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Unread 09-19-2013, 06:29 PM   #1
Firefyter-Emt
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1995 YJ Wrangler 
 
Join Date: Aug 2005
Location: Northeast CT
Posts: 586
Idle question

An somebody check this for me? I want someone with a good running 4cyl Jeep (newer YJ) to watch the idle speed. I want to know what the rpm drops to when shifting normal, and if you shift slow (double clutched). Also, if you drop it in neutral around 45mph, what does it do? How low will the idle drop. Also, at warm idle, where do you sit?

Thanks.... I am still fighting an idle problem!

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Unread 09-19-2013, 06:32 PM   #2
Firefyter-Emt
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And better yet, does anyone have access to a Solus scanner that they could drive around with and check IAC readings? That would be awesome to have numbers to reference off.
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Unread 09-19-2013, 06:52 PM   #3
GrantYJ
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Quote:
Originally Posted by Firefyter-Emt View Post
An somebody check this for me? I want someone with a good running 4cyl Jeep (newer YJ) to watch the idle speed. I want to know what the rpm drops to when shifting normal, and if you shift slow (double clutched). Also, if you drop it in neutral around 45mph, what does it do? How low will the idle drop. Also, at warm idle, where do you sit?

Thanks.... I am still fighting an idle problem!
Mine has idled at about 750-800 as long as I've owned it (1999). It idles slightly higher when cold but still under 1k. I couldn't tell you on shifts. I shift quickly (dude, it's a 2.5, it needs all the help it can get). As for dropping to neutral at speed, the idle isn't effected. It drops back down to the usual 750-800.
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Unread 09-19-2013, 09:26 PM   #4
Firefyter-Emt
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Yea, that's the problem I am working with... Mine is acting up on how low it will drop in netural and between shifts. It also take longer to drop at a stop like it should. I also think that the CPU may be "sticking" the IAC at two "steps" On the scanner, I see it get stuck at 24 and 8. Sometimes it will not even drop off this at idle. The IAC is new and the TB was soaked (less sensors) and washed out perfectly.I have replaced the the coolant temp and intake air temp sensors too. I have even tried spare TPS valves (and checked the one on the Jeep with the scanner) The MAP seems to be in the normal range per the scanner too. In fact, there are no codes ever, it passes emissions at 25% of the allowed limits and runs just fine. However, sometimes the idle just does not want to play nice. My syncros are on the way out, so I must double clutch... and not having the proper drop in rpm on the upshifts, means I grind the gears. Sometimes it will be up at 1500rpm at idle, once it kept that 1500 for about a mile down a mill in neutral. All the time the scanner still read the IAC at step 24. I am really starting to wonder if there is a problem with the computer itself. ANY thoughts would be great too!
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Unread 09-20-2013, 07:59 AM   #5
Que89YJ
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1989 YJ Wrangler 
 
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Did you check your switch on the power steering? The 2.5L have a switch that is used for loading from the power steering to keep the idle up. Also the alternator loading will cause the ecu to keep idle high.
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Unread 09-22-2013, 12:11 AM   #6
Firefyter-Emt
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When running at low idle, turning the wheel will kick it up... Although, back to checking basics, I may of found the problem. I had sprayed down the TB and all the vac lines to check for leaks, but I had not really sprayed down the intake to the block (yea, dumb move because I found a spot that would make the Jeep stumble when hit with carb cleaner!) So it looks like I will be pulling the intake and exhaust off to replace the gaskets (and replace a broken bolt for the exhaust) with luck, that was the problem! Or not....
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Unread 09-22-2013, 06:32 AM   #7
Que89YJ
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1989 YJ Wrangler 
 
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A high idle is usually caused by a vacuum leak. Repair it for sure. The exhaust leak will cause bad fuel economy but shouldn't effect idle. The manifold leak usually makes it run higher rpm. Keep the thread updated! It's good info if it fixes the problem.
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Unread 09-22-2013, 07:40 AM   #8
Firefyter-Emt
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I am going to give it a shot, the only problem is that on some days it idles perfect, and then it wont... In fact, the first new part I put in it (the coolant temp sensor) had to idling perfect for three weeks! Go figure, huh? But the scanner tells me that ALL the sensors are in range, so maybe that tiny leak on #3 is enough to cause it to mess up. I also am thinking that the vacuum leak would be making the MAP sensor to see a higher hg in vacuum and trying to offset for it.
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Unread 09-22-2013, 09:01 AM   #9
Que89YJ
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1989 YJ Wrangler 
 
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It sees a lower vacuum then it should because of the leak and the ECU puts more advance into the timing because of it. If it does fix it please post back. Any intake our exhaust leak will throw off the cal. and isn't doing the fuel economy or power any favors.
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Unread 11-07-2013, 04:12 PM   #10
Firefyter-Emt
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Just to finish out this thread.... I did finally get around to replacing the intake / exhaust gasket this week. I had to remove a broken stud that was broken before I bought it too. I really lucked out there because I broke a drill bit off in the stud! The stud was recessed about an 1/8" but I managed to weld a nut to the stud (and not the head!) I got very lucky there because it came right out nice and easy!

Anyway, oddly the exhaust manifold did not have a gasket at all! There was one for the intake, but it did not appear the Jeep had a one piece gasket that did both the intake and the exhaust? Very odd, and I have no idea why there was none on the exhaust, but the new one is all replace and the Jeep seems to be running great now! I did find one of the large vacuum lines were broken, that foam covered one that goes into the front of the valve cover was snapped inside the foam, but that could of been when I was removing it. It is SO NICE to have a Jeep without an exhaust leak, and I hope ALL my idle problems are fixed for good!
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