Stock XJ Cherokee Tech. All XJ Non-modified/stock questions go here XJ (84-01)
All OEM related XJ specific tech. Examples, no start, general maintenance or anything that's stock.

3krpm idle

Thread Tools
 
Search this Thread
 
Old Nov 15, 2014 | 06:27 PM
  #1  
mr white's Avatar
Thread Starter
CF Veteran
 
Joined: Aug 2011
Posts: 3,648
Likes: 4
Model: Cherokee
Default 3krpm idle

My intake manifold worked itself loose, my idle jumped to 3500 RPM. I tightened it back down and made sure it was seated properly, but it's still sitting at 3kprm now. The battery gauge was originally at zero before when it happened and the check gauges light came on. Now, it sits at around 12V.

Does anyone have any ideas?
Reply
Old Nov 15, 2014 | 06:31 PM
  #2  
Crazy 8s's Avatar
Senior Member
 
Joined: Sep 2014
Posts: 896
Likes: 2
From: Phoenix, A-to-Z
Year: 1988
Model: Cherokee
Engine: 4.0
Default

The manifold gasket may be damaged/leaking. My $0.02
Reply
Old Nov 15, 2014 | 06:36 PM
  #3  
mr white's Avatar
Thread Starter
CF Veteran
 
Joined: Aug 2011
Posts: 3,648
Likes: 4
Model: Cherokee
Default

I was hoping no one was going to say that. I swore I was never going to screw with that again after the first time.
Reply
Old Nov 15, 2014 | 07:03 PM
  #4  
Crazy 8s's Avatar
Senior Member
 
Joined: Sep 2014
Posts: 896
Likes: 2
From: Phoenix, A-to-Z
Year: 1988
Model: Cherokee
Engine: 4.0
Default

If the manifold fell off, some hoses may have popped out with it. MAP sensor hose perhaps? I don't know if that would result in fast idle.

The intake gasket forms to the shape of the intake surface and the head surface. If it gets shifted a bit, the imperfections in the mating surface that got pressed into the gasket when it was first installed may not align just right and would result in vacuum leaks. You can use a stethoscope to find out for sure...
Reply
Old Nov 15, 2014 | 08:15 PM
  #5  
BlueRidgeMark's Avatar
CF Veteran
10 Year Member
Liked
Loved
Community Favorite
 
Joined: May 2012
Posts: 7,965
Likes: 964
From: Lost in the wilds of Virginia
Year: 1998 Classic (I'll get it running soon....) and 02 Grand
Model: Cherokee (XJ)
Engine: 4.0
Default

Originally Posted by Crazy 8s
If the manifold fell off, some hoses may have popped out with it. MAP sensor hose perhaps? I don't know if that would result in fast idle.

The intake gasket forms to the shape of the intake surface and the head surface. If it gets shifted a bit, the imperfections in the mating surface that got pressed into the gasket when it was first installed may not align just right and would result in vacuum leaks. You can use a stethoscope to find out for sure...

Yep, to all of the above.

IF you don't have a stethoscope, try spraying brake cleaner or WD-40 around the area where the gasket is. If there's a leak there, you'll hear it.
Reply
Old Nov 16, 2014 | 07:38 AM
  #6  
mr white's Avatar
Thread Starter
CF Veteran
 
Joined: Aug 2011
Posts: 3,648
Likes: 4
Model: Cherokee
Default

Originally Posted by BlueRidgeMark

Yep, to all of the above.

IF you don't have a stethoscope, try spraying brake cleaner or WD-40 around the area where the gasket is. If there's a leak there, you'll hear it.
I'll try this later on this week.
Reply
Old Nov 17, 2014 | 05:24 PM
  #7  
mr white's Avatar
Thread Starter
CF Veteran
 
Joined: Aug 2011
Posts: 3,648
Likes: 4
Model: Cherokee
Default

I sprayed some pb blast around there, didn't really hear anything different. I'll probably just go ahead and replace the IAC and clean the TB. I'll probably just replace the TPS too while I'm messing around.

**** I may just go ***** out and get a new gasket and new bolts too and just replace that gasket while I'm at it. Anything else while I'm in there rooting around? I'll get the motor mounts done finally too I guess.

Last edited by mr white; Nov 17, 2014 at 05:30 PM.
Reply
Old Nov 17, 2014 | 08:47 PM
  #8  
'90Cherokee's Avatar
Senior Member
 
Joined: Nov 2014
Posts: 603
Likes: 1
From: Hacienda Heights
Year: 1990
Model: Cherokee
Engine: 4.0
Default

Originally Posted by BlueRidgeMark
Yep, to all of the above.

IF you don't have a stethoscope, try spraying brake cleaner or WD-40 around the area where the gasket is. If there's a leak there, you'll hear it.
Never use brake cleaner for this or any other operation where it'll be burnt in the engine, it can kill you. Most cautions are over rated but this is for real. It can cause permanent severe lung damage severely shortening your life and even instant death.
Reply
Old Nov 17, 2014 | 09:17 PM
  #9  
salad's Avatar
Herp Derp Jerp
Premium Member
 
Joined: Nov 2011
Posts: 18,251
Likes: 17
From: Parham, ON
Year: 1999
Model: Cherokee
Engine: 4.0L OBD-II
Default

Originally Posted by '90Cherokee

Never use brake cleaner for this or any other operation where it'll be burnt in the engine, it can kill you. Most cautions are over rated but this is for real. It can cause permanent severe lung damage severely shortening your life and even instant death.
What on earth kind of brake cleaner are you using??? Stuff I buy is nearly lighter fluid
Reply
Old Nov 18, 2014 | 05:15 AM
  #10  
mr white's Avatar
Thread Starter
CF Veteran
 
Joined: Aug 2011
Posts: 3,648
Likes: 4
Model: Cherokee
Default

I only buy the non chlorinated kind anyway.
Reply
Old Nov 18, 2014 | 06:07 AM
  #11  
BlueRidgeMark's Avatar
CF Veteran
10 Year Member
Liked
Loved
Community Favorite
 
Joined: May 2012
Posts: 7,965
Likes: 964
From: Lost in the wilds of Virginia
Year: 1998 Classic (I'll get it running soon....) and 02 Grand
Model: Cherokee (XJ)
Engine: 4.0
Default

Originally Posted by salad
What on earth kind of brake cleaner are you using??? Stuff I buy is nearly lighter fluid

Whoops! I think he's right, Green Leafy One. When I read his post I remembered being warned about that in a welding class I took a few weeks ago. It turns into phosgene, which is a nasty nerve agent.

https://duckduckgo.com/?q=brake+clea...to+nerve+agent
Reply
Old Nov 18, 2014 | 06:32 AM
  #12  
salad's Avatar
Herp Derp Jerp
Premium Member
 
Joined: Nov 2011
Posts: 18,251
Likes: 17
From: Parham, ON
Year: 1999
Model: Cherokee
Engine: 4.0L OBD-II
Default

Originally Posted by BlueRidgeMark

Whoops! I think he's right, Green Leafy One. When I read his post I remembered being warned about that in a welding class I took a few weeks ago. It turns into phosgene, which is a nasty nerve agent.

https://duckduckgo.com/?q=brake+clea...to+nerve+agent
I suppose that's right. Like Mr White I only buy non-chlorinated hexane or heptane (can't remember which - I've got cans of each) and I think there's an alcohol in there too. No chlorinated or TFE crap. Come to think of it the TFE stuff would probably cause some other fun problems.
Reply
Old Nov 18, 2014 | 07:17 AM
  #13  
BlueRidgeMark's Avatar
CF Veteran
10 Year Member
Liked
Loved
Community Favorite
 
Joined: May 2012
Posts: 7,965
Likes: 964
From: Lost in the wilds of Virginia
Year: 1998 Classic (I'll get it running soon....) and 02 Grand
Model: Cherokee (XJ)
Engine: 4.0
Default

Okay, turns out it's not a nerve agent, it turns into hydrochloric acid when it hits your lungs and sinuses.

For any reading who think this is no big deal, please read this:

By the next Monday, nine days after the poisoning, I lost all balance. I was confused and could hardly talk, so I finally went to the emergency room. My symtoms were low O2 level, sugar levels out of control, vertigo, and I was hurting badly in my entire chest. I was admited and put into ICU. My kidneys had probably shut down for those first four days. My lungs were damaged, so I had to be on O2. I had to be on insulin to keep my sugar in check. Since there is no antidote for phosgene, all I could do was try and rest and hope I got better. After CT, MRI, EKG, and EEG tests, as well as several blood tests it looked like, at least for now, there is no permanent damage. However, the MRI showed fluid in my sinuses and a buildup of fluids near my brain. The phosgene scarred my sinuses, which then became infected. The three doctors I saw said I was really luck to make it.

After four weeks, it appears that I may have emphysema and chronic bronchitis. I'm on nasal medicine and an inhaler. My sinuses are severely scarred, and my smell nerves are damaged. I still have that awful chlorine taste and smell. I may also have pancreas damage. The insulin that I was taking had little effect on my sugar levels, so I'm now on some stronger medicines.
Reply
Old Nov 18, 2014 | 08:45 AM
  #14  
salad's Avatar
Herp Derp Jerp
Premium Member
 
Joined: Nov 2011
Posts: 18,251
Likes: 17
From: Parham, ON
Year: 1999
Model: Cherokee
Engine: 4.0L OBD-II
Default

Yeah... The chlorinated stuff is bad news.
Reply
Old Nov 18, 2014 | 10:22 AM
  #15  
'90Cherokee's Avatar
Senior Member
 
Joined: Nov 2014
Posts: 603
Likes: 1
From: Hacienda Heights
Year: 1990
Model: Cherokee
Engine: 4.0
Default

20+ years ago I used some brake clean on a carburetor on a running engine. I caught a whiff of the exhaust and it paralyzed my diaphragm, couldn't breath in or out. It didn't last a long time, just enough to freak me out. Many years later I read the story BlueRidge posted. I was lucky to not get enough in to do major damage. Some formulations may not have these effects but I've just made it a rule to not mix fire and brake cleaner.

The other issue with spraying brake clean ***** nilly on a motor is that it attacks plastic, rubber, sealants, paint, etc.
Reply



All times are GMT -5. The time now is 11:21 PM.