FastDemise Posted July 2, 2015 Share Posted July 2, 2015 Cleaned throttle body in ultra sonic cleaner so it's spotless. Went thru and adjusted the TPS spot on. Sensor tested good with smooth transition in voltage from closed to WOT. The P.O. was adjusting the butterfly valve as 'idle control'. I have the butterfly stop set so it just touches when it closes and no visible light passes thru. What can I look at next? http://i.imgur.com/YB5dg6c.jpg Link to comment Share on other sites More sharing options...
Jeep Driver Posted July 2, 2015 Share Posted July 2, 2015 Could be your idle air control. I also have low idle, in my case I have one cylinder with low compression that is evident at idle....and........I suspect my O2 needs to be replaced (burns rich). I have a new engine waiting so I'll live with it until the new install. Link to comment Share on other sites More sharing options...
FastDemise Posted July 2, 2015 Author Share Posted July 2, 2015 I can pull a vacuum line and listen to the rpms rise to 1k then adjusts itself to a nice 500rpms automatically. But if I replug the vacuum line to quick the engine will stall. I have to slowly reconnect to let the computer catch up. It seems the IAC works but much slower then my XJ which responds very quickly and has no trouble adjusting. Jeep Driver, good luck on completing ur build. It's really impressive. Link to comment Share on other sites More sharing options...
cruiser54 Posted July 3, 2015 Share Posted July 3, 2015 Welcome. What year is your Jeep? How did you adjust the TPS? Have you seen my Tips in the link below? 1 through 5 should be completed first. Except 2 if you have an 89 or later. Tip 8 covers TPS setting and Tip 14 covers throttle body adjustment restoring. YOu could also have a bad O2 sensor as previously mentioned. Link to comment Share on other sites More sharing options...
FastDemise Posted July 4, 2015 Author Share Posted July 4, 2015 Welcome. What year is your Jeep? How did you adjust the TPS? Have you seen my Tips in the link below? 1 through 5 should be completed first. Except 2 if you have an 89 or later. Tip 8 covers TPS setting and Tip 14 covers throttle body adjustment restoring. YOu could also have a bad O2 sensor as previously mentioned. Oh yes, I already have your list printed out and following up on all my grounds as we speak. I followed #8 & #14 when I adjusted the throttle body. I'll check the resistance of my MAP and temp sensors then follow-up with the O2 sensor. Will update with results. Link to comment Share on other sites More sharing options...
FastDemise Posted July 15, 2015 Author Share Posted July 15, 2015 So I'm on hold until I can get a new manifold gasket. Seems checking manifold for tight bolts revealed all lower bolts were loose enough to move with fingers and rear most bolt in exhaust was just gone. So took everything off to clean up carbon buildup (last tank I ran only 12mpg) then I can replace the old gasket. Got a new coolant sensor, o2 sensor, and replace quick disconnect fuel orings in fuel rail. Will see how long it takes to piece back together in my free time and if my low idle problems ago away. Link to comment Share on other sites More sharing options...
cruiser54 Posted July 16, 2015 Share Posted July 16, 2015 2 more things to do. At idle, spray around where the MAP sensor tube connects to the throttle body. Do a fuel pressure test and make sure the pressure is 39 with the vac hose disconnected from the fuel pressure regulator and 31 with it connected. If you don't have access to a gauge, there is a way to test what we're looking for. Do the pressure deal last. Link to comment Share on other sites More sharing options...
FastDemise Posted August 3, 2015 Author Share Posted August 3, 2015 I already tested the fuel regulator a few weeks back and it was 30 with vacuum connected and 40 when it was disconnected. I will grab a can and start looking for a vacuum leak. I replaced the manifold gasket and trucks is running better but now it's rock solid at around 200-250rpms. Starts and runs great. Just idles real low and you can hear the idle slowly waver higher and lower rhythmically. It runs dependable now I just gotta start on my wiring upgrades and find any pesky vacuum leaks. Thanks for all y'all help so far. Link to comment Share on other sites More sharing options...
FastDemise Posted September 25, 2015 Author Share Posted September 25, 2015 Update TimeI have grabbed a bunch of spare sensors from the junkyard, Replaced the alternator as I noticed my voltage was fluctuating and now I get a solid voltage output. I've gone as far as unhooking the vacuum hose from the rear PCV and listened as the rpm's rose then returned back to exactly like the photo shows in my first post. I reconnected to hose and then tried the Uncle Bob approach. This also yielded no result as the truck just readjusts the idle to stay low. Seems my IAC is working beautifully based on how it responds to vacuum leaks and forcing the throttle stop open. Now the question is what sensor is giving the ECU bad info that is causing it to maintain my low idle. I have a knock sensor unhooked and have been driving it last few days without connected. That is where I am at now. Will keep reading up on others online that have had low idle and all the different fixes people have come up with. Link to comment Share on other sites More sharing options...
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