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Unread 11-05-2009, 07:43 AM   #1
MDonovan8
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1994 YJ Wrangler 
 
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'94 Low Idle Issues

Ok, searched the thread and could not find any thread that was like my issue. My '94 4.0 idles at 300 - 400 rpm's, no matter if the engine is hot, cold, at a stop light or after I back it out of garage. It does not want to stall at any point and it also does not hesitate when jumping on the throttle. O2, MAP and TPS senors were all bought new to get Jeep to pass Emissions (only to find out it was Catalytic Converter). Issue basically started after new Cat. Conv. was installed. Plugs, wires, cap and rotor were all changed out about 8000 miles ago along with the radiator. Cleaned the cap and rotor, barely any build up. This issuse does not bother me too much, because fuel milage has stayed about the same, but if this is hurting the engine or is componets then I need to take action.

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Unread 11-05-2009, 08:57 AM   #2
RebuildRookie
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Not sure if it would actually "hurt" the engine and components, but have you tried resetting your PCM/ECU, (whatever controls the engine on yours). Just disco the battery, I would do it overnight this weekend, and let the PCM/ECU reprogram itself since you have changed so many things. Thats what I would do.
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Unread 11-06-2009, 08:30 PM   #3
MDonovan8
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I have reset the PCM/ECU and have checked the codes but have none. I am curious about this only if it leads to bigger problems that I am trying to head off. The only explanation I have been to come up with is that the TPS was faulty when I bought it, so I will put the old one back in this weekend and see what happens.
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Unread 11-10-2009, 07:52 PM   #4
MDonovan8
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Ok, so I put the old TPS back in and nothing changed, so I put the new one back in and still the idle is about 300-400 rpm's. Any other things I can check out.
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Unread 03-01-2010, 07:23 AM   #5
MDonovan8
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Idle issue revisited

Quote:
Originally Posted by MDonovan8 View Post
Ok, searched the thread and could not find any thread that was like my issue. My '94 4.0 idles at 300 - 400 rpm's, no matter if the engine is hot, cold, at a stop light or after I back it out of garage. It does not want to stall at any point and it also does not hesitate when jumping on the throttle. O2, MAP and TPS senors were all bought new to get Jeep to pass Emissions (only to find out it was Catalytic Converter). Issue basically started after new Cat. Conv. was installed. Plugs, wires, cap and rotor were all changed out about 8000 miles ago along with the radiator. Cleaned the cap and rotor, barely any build up. This issuse does not bother me too much, because fuel milage has stayed about the same, but if this is hurting the engine or is componets then I need to take action.
Just to get everyone caught upto date on this issue. Posted this back in November and no one had any ideas. Now I had to replace my battery this weekend becuase the low idle does not turn the altenator fast enough to keep up especially at night. Also tranny is starting to delay in shifting. So in other words low idle will mess up other components. I have not figured this issue out yet, have replaced the TPS and now the only option left is to replace computer. Right now I hold gas pedal down at stop lights to keep idle up.
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Unread 03-01-2010, 06:40 PM   #6
kingweedwacker
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have you checked your vacume lines or vacume buster
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Unread 03-02-2010, 07:22 AM   #7
MDonovan8
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Checked all vacuum lines and basically everything in this motor compartment to see what is wrong.
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Unread 03-02-2010, 11:09 AM   #8
Que89YJ
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Pull you IAC sensor and motor and cleand them. Get yourself a can of brake cleaner and spray around for a vacuum leak(Usually you will go high idle for a vacuum leak) Last but most important. Get a timing light and check your advance. Iam willing to bet you are off on the timing. My .02
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Unread 03-03-2010, 06:31 AM   #9
MDonovan8
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I already have a timing light but it won't work on the 94' since timing adjustments are done automatically. Checked (before) timing anyway and it is adjusted right. There is no leak in any vacuum lines.
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Unread 03-03-2010, 11:24 AM   #10
Que89YJ
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Then IAC is the logical check. There is a post here on cleaning it. I cant find it. Usually it is a stall not a good low idle but clean the IAC motor and sensor. quick and easy and it seams logical it what you are dealing with as well.

Last edited by Que89YJ; 03-16-2010 at 10:34 AM..
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Unread 03-03-2010, 11:46 AM   #11
5.7YJ
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As Que89YJ stated, clean the IAC valve but also clean the throttle body passages and the throttle plate.
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Unread 03-09-2010, 07:47 PM   #12
kingweedwacker
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check you plug gaps and you cap and roter also is there any leaks in your exhaust before your o2 that might be throwing it off how much draw is on your battery when it is running. do you have a shorts. your alternater could be draging you engine down. is one of your pullys sticking like a bad bearing or your belt is way too tight take your cat off again and see what you could have mest with it might be somthing stupid like something got stuck in your exhaust when you put it on


if not sell the mother****er and get a better one

no dont do that i still have a 96 grand limited in my driveway with a bent frame and bad trans ill use it for something
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Unread 03-09-2010, 07:51 PM   #13
bigred94
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just take off the t.b and turn up the idile srew..
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Unread 03-16-2010, 07:20 AM   #14
MDonovan8
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Quote:
Originally Posted by Que89YJ View Post
Then IAC is the logical check. There is a post here on cleaning it. I cant find it. Usually it is a stall not a good low idle but clean the IAC motot and sensor. quick and easy and it seams logical it what you are dealing with as well.
Still don't know exactly what this IAC is, but as far as all my research goes I don't have this on the 94'. As far a the plugs/gap those are in spec range and there is no drag from the pulleys, because I checked that when I took the alt. and battery in to be checked.
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Unread 03-16-2010, 07:26 AM   #15
MDonovan8
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Quote:
Originally Posted by bigred94 View Post
just take off the t.b and turn up the idile srew..
There is no idle screw. The TPS takes care of the idle automatically. There is an ajustment screw to change the TPS, but it does not change the idle as much as I need it to.
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