4.6 Rough Idle issue

[Midnightride]

Hello everyone, new to the forums and hoping for some help. I just purchased a 2002 explorer with the 4.6 setup. I am very familiar with the 4.6 setup as I have one in my 1998 expedition. I have cleaned the IAC and throttle body and soon to swap the stock plugs. Is there anything else that is typical on these to cause a rough idle? All vacuum hoses and lines have been checked adn appear to be good.There is no lack in power, it just runs rough at idle. I have scanned for codes already with nothing popping up. I also have the famous wheel chatter issue which I found a great thread on here about already. Any help with this would be much appreciated. I will soon post some pics of my setup and rig. Thanks!

 

[newby 75]

driver side cylinder head exhaust valves issue...

 

[Midnightride]

Is that a common issue on the 4.6 for these? I am guessing the 4.6 setup is different on these than the one I am running in my expedition. I did the PI head swap on it and have the newer Mustang GT (01-04) heads with the NPI bottom end. Anything else that it could be other than this? Also do you have a link to more info on the exhaust valve issue? Thanks.

 

[HiImBrian]

Is that a common issue on the 4.6 for these? I am guessing the 4.6 setup is different on these than the one I am running in my expedition. I did the PI head swap on it and have the newer Mustang GT (01-04) heads with the NPI bottom end. Anything else that it could be other than this? Also do you have a link to more info on the exhaust valve issue? Thanks.

No. That is not a common issue at all. It is the same set up as you have on your expedition. I did Stage I PI heads on my ex and that area is not the issue.

Ford decided to go with a plastic intake manifold which tends to crack after a while. Your best bet is to pull that off and look for cracks. Then replace with new intake manifold gaskets.

Sometimes just cleaning the idle air control valve doesn't do the trick. I would go and pick up a new one and see if that takes care of your problem.

Your EGR could also be clogged. I don't suppose you've checked for any codes?

 

[Midnightride]

Scanned for codes already and nothing popped up. I am working on swapping all the plugs now and see that the intake gasket for sure is bad. This setup looks the same as the 01-04 Mustang GT with the throttle body rotated 90 degrees and plumbed air intake to the passenger side. On my Expy the throttle body runs forward and out the driver side due to the setup being slightly different with the truck intake. Also cleaned the IAC and it didn't do much either. Prob will pull the EGR and clean it out today and see if that works. For some reason some knuckle head swapped the stock plugs with Denso plugs which is stupid for a domestic and especially how finicky a Ford can be about plugs. Will post up results after its all done.

 

[HiImBrian]

Take care while removing the EGR to not bend or break the EGR tube. It is very brittle.

It may not just be the manifold gaskets, but the manifold itself. Like I said they were made of plastic and have this odd foam enclosure around them so it's hard to tell when they break. If you're mechanically inclined at all I would still recommend pulling it off and just giving it a good once over. Just break off all that extra foam garbage as it is really not necessary and look it over well for cracks. I know when mine was broken it would have sort of a "hiccup" every once in a while.

 

[Midnightride]

I def agree with pulling it and checking for cracks. I should hopefully be able to get to that next weekend. I took ti for a test drive a bit ago and it runs a bit smoother but still has a small bit of rough idle. Thinking like you were saying there is a crack in the intake which I know would also cause a rough idle. Will post up more info as I go along with this project.

 

[Midnightride]

Got everything put back together and still has a bit of a rough idle but not quite as bad as before. Hopefully the intake check and gaskets will do the trick. Its my wifes rig and I am into it for 5K purchase price only because of a mint interior and plenty of extra body mods. Trying not to sink much cash into it.

 

[rocco123]

Did u look at the 90 degree elbow leading into the idle air valve? There isva sticky at top of this forum about it. Many people including myself found it split and leaking air. Rubber get soft

 

[Adam Black]

The wires and coil are just as important as the plugs. Just because you have good plugs doesn't mean you have sufficient spark.

 

[Midnightride]

Checked the elbow and it looked just fine. As far as the coils I am going to swap the intake gasket first before I drop $55 a piece for the coil pack replacement. I am finding that its a common issue for the Expedition and Explorer for leaking intake gaskets which I know can cause a ton of issues. The plan is to swap it out this weekend. I know I also need to swap out the timing chain tensioners due to them not being replaced when the timing chain was replaced previously. Then it will be checking the tranny fluid again and swapping the coil pack in the rear end. Longer list of things to do than I wanted but cost seems to be staying relatively low for this.