aprildaisy Posted April 23, 2018 Share Posted April 23, 2018 Hi, I've got a problem I'm hoping someone here can point me to a solution for. I've got a '91 Comanche that tries to die when I press the clutch to decelerate. Sometimes it doesn't, sometimes it does. If I press the gas petal to give it just a little juice when I do press the clutch to decelerate, it won't die and will idle just fine. So, that's my main way of working around this. However, I'd love a real solution. Thanks a million. Link to comment Share on other sites More sharing options...
Pete M Posted April 24, 2018 Share Posted April 24, 2018 how well does it idle/rev/idle while just sitting in the driveway? Link to comment Share on other sites More sharing options...
cruiser54 Posted April 24, 2018 Share Posted April 24, 2018 Ever clean your throttle body and IAC? http://cruiser54.com/?p=60 Link to comment Share on other sites More sharing options...
aprildaisy Posted April 25, 2018 Author Share Posted April 25, 2018 Sorry, I didn't get notified of responses. I'll check back better. Pete, it idles just fine when started/sitting. cruiser, I have no idea, but I could mention that to my husband and son. They work on everything. I just inquire as needed when stumped, like this. lol Link to comment Share on other sites More sharing options...
Ωhm Posted April 25, 2018 Share Posted April 25, 2018 Flame-out on decel, my guess is spark plugs, unless, of course, they had just been changed recently. Link to comment Share on other sites More sharing options...
aprildaisy Posted April 26, 2018 Author Share Posted April 26, 2018 Hubby just said my IAC is one off of something else in the yard and that could be worn. I'm looking into it. Link to comment Share on other sites More sharing options...
ParadiseMJ Posted April 26, 2018 Share Posted April 26, 2018 2 hours ago, aprildaisy said: ... IAC is one off of something else in the yard and that could be worn... If it's the IAC, I'm pretty sure the IAC can't be "one off". More likely dirty. Take it out, clean it with carb cleaner...be gentle with it when handling the pintle...(tip)... so's not to damage it. Link to comment Share on other sites More sharing options...
aprildaisy Posted April 26, 2018 Author Share Posted April 26, 2018 A tune up was done recently, so that's not it. Link to comment Share on other sites More sharing options...
aprildaisy Posted April 30, 2018 Author Share Posted April 30, 2018 Well, just replaced the IAC and, from the looks of the one taken out, it was definitely a factor! I haven't driven it yet, but both my Son and Husband say it runs and sounds better just idling. Thank you so much for helping direct me there!!! On 4/23/2018 at 11:45 PM, cruiser54 said: Ever clean your throttle body and IAC? http://cruiser54.com/?p=60 Link to comment Share on other sites More sharing options...
Ωhm Posted April 30, 2018 Share Posted April 30, 2018 Link to comment Share on other sites More sharing options...
Pete M Posted May 1, 2018 Share Posted May 1, 2018 fingers crossed!! Link to comment Share on other sites More sharing options...
ParadiseMJ Posted May 1, 2018 Share Posted May 1, 2018 4 hours ago, aprildaisy said: Well, just replaced the IAC and, from the looks of the one taken out, it was definitely a factor! I haven't driven it yet, but both my Son and Husband say it runs and sounds better just idling. Thank you so much for helping direct me there!!! That's great. After reading this I removed my IAC on Saturday, when I was tinkering, mostly out of curiosity. It had some stuff on it that I cleaned off and scuffed it with some fine sandpaper. It immediately idled more smoothly and went from an chronically wonky 500-700 RPM. Now it's rock solid at 750. Link to comment Share on other sites More sharing options...
cruiser54 Posted May 3, 2018 Share Posted May 3, 2018 Maintenance.....Gotta love it. Link to comment Share on other sites More sharing options...
aprildaisy Posted May 8, 2018 Author Share Posted May 8, 2018 Well...while changing that part helped it along, it didn't fix the problem. Sigh. lol Paradise, glad this helped you!! On 4/30/2018 at 10:55 PM, ParadiseMJ said: That's great. After reading this I removed my IAC on Saturday, when I was tinkering, mostly out of curiosity. It had some stuff on it that I cleaned off and scuffed it with some fine sandpaper. It immediately idled more smoothly and went from an chronically wonky 500-700 RPM. Now it's rock solid at 750. Link to comment Share on other sites More sharing options...
aprildaisy Posted September 5, 2018 Author Share Posted September 5, 2018 I still haven't found a solution for this. Maybe there's a new member or some new idea one can give me. Either way, thanks for being here. :) Link to comment Share on other sites More sharing options...
HOrnbrod Posted September 5, 2018 Share Posted September 5, 2018 You have a 91. Have you tried checking for fault codes? Link to comment Share on other sites More sharing options...
Minuit Posted September 5, 2018 Share Posted September 5, 2018 A cracked vacuum line to the MAP sensor did a very similar thing on my '89. Immediately fixed by replacing that line. Link to comment Share on other sites More sharing options...
omega_rugal Posted September 5, 2018 Share Posted September 5, 2018 ONLY when you press the clutch? is there a sharp rpm drop while shifting? with engine hot and idling and transmission in neutral, press the clutch... see if RPMs drop, if so the throwout bearing or internal cylinder is bad, normally when you press the clutch the THB/IC turn with the pressure plate, if the bearing is damaged or stuck it will bring the rpms down enough to stall it... Link to comment Share on other sites More sharing options...
ParadiseMJ Posted September 6, 2018 Share Posted September 6, 2018 So, do you always press in the clutch just to decelerate? Have you tried just letting up on the gas, braking, downshifting and pushing in the clutch when you stop? I may be wrong but that's how I've always driven a stick. Just sayin' Link to comment Share on other sites More sharing options...
cruiser54 Posted September 6, 2018 Share Posted September 6, 2018 clean the throttle body..................... Originally by TJWalker of CherokeeForum & JeepForum The Idle Air Control (IAC) is mounted on the back of the throttle body (front for ’87-’90). The valve controls the idle speed of the engine by controlling the amount of air flowing through the air control passage. It consists of a stepper motor that moves a pintle shaped plunger in and out of the air control passage. When the valve plunger is retracted, the air control passage flows more air which raises the idle speed. When the valve plunger is extended, the air control passage flows less air which lowers the idle speed. Over time and miles, the IAC can get carboned up which can have an adverse affect on idle quality. Cleaning the IAC may restore proper function and is an easy procedure to perform and good preventive maintenance so it is never a bad idea. This should be part of a normal tune-up procedure and whenever idle/stalling issues are present. CLEANING THE JEEP 4.0 IDLE AIR CONTROL Remove the air filter cover, associated hoses and the rubber boot that goes from the air filter cover to the throttle body. Remove the IAC with a Torx driver (2 bolts; one can be kind of hard to get to). On ’91 and later, it may be easier to just remove the whole throttle body. Be sure to use a new throttle body to manifold gasket when reinstalling. “Gently” wiggle out the IAC from the throttle body. Gasket/O-ring on the IAC can be re-used if it is not damaged Clean the IAC with a spray can of throttle body cleaner; inexpensive and available at any place that sells auto parts. Throttle body cleaner is recommended rather than carburetor cleaner as it is less harsh, safe for throttle body coatings and oxygen sensors. Use cleaner, a rag and a toothbrush and or Q-Tips. Be gentle; don’t twist or pull on the pintle that protrudes from the IAC as it is fragile and you could damage it. Thoroughly spray clean and flush where the IAC seats in the throttle body with the same spray cleaner. It is also a good idea to clean the entire throttle body bore itself, the butterfly valve inside of the throttle body and it’s edges, and all associated linkage as long as you have things disassembled. Link to comment Share on other sites More sharing options...
omega_rugal Posted September 9, 2018 Share Posted September 9, 2018 wait, what does the IAC has to do with it? if it was dirty cleaning it will help smoothing idling rpms, whe you press the clutch you are releasing the engine from the transmission, is supposed to run free, why woudl the rpms drop? a dirty IAC will give overall low rpms at idle... Link to comment Share on other sites More sharing options...
gogmorgo Posted September 9, 2018 Share Posted September 9, 2018 Assuming normal manual transmission operation, when you push in the clutch pedal, you also have released the throttle. The engine returns to idle, so you need the IAC to keep the engine running properly. If it's sticking shut, or otherwise not opening far enough, the engine will die. Link to comment Share on other sites More sharing options...
Dixie Posted September 9, 2018 Share Posted September 9, 2018 On 9/5/2018 at 8:56 PM, ParadiseMJ said: So, do you always press in the clutch just to decelerate? Have you tried just letting up on the gas, braking, downshifting and pushing in the clutch when you stop? I may be wrong but that's how I've always driven a stick. Just sayin' That’s where my mind went. Or I just pop it in neutral Link to comment Share on other sites More sharing options...
Ωhm Posted September 10, 2018 Share Posted September 10, 2018 On 4/25/2018 at 7:59 PM, Ωhm said: Flame-out on decel, my guess is spark plugs, unless, of course, they had just been changed recently. On 4/26/2018 at 9:06 AM, aprildaisy said: A tune up was done recently, so that's not it. What were the spark plugs gap set to? Not sure exactly what the specs calls for. Anyone? Link to comment Share on other sites More sharing options...
HOrnbrod Posted September 10, 2018 Share Posted September 10, 2018 29 minutes ago, Ωhm said: What were the spark plugs gap set to? Not sure exactly what the specs calls for. Anyone? .035 Link to comment Share on other sites More sharing options...
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