mgardster Posted July 23, 2012 Share Posted July 23, 2012 I'm new to this forum, but I posted the same question on another forum and didn't get any good answers. I have an 87 2.5 with 4sp, no A/C, no P/S, and everything is stock. When I start the engine, the rpms are normal, but when I give it some gas, the rpms stay high after taking my foot off the gas. If I blip the accelerator, the rpms drop to normal and stay there until I start to give it a little gas again. This is constant, every time I drive it. I've checked for vac leaks and can't find any. It's not a sticking cable. The engine has 250K miles and I've owned it for 17 years. The engine has never been opened up and the ox sensor is the same one for the last 17 years. Any Ideas? Link to comment Share on other sites More sharing options...
jimoshel Posted July 23, 2012 Share Posted July 23, 2012 There's something in the throttle body or linkage that's sticking. Remove the linkage at the throttle body. Now start it and work the throttle by hand. See what it does. Spray everything good with PB. If you know it's not the linkage then check throttle plate. Link to comment Share on other sites More sharing options...
mgardster Posted July 23, 2012 Author Share Posted July 23, 2012 I'll try that in the morning, but so far, I haven't noticed anything sticking open. Just the rpms up. I've played with this thing for some time now and it's not obvious. I'll check it again. C Link to comment Share on other sites More sharing options...
cruiser54 Posted July 23, 2012 Share Posted July 23, 2012 Isn't there an ISC motor that the throttle linkage uses as a stop? ISC=Idle speed control. Link to comment Share on other sites More sharing options...
Zenobian_84 Posted July 23, 2012 Share Posted July 23, 2012 Isn't there an ISC motor that the throttle linkage uses as a stop? ISC=Idle speed control. Yes, there is. It sounds like the ISC is on it's way out, because it sounds like the exact same thing that mine was doing before it took a nosedive. :fs1: Had the same problem a while back; high idle after startup that wouldn't go back down to the 800-1200 rpm range. Checked the throttle body and cleaned it, didn't help anything. Checked vacuum lines, couldn't find any that were bad or leaking. It probably wouldn't hurt to replace the O2 sensor as well; it helps remedy part of the problem of a high idle on the 2.5. Link to comment Share on other sites More sharing options...
mgardster Posted July 23, 2012 Author Share Posted July 23, 2012 Here's what I just found out. After driving it and letting it warm up, I pulled back in to the driveway and jumped out while it was still at high idle. I grabbed the throttle and pushed it back to the rest position and the idle went down to normal. I guess the ISC motor is the black plastic thing with the throttle stop on the end where the throttle is suppose to rest at idle? If that's the case, the ISC is not pushing the throttle back, it's the shaft that's not coming back to rest. Maybe it's dirty and it's sticking. You would think the big spring on the cable would pull it back to the idle rest. Is it much trouble to clean the shaft? You guys are a lot of help. Thanks!! Link to comment Share on other sites More sharing options...
cruiser54 Posted July 23, 2012 Share Posted July 23, 2012 I think yo uhave to replace them shen they stick like that. Check it out. Link to comment Share on other sites More sharing options...
Zenobian_84 Posted July 23, 2012 Share Posted July 23, 2012 Here's what I just found out. After driving it and letting it warm up, I pulled back in to the driveway and jumped out while it was still at high idle. I grabbed the throttle and pushed it back to the rest position and the idle went down to normal. I guess the ISC motor is the black plastic thing with the throttle stop on the end where the throttle is suppose to rest at idle? If that's the case, the ISC is not pushing the throttle back, it's the shaft that's not coming back to rest. Maybe it's dirty and it's sticking. You would think the big spring on the cable would pull it back to the idle rest.Is it much trouble to clean the shaft? You guys are a lot of help. Thanks!! Yup. ISC is on it's way out. If it looks like this then that's the problem. As qouted by Don almost 3 years ago from my searching a month ago for a New ISC (2.5 Litre) - Don't know whether or not yours is a 4 banger or 6 cylinder. Somebody can probably chime in with the P/N for a 6 cylinder. I also don't know if there is a difference between the I6 and I4 ISC. :dunno: Jeep p/n 83502375, Aftermarket manufacturers p/n 17079129. Fits 100s of Chrysler and GM vehicles. See RIGHT HERE Link to comment Share on other sites More sharing options...
mgardster Posted July 24, 2012 Author Share Posted July 24, 2012 Nice pic, but I don't think that's the problem. Mine is not sticking out like yours in the picture. When I push the throttle back to idle, it just touches the ISC motor, so that's not what is keeping the rpms up. While I was outside trying to clean the shaft, I noticed there is only one spring on the throttle (other than the coiled one on the shaft) and it pulls with the cable in the same direction as if to help with pushing the gas pedal. Is there suppose to be another spring that pulls the throttle back to idle, opposite of the other spring? I would take a picture, but right now I'm not home. (it's a four, not a six) Link to comment Share on other sites More sharing options...
cruiser54 Posted July 24, 2012 Share Posted July 24, 2012 4 bangers have ISC, Idle Speed Controllers and 6 bangers have IACs, Idle Air Controllers. They work completely different from one another. Link to comment Share on other sites More sharing options...
mgardster Posted July 31, 2012 Author Share Posted July 31, 2012 A simple return spring was all it took... Thanks for all the suggestions. C Link to comment Share on other sites More sharing options...
88whitemanche Posted August 15, 2012 Share Posted August 15, 2012 Hey red rocker.... How much was the idle speed control sender? I'm having the same problem you had with it idle Link to comment Share on other sites More sharing options...
Zenobian_84 Posted August 15, 2012 Share Posted August 15, 2012 Hey red rocker.... How much was the idle speed control sender? I'm having the same problem you had with it idle $99 for a regular replacement through Rock Auto IIRC. I got a GM one at a discount for $72 shipped. Has been working great since I replaced it. Link to comment Share on other sites More sharing options...
88whitemanche Posted August 16, 2012 Share Posted August 16, 2012 Ok awesome...well that has to wait now lOl my alternator crapped out on me time to buy a high power one but sweet deal on the discount Link to comment Share on other sites More sharing options...
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