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Unread 11-28-2009, 05:54 PM   #1
Lon33
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1993 YJ Wrangler 
 
Join Date: Aug 2009
Location: Ohio
Posts: 16
Low Idle Cold, High Idle Warm

Hi, this is my first thread i've started, so here we go! My situation is slightly different than those that i read with high Idle. I have a 93 wrangler with a 4.0 engine, five speed manual transmission, and like 154,000 miles on it. When I start up my Jeep it idles just under 1000rpm's. After it runs awhile and it heats up then it starts idling around 1500 rpm's. I just noticed the other day that it seems to be getting higher and is more around 1700rpm's now.
I just bought this jeep in the summer and have been fixing it up as i go and it never used to do this. The most recent thing I did was change the Serpentine belt and then a bit after that it started to do the high idle when warmed up. My jeep does whistle so it sounds like it might have a vacuum leak, but its done that since the day i bought it and it just recently started idling high when warm. Here is a list of things i've done to it mechanically since buying, in case it helps any figuring out with whats up.
I've changed the spark plugs and wires (I used the plugs you don't have to gap), i've changed the valve cover gasket (though i don't know if it totally seated right) and the oil pan gasket, the serpentine belt, air filter, oil, some parts for the four wheel drive to work, gas lines, and a couple other unrelated things.
I just want to know what all possibilities might be wrong with my particular instance before i attempt to fix it up. Oh, also i'm not totally mechanically inclined, I'm working on getting better. I have a general idea with stuff, but i'm no pro or amature. Any help is appreciated, THANKS!!!


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Unread 12-16-2009, 08:13 PM   #2
Lon33
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1993 YJ Wrangler 
 
Join Date: Aug 2009
Location: Ohio
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Ok, not much advice going on here. So... i took some time to check my jeep over a little. I found one of the ends of one of my vacuum tubes was dry rotted really bad. I went to the dealer to replace it and they don't make that tube anymore, and they don't have any in stock anywhere. So i went to NAPA and got a tube to put there instead. It hasn't helped at all, but i'm going to get a smaller tube for the one end and splice it into the other tube because the two ends plug into different sized objects. I'm going to do this and a few other things to my YJ tomorrow, we'll see what happens.
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Unread 12-17-2009, 09:39 AM   #3
Que89YJ
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1989 YJ Wrangler 
 
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Location: Detroit, Michigan
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It sounds like you have more vacuum leaks. Use brake fluid or starter fluid and spray it around vacuum lines and the intake and listen for an idle change. Check your manifold bolts, especially the ones closest to the firewall. They have a tendancy to break
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Unread 12-20-2009, 01:27 AM   #4
Boanerges
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1992 YJ Wrangler 
 
Join Date: Dec 2009
Location: St Cloud, FL, Florida
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You should check Idle Air Controller which is attached to the back of throttle body. has 2 screws holding it on. They have a tendency to get gummed up. Unplug, remove.. watch not to drop the little black gasket, and scrub/clean with carb cleaner. The piston inside is spring loaded and should move when pushed in with some resistance.

Last edited by Boanerges; 12-20-2009 at 08:54 AM..
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Unread 12-21-2009, 05:29 PM   #5
Lon33
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Location: Ohio
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Sweet, some reply's to go off of. Ok, First of all, changing that one line didn't help at all. It went from across where one of the fuel lines goes into the fuel injector, to the middle of the fuel injector where there was a y and another vacuum line leading from it. So that didn't change anything fixing that.

I will try both of your recommendations when i get a chance to. I was wondering what would be the best way to find vacuum leaks. I will keep you posted if i find anymore leaks and if fixing them helps, or if cleaning off that Idle Air Controller helps either.
Thanks for the tips, hope they work.
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Unread 12-22-2009, 01:42 PM   #6
Lon33
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Ok, I cleaned the sensors really good and it didn't fix anything. So i started checking the lines and i was squirting some water around exerywhere to see if I could find the air leak. Well I found it. Its leaking air in where the fuel injector bolts onto the engine. So i'm going to say that is what my problem is. I'm going to try squirting some gasket seal in there to see if it helps until i can replace the exhaust and intake gasket.
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Unread 12-22-2009, 01:49 PM   #7
bigbelman2009
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1989 YJ Wrangler 
 
Join Date: Oct 2008
Location: fredericksburg, virginia
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one day last year when i was taking my buddy home i noticed my jeep was idling around 1900 and i saw the temp guage was over 220. i opened the hood and it was pissing antifreeze. i found out that the hotter it got the higher it idled. idk if thats what your problem is but i was just throwin it out there
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Unread 01-07-2010, 03:51 PM   #8
Lon33
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1993 YJ Wrangler 
 
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Location: Ohio
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Ok, so far as i can tell I have found what my problem was. I just finished replacing my intak/exhaust gasket because here it was letting in air. It has been doing that since i bought it this summer. Holy crap, it fixed so many issues i had. My high idle when warm is GONE! The whistle i have had is gone, it runs smoother and better, and has more power now too. Plus it is idleing a little lower than it did before too! THIS IS AWESOME!!!!!!!!!!!!
So again, my intake/exhaust gasket was bad and needed replaced. Thank you guys for your help, i wouldn't of figured it out on my own without some guidance and trouble shooting.
THIS FORUM IS FREAKIN AWESOME!!!!!!!!!!!!!!!!!!!!!
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Unread 10-26-2014, 04:25 AM   #9
Dago82
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I have almost same problem. When engine is cool idle is normal 900-1000rpm also when engine is warm idle is ok as long i drive highway, but when i drive on city where is lots of traffic lights it starts to gain idle. I think that when engine gets cool air flow through it works, but when in city airflow is minimal it start to gain idle to 1500-2000rpm. Allmost all hoses is changed and and it looks that intake/exhaust gasket has been changed resently.
What could be the problem?
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Unread 10-26-2014, 04:26 AM   #10
Dago82
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I have almost same problem. When engine is cool idle is normal 900-1000rpm also when engine is warm idle is ok as long i drive highway, but when i drive on city where is lots of traffic lights it starts to gain idle. I think that when engine gets cool air flow through it works, but when in city airflow is minimal it start to gain idle to 1500-2000rpm. Allmost all hoses is changed and and it looks that intake/exhaust gasket has been changed resently.
What could be the problem?
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Unread 10-26-2014, 10:41 AM   #11
mike134
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1989 YJ Wrangler 
 
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Location: Cleveland, OH
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Quote:
Originally Posted by Que89YJ View Post
It sounds like you have more vacuum leaks. Use brake fluid or starter fluid and spray it around vacuum lines and the intake and listen for an idle change. Check your manifold bolts, especially the ones closest to the firewall. They have a tendancy to break
Just a note for anyone reading this thread: Que meant to use brake cleaner fluid, not brake fluid.

Quote:
Originally Posted by Dago82 View Post
I have almost same problem. When engine is cool idle is normal 900-1000rpm also when engine is warm idle is ok as long i drive highway, but when i drive on city where is lots of traffic lights it starts to gain idle. I think that when engine gets cool air flow through it works, but when in city airflow is minimal it start to gain idle to 1500-2000rpm. Allmost all hoses is changed and and it looks that intake/exhaust gasket has been changed resently.
What could be the problem?
Did you spray water, brake cleaner, carb cleaner, or starter fluid on the vacuum lines to find vacuum leaks?
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Unread 10-29-2014, 03:45 PM   #12
Tony01
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1994 YJ Wrangler 
 
Join Date: Apr 2010
Location: Bicester United Kingdom
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Checking for vacuum leaks is very simple, start the engine and spray either carb cleaner or brake cleaner spray onto the ends of the vacuum leads inc map sensor leads and onto the inlet manifold where it bolts onto the engine. Do not spray too much as it is highly flammable, just quick bursts. Any change in engine speed or sound and you have found your leek.
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Unread 10-29-2014, 05:03 PM   #13
Que89YJ
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1989 YJ Wrangler 
 
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Lol thanks for that one! That could've been ugly!
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Unread 10-29-2014, 10:24 PM   #14
mike134
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lol, its good if you want to repaint the engine compartment!
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