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Unread 07-08-2010, 11:17 AM   #16
meatlord
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Quote:
Originally Posted by nforcer View Post
Does yours do it if you have the air on?
Mine does it all the time, when the air is on the Idle jumps up a bit only when the compressor cycles. That is all Ive noticed. My idle does dip too low(I feel) when stopped at a light etc. I never had this issue up untill 60 days or so ago. No codes no engine light. This should not be happening, my 2000 4.0ran flawlessly on road and offroad.

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Unread 07-08-2010, 03:10 PM   #17
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Mine only does it when the air is off. If the air is on, the idle is steady and the tach does not move. Anyone?
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Unread 07-08-2010, 08:38 PM   #18
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Another question. When you unplug the IAC while the engine is running, should the engine speed change and/or the engine die? I read in another post on here that it should die...but mine does not. I took out the new IAC I bought and put the old one back in and, surprise, no change. Tomorrow I seriously look for vacuum leaks before I go to work tomorrow night...
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Unread 07-09-2010, 08:20 AM   #19
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start checking for vacumn leaks at the manifold...mine did the same thing and the manifold bolts had worked loose enough to cause it...gave em all a good snuggin up and it idled perfectly...after i had done a complete cleaning of the iac and throttle body of course..figures...
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Unread 07-09-2010, 08:47 AM   #20
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You have checked all your electrical connections in that area, yes?
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Unread 07-09-2010, 03:41 PM   #21
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Quote:
Originally Posted by restorod View Post
start checking for vacumn leaks at the manifold...mine did the same thing and the manifold bolts had worked loose enough to cause it...gave em all a good snuggin up and it idled perfectly...after i had done a complete cleaning of the iac and throttle body of course..figures...
I can't find a vacuum leak, but I took your advice and snugged up the manifold bolts. I will see how it runs on the way to work tonight.

To get to all of the manifold bolts, I had to remove that little aluminum foil heat shield. When I took it out, all of the insides crumbled. Is this shield necessary? If I remember correctly, earlier 4.0s did not have this heat shield. Also, it does not seem like it reduces temps at all in it's immediate area.

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You have checked all your electrical connections in that area, yes?
Yep, checked all of the connections...man I wish that was all it was!!!! :
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Unread 07-09-2010, 06:24 PM   #22
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OK, so I drove to work and it seems better. I did not have any low RPM drops at lights/stop signs. When I pulled into the lot at work and stopped to back into my spot, it dropped but that may have been from a quick stop, wheels at full lock and shifting into reverse. I am still getting, for lack of a better description, a slight "stutter" while at idle. This is very, very slight and might be normal?

I am thinking that I might have had/have a really small leak at the manifold. So, I will probably go around and retorque all of the bolts to factory specs. Does anyone know what the factory specs are for the intake/exhaust manifold?

Also, after doing some reading, I am thinking that tin foil shield I took out was a "debris shield." Is that correct? If so, I will not worry about putting anything back in. Thanks everyone for all the help.
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Unread 07-09-2010, 07:03 PM   #23
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Quote:
Originally Posted by nforcer View Post
OK, so I drove to work and it seems better. I did not have any low RPM drops at lights/stop signs. When I pulled into the lot at work and stopped to back into my spot, it dropped but that may have been from a quick stop, wheels at full lock and shifting into reverse. I am still getting, for lack of a better description, a slight "stutter" while at idle. This is very, very slight and might be normal?

I am thinking that I might have had/have a really small leak at the manifold. So, I will probably go around and retorque all of the bolts to factory specs. Does anyone know what the factory specs are for the intake/exhaust manifold?

Also, after doing some reading, I am thinking that tin foil shield I took out was a "debris shield." Is that correct? If so, I will not worry about putting anything back in. Thanks everyone for all the help.
I dont assume that it is "normal" mine didnt have this issue up untill 2 months ago when it started suddenly. The shield in question is suposed to be a heat shield as well( I say BS) one of the injectors suposedly gets hot and causes a stutter when restarted I was told by the dealer. They sent me a recall notice for it, but I blew them off because I installed a header and didnt have heat issues. Hope that helps some.
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Unread 07-09-2010, 07:20 PM   #24
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Quote:
Originally Posted by nforcer View Post
Also, after doing some reading, I am thinking that tin foil shield I took out was a "debris shield." Is that correct? If so, I will not worry about putting anything back in. Thanks everyone for all the help.
Yes it is.
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Originally Posted by meatlord View Post
The shield in question is suposed to be a heat shield as well( I say BS) one of the injectors suposedly gets hot and causes a stutter when restarted I was told by the dealer.
It's not the TSB for #3 injector fix, that would be an insulating sleeve that goes over the injector...
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Unread 07-09-2010, 07:38 PM   #25
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Quote:
Originally Posted by Knuckelhead View Post

It's not the TSB for #3 injector fix, that would be an insulating sleeve that goes over the injector...
I think that is probably the one he is talking about. I have the same one for mine, but I don't have a problem so I did not have it done.
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Unread 07-10-2010, 02:19 PM   #26
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Yeah...it is still doing it. I am at a loss. I think it is probably a vacuum leak somewhere, but I can not find it if there is one. The Jeep needs to throw a code and help me out! Any other ideas of what I can check? There seems to be a bunch of threads of people with similar problems but most of them don't find fixes or don't post their fixes. This can't be that hard...
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Unread 07-12-2010, 06:25 AM   #27
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OK, so I have some new info that may help with tracking down the problem. I drove the Jeep to work all weekend and it was not really doing it. On the way home this morning, I was stopped at a light on a hill. I figured I would take my foot off the brake to see it the load affected the RPMs. It did. It dropped them down to like 300 but it did not stall it out. Then, on the rest of the ride home whenever I stopped the RPMs would drop low like they were doing before. It seems like the increased load, for lack of a better explanation, flipped a switch or something???
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Unread 07-12-2010, 07:58 AM   #28
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well,you can try spraying some carb cleaner around the manifold and vacumn lines to see if the engine revs and maybe spot a vacumn leak..just be careful not to start a fire or something...it really sounds like the throttle body butterfly may be sticking,or the iac is carboned up..you said you had cleaned the tb and replaced the iac,so you wouldnt think that to be the problem,but you may look at the butterfly a little closer and make sure that it isnt sticking...the reason i say this is because of what you stated in your last post about it being okay after pulling the idle down at the uphill stoplight...you have very low miles,so u wouldnt think it would be worn,but i have seen them stick occasionally where the butterfly closes on the smooth bore of the tb...keep diggin and you will figure it out..
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