UPDATE: HIGH IDLING IS A VACCUUM LEAK ISSUE GONNA BE TRACKING THIS DOWN TO FIX THIS. my non expert video of changing your IAC valve. this can be done when cleaning your valve has not fixed your idle issue.
I had a tight idler pully that was going out that helped make my idle high, also air conditioner was tightening up inside, causing drag. My throttle position sensor was bad, which mostly finished fixing it. Also, jeeps wire harnesses tend to be cut to pieces near engine bolts, especially in back. Your largest vacuum leak is probably in the back where gas tank epa canisters are hooked up behind left fender for laredos
I had the same issue with my 1999 cherokee xj. The idle would rise and fall like I was pumping the gas pedel. Ended up after checking for vacum leaks and changing all the sensors on my throttle body, the problem was my upstream o2 sensor.
Lots of comments on the idle speed. Based on my XJ which is a 96 4.0 it runs at 800 rpm. This is the IDLE mode. On a "96" model the powertrain control module (PCM) gets it's input from the A/C, Battery Voltage, Crankshaft position sensor, engine coolant sensor, intake manifold sensor, Manifold absolute pressure(MAP), Throttle position sensor(TPS), Camshaft position sensor in distributor, gear switch(automatic's), Oxygen sensor. The PCM takes all these signals to run it at 800 rpm. If something is bad the computer is going to run at a higher speed or not at all.
I want to pick your brain Sir. I deliver mail out of a '96, and am having issues with idle jumping to about 1100-1200 when I put it in park. Sometimes I can rev it, and it will settle to the 800. Care to take me under your wing? So tired of mechanics guessing.
@@belamtn We could try. I just had a problem with my Jeep when I would go over speed bump or if I made a quick stop my engine would shut down. Drove me nuts the only code was for a idle air valve. Finally found the wire that goes to the distributor was bad. The valve was okay. The first thing to look at is all the vac hoses make sure you have NO LEAKS, go to a auto parts store and check your battery and alternator. Is this with the A/C on or off when it happens?
@@jeep146 OK, here goes......The AC has been removed, and the switch for it is never on. Any chance the PCM is pissed at getting no signal from there? Can I block/fake it? Some other tidbits about my little fella: New engine installed about 2000 miles ago. Battery and alternator are new. I'll have the VAC checked. I have a persistent code P0420, Cat sensor (downstream), and CEL is on. I replaced the CAT last March and it's the second sensor installed. I have NOT confirmed my CAT has failed this time, but it is certainly the suspect given the sensor is new. I am hoping to try the spacer trick on it Sunday to fool the computer and get the CEL off. No OEM CATs available I am told, and I hear nothing good about aftermarket ones....so WTF. I installed a new OEM TPS this Summer, also the MAP and distributor are new. I KNOW NOTHING about the gear switch you mentioned above, or the intake manifold sensor. What say you? ANd sorry if I sound like a dumbass, I'm really not one.
@@belamtn No problem, If the a/c was removed and you didn't have problems we can move on. The new engine part is another reason to make sure all your vac lines are tight and in the right place. Be careful with some of the videos some will mask a problem not fix a problem. Your CAT should be good unless it was bad to begin with. The 72 code/P0420 looks at your O2 sensors, your Cat may not be bad just your sensors. To test the Cat I haven't done it in awhile but you remove the sensors and read the pressure and also look at the temp coming in and going out. This is very important to fix these problems. The computer needs to know how rich or how lean to set the engine. Everything is calculated in the computer when people try to fool it the computer can never do its job right. The O2 sensors can get dirty they do have videos on how to clean them before replacing them, just clear the fault codes when you do. If your old engine was burning oil that could mess the sensors up to. The TPS usually screws up when your driving, my MAP just made it run like crap all the time. Check the engine grounds this is very common on jeeps to have bad grounds to the engine block. You really need to fix that O2 problem. Does the gauge read correct temp when it is warmed up? The Gear shift is used when starting, not your problem. If you have a meter you can check the intake manifold sensor. it sits near the throttle body on the manifold it should read less than1340 ohms when warm. Also beware some people adjust the throttle set screw to lower the RPM never do this. If the old engine ran okay but the new one runs fast check all the connections and the hoses.
Erase the ecu by disconnecting the positive battery terminal and grounding it to the ac pump for 30 seconds then reconnect it, this will allow the ecu to relearn the new sensors and run better.
I've found that the jeep inline 6 really only works well with mopar OEM tps.Most after market throttle position sensors use inferior parts.If you have a shop level scanner,you will see in most cases cheap sensors the values will be all over the place
Thanks for the info. This jeep hasnt really moved. Its been awhile since this happens but i might look at it soon now that i tackled a list long of upgrades to my other jeep. Will post a video about this too if i figure it out. Thanks!
Exactly, I've ran through 500ish bucks in Aftermarket parts. Crank sensor, IAC, VSS, etc. None of them worked right but as soon as I put the OEM part in they work perfectly.
I hope you still have your vintage Jeep. I have a vintage 97 Wrangler TJ I bought new back in late 1996. She has 415,000 miles on the odometer. My ECM just went bad and I had to jump 12 volts to the fuel pump and the injectors. She is running rough when cold. This is the first timed she has ever fallen ill. Never part with your vintage Jeep.
Have the exact same problem after TB cleaning and 4 hole 24lb injectors. Only way i was able to fix the idle was to adjust the idle screw from the bottom side of the TB
Hi. I put 4 holes in, now I'm running rich with Codes po172, po175 oxygen sensors. I replaced both up streams, no change. Having a rough idle now too that I can't find. IAC was fine Before new injectors. Thinking of going back to a one hole? Any suggestions?
You do not need to pull the throttle body to doan IAC swap! Also, his RPM's were 1000 after he swapped the IAC; this is NOT idle speed. At this RPM the engine is running, not idling, and the IAC serves NO PURPOSE! My guess is he has a vacuum leak or a misadjusted idle speed screw on the underside of the throttle body!
I had an issue with my YJ for years with high idle when ambient temperature started to hit mid 80's. 1100-1200 RPM when 80-ish outside, to 1800RPM if it was 90+ outside. Found a mechanic that figured out the computer wasn't relearning the new IAC Valve after replacement. He was able to reprogram it to work correctly. SO happy to have it working correctly again! And, that idle in the video is too high, should be like 700-800RPM.
@Nick Gur If the T/B has not been cleaned in a long time (or *ever*) it is worth removing it to *clean thoroughly*.. Especially the IAC housing!. I remove the IAC, TPS and MAP (if yours is located on the T/B) also remove the IAC *housing*, and *clean everything* Unnecessary?, No, not to me. :)
I've seen the needle more drastically like this before, I'd look for a leak in the exaust. Stick your hand on the back on the muffler and check the pressure. I also agree with the other poster about the idle. I've got the sam issue but I'm at 700 right now, I'm just holding off until after winter, I'm fixing the radiator stuck on while starting, not kicking off.
My Jeep was in a flood for a day under water up to dash, I got it “running” but it idle really rough and shut off if you don’t give it some gas. Would this be my problem ?
Ozzy Stuckman my problem was the tank still had some water in it, so I cleaned it out really good and changed the filter as well. Worked fine after that. I drained my oil 2-4 times, took plugs out turned over a couple times till all the water shot out, put new plugs in. That’s all the stuff I did.
Oof, im not a mechanic, but I got a jeep myself, and you may actually be having electrical problems if you've done everything right to get water out of the engine
@@mikeirl3565 hello, I got it running fine but I sold it before I ran into the bad electrical problems if they ever do happen, the guy knew it was in the flood defiantly made sure he knew haha
@@BradleyBeeksAdventures Good deal bro, it'll probably be fine, just takes a little more damage control know-how then we know how to do lmao, I wish that dude good luck, electrical is always "fun"
It won’t start, at least for me I swapped in a new alternator and starter along with the sensor and was about to unbolt the starter when I decided to flip the sensor and bingo.. power, initially I had positioned it so the wire opening to the sensor would point down so as not to allow water in but the Jeep wants it ass up for whatever reason
You may have already fixed your jeep Cherokee but here's what happened to me. I have a1993 Cherokee and it would stumble and have a rough idle. The throttle body was very dirty with carbon so I removed it and cleaned it with carburetor and choke cleaner. Removed the idle air valve and cleaned it to. Reinstalled everything and then the idle was at 1200 rpm. No vacuum leaks. I had to adjust a small bolt on the throttle body leaver butterfly to lower the rpm's to 800 with a warm engine. But it still would stumble and cut out until the engine warmed up. But the idle was performing perfect. So I checked the engine codes in the computer by counting the blinking dash light and it said I needed a oxygen sensor. Installed a new one and that fixed the stumble. So now it runs great. Oh it's got 348,000 miles. Good luck.
@@randybarnes8454 Thank-you very much. I fixed it a few months back. I cleaned my throttle body as well and put in a new iac valve. Been working so far. Damn that's a shit load of miles lol. Mine is in the high 200s
I just had something happen now, I drove my xj about 40min , parked, set the xj on park and idle was at 1000, I turned it off and turned it back on and it jumped to 3500. Never experienced this before, any ideas?
After swapping the IAC, drive the vehicle five miles or so at 45 mph to allow the brain to reset the idle to norm.....serious, it's in the installation instructions. Dig 'em outta the trash and see......lol.
Nothing, internally the valve is the same, the main, and the really only problem you'd have, is going to be that you have to twist your wiring harness around to reconnect it, which on an old jeep with brittle wires can be a big no no
Hey chill bro, idk if you own a 90s-2000s Jeep or not, but out here we cut corners, and it's not that we're all cheap, its cuz these 4.0's can just take it, they're not Priuses, I didn't replace my gasket ether when I cleaned my throttle body
I really hope you are still with your girlfriend. She is automatically sexy because she drives a Jeep. Please forgive me noting the obvious. She can not help but to be sexy when she'd drives a vintage Jeep. Love the cat.
Yup everyone says get Mopar sensors or else the World will End 😆 but I've had great luck with Standard brand sensors and even that's their cheaper range. Haven't tried the Amazon sensors yet but they are dirt cheap & the feedback seems ok so maywell do
I took the throttle body off, and there is no gasket. Does that matter, because it always ran good up till now. It smokes bad and runs rough until it warms up, and then it's good. I hate to replace parts and it doesn't fix it.
Jeffro you should have a gasket, yes. You sure it didn’t stick to the bottom of the throttle body? As far as running rough til it warms up, that sounds like it could be your O2 sensor. The one before the catalytic converter
@@victorjramirez1948 Hey buddy listen, buy that IAC motor, remove your throttle body, clean it and get all the carbon deposits off. Brake clean, or throttle body cleaner, and a small wire brush works. It doesn't have to be perfect. But the major thing that fixed it for me was effectively cleaning the housing that the IAC screws into. And if your screws strip out like mine did, just find another screw that threads in tight. My jeep runs perfect now, no dash lights. I am, by the way, a professional mechanic. Let me know if you have issues.
@@luketrochinski3954 YOU COULD HELP ME, I HAVE A ZJ ORVIS EDITION 95 4.0, WHEN IT IS IN DRIVE SHUT OFF, CHANGE THE TEMPERATURE SENSOR AND NOW I REMAIN IN 1000RPM DO NOT BECAUSE, ONLY CHANGE THE TEMPERATURE SENSOR NOW WHEN YOU WANT TO TURN OFF ONLY ONLY VERY FOLLOWED ONLY AS 2 OR 3 TIMES EVERY 10 MINUTES ONLY WHEN IT IS IN DRIVE, IN NEUTRAL DOESN'T, DOES NOT LIGHT THE CHECK ENGINE, WHAT CAN IT BE?
@@luketrochinski3954 YOU COULD HELP ME, I HAVE A ZJ ORVIS EDITION 95 4.0, WHEN IT IS IN DRIVE SHUT OFF, CHANGE THE TEMPERATURE SENSOR AND NOW I REMAIN IN 1000RPM DO NOT BECAUSE, ONLY CHANGE THE TEMPERATURE SENSOR NOW WHEN YOU WANT TO TURN OFF ONLY ONLY VERY FOLLOWED ONLY AS 2 OR 3 TIMES EVERY 10 MINUTES ONLY WHEN IT IS IN DRIVE, IN NEUTRAL DOESN'T, DOES NOT LIGHT THE CHECK ENGINE, WHAT CAN IT BE?