96 explorer 4.0 rough idle on every start

[96eb96]

ok, i have done 2 things this morning

96eb96, i unhooked the electrical connection off of the solenoid under the battery tray like you were talking about, took it around the block, got it up to running temp came back and parked it. started it back up with it still unplugged, no change. killed it plugged it back in and started it, no change. both times i heard the leak.

then i remember when i was getting my iac valve at autozone they guy said there were 2 different ones. so thinking i might have gotten the wrong one, i started it back up and unhooked the iac valve, it dropped down from 1000rpm to about 600 rpm and the leaking noise went away as soon as i unplugged it!

as soon as i plugged it back in the noise comes back like something is leaking.

now this iac valve i bought was brand new.

maybe i have the wrong one?

do you have your old one?

 

[mudbug0426]

i dont

usually i keep all of the parts i take off.

the 2 valves autozone has look a little different.

one has a silver knob and one has a black plastic one like my original valve did.

the one i have on there now has the silver knob. im not sure what they do or are for.

 

[mudbug0426]

ok, someone told me to try unplugging the maf sensor whilke it was running and see if it idles and better with it unplugged. it does seem to idle a little better.

with it plugged in, most of the time it idles like it would if i had a bigger camshaft, it has some lope in the idle

when i unplug it, within a second or two that lope goes away and it has more of a steady idle, its still fairly rough both unplugged and plugged in.

would this mean the maf sensor could be bad? if it was wouldnt it throw a code for it?

or could this be because of this leak somewhere, and with it unplugged, the computer doesnt know how much air is coming in the motor, therefor it doesnt know there is air being sucked in elsewhere that would cause this problem to begin with?

 

[desertbum8]

ok, well i just replaced that 3rd o2 sensor.. it helped a little bit but not enough for that to be the cause of the problem.. im going to drive it for a couple of days and see what happens. im also going to try and replace as many vaccume lines as i can get to with rubber hoses, none are cracked or broken that i can see but everytime i open the hood to do something i always seem to break another one so i might as well replace them.. does anyone have any tips on how to check for a vaccume leak?

Are you sure you replaced the right o2 sensor? There should be 2 pre-cat and 2 post-cat. If you replaced the post-cat one on the wrong bank then it wouldn't have made much of a difference.

 

[SensRanger]

FWIW, I'm on my 3rd IAC, and it's on it's way out again...making that whistling sound any time I'm not on the throttle. Maybe if you know someone with a similar year 4L Ex/Ranger you can trade to see if your problem gets fixed. Or try exchanging your IAC? It's a crummy part. And I've had both the silver tip and black tip nub. I think they are basically the same, but am not certain.

 

[mudbug0426]

Desertbum8, I have 2 sensors before the cat, and 1 after and I have replaced all three..

Sensranger, how can I check to see if it is the iac valve?

This problem is getting worse. Now it doesn’t want to idle at all hardly.

 

[gtyates]

I would guess upper intake gaskets. Had to replace mine a year ago. Same symptoms, and same CEL codes. Basically, where the plastic intake meets the metal is where the problem occurs.

 

[mudbug0426]

i have already replaced the upper intake gaskets, that was one of the first things i did

 

[96eb96]

i have already replaced the upper intake gaskets, that was one of the first things i did

you know there is also a gasket under the fuel rail....I know they can fail and let air in.

 

[mudbug0426]

i replaced that one too. took off the fuel rail cleaned it and took out the injectors and made sure they were clean

 

[96eb96]

i replaced that one too. took off the fuel rail cleaned it and took out the injectors and made sure they were clean

still thinking about that initial vac rush..
what about the brake booster? It is a major vac connection to the engine. Maybe take it off(plug the line) and see? bad check valve perhaps? could be dumping air in and making noise in the intake...

 

[mudbug0426]

ill try that right now and see what happens

 

[mudbug0426]

it runs the same

 

[mudbug0426]

96eb96, do you know where i could find a vacuum line diagram?

since i dont know where every line is, that might help me.. if it is a vacuum line problem

 

[96eb96]

96eb96, do you know where i could find a vacuum line diagram?

since i dont know where every line is, that might help me.. if it is a vacuum line problem

download the manual from my sig. if not PM me and I'll try to get some diagrams. You could block off all manifold vac ports to eliminate all external vac issues.

the other thing is the o ring around the egr tube that goes into the black manifold. that could be another leak source. also the throttle body gasket. are you sure all the bolts are tight when you did the intake?

 

[mudbug0426]

Ok ill try to download it and see what I can find.

Im kind of confused, block off all manifold vac ports? I think I have an idea of what you mean but not entirely sure.

Ill try checking that o-ring when I can find enough time to pull the top half off, I hate doing it, it’s a pain in the ass

The gasket for the throttle body is good, replaced not too long ago. And all of the bolts are tight, I double checked when I did that intake gasket.

 

[96eb96]

Ok ill try to download it and see what I can find.

Im kind of confused, block off all manifold vac ports? I think I have an idea of what you mean but not entirely sure.

Ill try checking that o-ring when I can find enough time to pull the top half off, I hate doing it, it’s a pain in the ass

The gasket for the throttle body is good, replaced not too long ago. And all of the bolts are tight, I double checked when I did that intake gasket.

the o ring area would be a good case for propane or carb cleaner.

I'm thinking about disconnecting anything and everything vacuum related that goes into the intake manifold and plugging it. But a vac diagram would be helpful too.

I dont remember..did you check fuel pressure? That can cause lean codes too. There is even a vac line to the fuel pressure regulator, but I don't think that is the issue.

 

[mudbug0426]

Ill try the carb cleaner around the o-ring area in the morning. That might be a very possible cause of this whole thing.. ive taken that upper manifold off 2 or 3 times now and that o-ring has never been replaced.. and if that is the problem, then on startup it would take that time for it to seal back up before it starts to idle right correct?

And I did replace the major vacuum lines, including the one going to the fuel pressure regulator.

No I never check the fuel pressure, I really doubt it’s a fuel problem.. within my last 3 tanks of gas my mpg has dropped from 14.9, 3 tanks ago.. to 11.2, my last tank. All in the city, I rarely drive on the highway.

I have not noticed any loss of power at all. And if the motor wasn’t getting enough fuel, wouldn’t I get better mpg to a certain extent?


if the o-ring isnt the problem, ill check the fuel pressure next

 

[mudbug0426]

ok i checked that o-ring today and im not sure about it. if you look in the pictures you can see how i could move it up and down and where it was pretty loose around the tube.. is it suppose to be like that or is it suppose to be nice and tight?

see how much it moves up and down? is that normal?

also, there were no holes or cracks on the end of that egr tube.

and another thing.. when i took off my upper intake, this is what the fuel rail looked like..

i replaced those rubber seals that pop inside the intake, should there be oil or whatever that is on the fuel rail? maybe a sealing problem?

 

[96eb96]

well the egr tube sure has to make a positive seal. Its hard to tell from the picture, but I believe should be some holding strength to the rubber when you put it on the fittings. Not sure if the gasket is supposed to fill that entire gap. Its probably very cheap at the dealer though.

The gasket surface should be spotless clean. Is there any residue from the old gasket?