www.explorerforum.com/forums/showthread.php?t=145587&highlight=p0171

 

[upchuck310]

found the problem

The gasket for the EGR valve tube going into the intake just infront of the IAC
was hard and distorted. Another great idea from ford, use rubber on a warm EGR tube hope they re not making shuttle parts.

THANKS TO ALL WHO HAD GREAT IDEAS TO SOLVE THIS PROBLEM
Im sure I will be back soon for answers on how to fix my exploder
thank you again

 

[BrooklynBay]

Thanks for the update!

 

[alohamonte]

Nice find

Does the IAC supposed to have a gasket?

 

[dogfriend]

Nice find

Does the IAC supposed to have a gasket?

Yes, on my 97, it has an o-ring that has the shape of a figure 8.

Basically, any leaks after the MAF will admit unmetered air which will throw off the A/F ratio. Besides the vacuum lines on the manifold and manifold gasket(s), other possible vacuum leaks are the IAC gasket, the EGR gaskets and the o-rings where the injectors are inserted into the manifold.

 

[alohamonte]

Do you know if that gasket is available for purchase separately from the IAC? I believe my gasket is shot.

I have a weak idle. I cleaned and tighten up the IAC. It improved for maybe 2 days now the surging is coming back slowly getting worse. The IAC was replaced by Ford about 20,000 miles ago so it should have plenty of life in it. I believe the gasket may be the problem.

 

[dogfriend]

Yes, the gasket can be purchased separately. It was about $6 at the dealer, but that was several years ago (2002?) You could try fastpartsnetwork.com to see what their price is for the OEM gasket. You could also try aftermarket (Napa, Autozone, et. al.)

 

[BrooklynBay]

You could also check WWW.RockAuto.Com.