Vacuum Leak Idle Problem

[monkeydude3]

Hello all~

I have a 1994 explorer, 4 door, 4.0L OHV engine with a 5 speed tranny. 2 wheel drive. She's got 136,000 miles, rolls like it has 50k and the block is super nice and solid. I've been battling an idling problem and a vacuum leak problem. It idles too fast, at about 900 rpm average, whereas normally it idled at 700 or so and had a nice rumble, but now it just hums. Also when I go under the hood I can hear a hissing coming from the intake manifold / vacuum line area.... I've inspected every vacuum line and replaced a few that appeared bad. The idle wanders too sometimes, jumping up, slowing down, etc. Any idea what could cause this? could my IAC be bad? Is there another vacuum line I'm missing somewhere? What is making me cringe is everything is gradually pointing closer to my lower intake gaskets leaking. No biggie in difficulty, it will just require patience and time. Has anyone had to replace all your intake gaskets (and subsequently your valve cover gaskets)? I was wondering what problems you ran into and if anyone has pictures or tips on doing this. Any input would be welcomed, It is still cold outside here and I will wait some time until it warms up to do this work... she still runs, but it's pissing me off. Take care all

GEORGE

 

[unclemeat]

Check the connections of the vacumm lines. 10-year old rubber tends to degrade. Use a mechanic stethiscope to determine where the leak location.

 

[monkeydude3]

ok well I inspected all of the lines and connections and so far have come up empty handed. I replaced two that looked cracked. Could the lower intake be leaking enough to make this hissing sound and also cause the idle to act up? thanks!!!

 

[nascar_intimid]

Try re-torquing the bolts on the intake. I've heard they come loose sometimes...just a thought.

 

[Rhett]

If you can't find a hose leak, it could be the IAC, from what you describe. Sometimes you never will get a check engine code with some of those vac leaks.

Also check the (plastic) intake tube for scuffing and cracks. After a long time they tend to start cracking out.

 

[lwn]

I've been fighting a simular problem, after checking every pin in the breakout box and every electrical connector I had no luck but mine would idle at 1200 to 1500. To make a long story short, I went to Autozone got a bottle of Textron fuel injector cleaner and it has ideled fine since.

 

[Flat Top]

I found the rubber grommet on the brake booster the check valve goes into leaking on my 91

 

[monkeydude3]

Oh, I will definitely look into the brake booster grommet!! As for the fuel injector cleaner.... they are all brand new, $130 a piece.... they are working great, so it's a simple stupid vacuum leak or intake leak, thanks all for your help!!!

 

[Allen35540]

No idle and surging in hot soak restart on 1995 Eddie Bauer

I have been fighting a similar problem gentleman! My 1995 Eddie Bauer with the 4.0 OHV V6 runs perfectly normal from cold and then driving at operating temperature. Upon restart, the vehicle will not idle, it dies immediately taking your foot off the gas! After I manage to get it to idle, it surges up and down and will actually surge low enough to stall. It runs rough and erratic. During the whole time no check engine codes are being stored...weird! If you let the truck cool completely down, it starts and runs completely normal! The MAF sensor was found very dirty and the fuel filter was restricted but the vehicle still has this problem. It's particularly problematic on hot days after the air conditioner has been running. Does anyone have any idea what this is? My mechanic and I are completely stumped!

 

[Swif]

My cousin has a 97 4x4 v6 explorer. idles high forgot the p codes. When i looked up the P code is was leading to a vacuum leak. I can hear the leak coming from back side of the upper intake man. I file around and there is a "T" fitting with vacuum lines. I tired to look at the line, but do not have a lot of room. I have come to find that the larger hose seems to be leaking causing a high idle, around 1500 RPM.

My question is what hose is it? as I stated it is a larger hose seem to run to the block and maybe to the right by the top of the bell housing. I need help locating a diagram and if I need to remove the upper intake man. there is a house that runs from the drive's side to the back of the upper intake man. to a "T" fitting, to the hose that seems to be leaking and the other side of the "T" fiting goes to the IAC I think from memory.

Can you guys point me in the right direction?

Thanks