idle stumble and a howl

[dreamr]

I have posted previously with these concerns, but a lot has changed since then.

My vehicle is a 99 with a 4.0 OHV 75,000 miles.
The only performance mods are a k&N FIPK gen II, and 2.5" cat back exhaust.

My problems:
My idle has had this little stumble for a while. It is completely random, and seems to have no readily available solutions.

Recently (last 2 days) I have gotten this odd howl that stops If I tap the gas pedal. (think fog horn)

What I have done.
Plugs and wires were replaced 6,000 miles ago.
TPS adjusted to .96v 6,000 miles ago.
I have re-installed the stock intake to see if it was responsible. It wasn't the prob.
Fuel filter replaced.
Pcv valve replaced.
I took it to the dealer, they recommend servicing the injectors( I have only used techron and similar through the gas the last few tanks)
They also replaced all four cats due to internal noise.
Replace Fan clutch assembly.
Power Steering pump changed(unrelated)

I don't know where to go now. I was going to clean the IAC, but was advised that cleaning would just hide a problem, and it would still need replacement, besides it is not whistling.
I keep my engine very clean, and I have noticed that there seems to be a bit of oil leaking around the intake where it attaches to the motor (lower intake manifold gasket?)

Any help would be so very appreciated!!!!!!!!!!!!!!!!!!!!

 

[Blee1099]

Try cleaning it first.. Just make sure you let it dry before putting it back on the intake.. I didn't a few days ago and noticed a bad howl but it disappears once the IAC is completely dry.

 

[sncwfo99]

Since you have oil seeping out around the lower intake, it sounds like you have an air leak. I would try retorqueing the bolts. If that doesn't work you will need to replace the gasket.

 

[dreamr]

I think I am going to try the intake bolts, I have my manual for the torque specs, sequence and such.

However I do not have a torque wrench that measures inch pounds. Can I use my foot pound wrench, and if so, how do I measure torque?

 

[sncwfo99]

You can use the foot pound wrench, but I don't remember the conversion for doing it. Maybe someone else will chime in with the formula. Don't take my word for this, but I think it is between 8-10 lbs/in for every 1 lbs/ft of torque

 

[general x]

http://www.onlineconversion.com/ real handt dont forget

 

[dreamr]

Thanks for the replies! The conversion site was very handy.
I pulled all my plugs to check them. They were fine, I also checked resistance on the wires, and they seemed fine, so I checked resistance at the coil pack, and each individually. All were in spec.

I decided to move on to the intake bolts, but noticed that it is the upper intake, which seems to be slightly leaking. I retorqued all the bolts, and found two were out of spec by a bit. I cleaned up the area, so I should be able to see if the leak is still there. I decided to wait on the lower intake bolts untill I see if this cured my issues. The lower bolts look involved to get to anyway.

Cross your fingers for me.

Also, a question. I keep reading about the "propane method" to test for intake leaks. Could someone please explain this to me. What Is this "method"?

 

[dreamr]

hm just updating the thread. After another trip to the dealer. they claim the idle stumble is do to my aftermarket wires, and I should reinstall the motorcraft wires.

The next day it developed a nasty howl. Source IAC. It was cleaned and replaced. I haven't noticed the Idle Stumble yet, but the howl is still there just reduced

 

[geber11]

Iac

 

[jasurge]

I am new at this explorer lingo but, I know I have the same problem as "dreamr" I see he was able to dampen the situation. What is an IAC? sorry if this sounds idiotic

 

[Okrazie1]

The IAC is the Idle Air Control valve. Here's a thread (with pictures) describing the cleaning of the IAC.

 

[jasurge]

thanx for the info, the IAC was replaced and have not heard a thing since installing it three days ago!