2
Score
Brian
2.4k
Asked
Won't Idle Correctly After Attempted Repair-What Next
I have a 2000 Jeep Cherokee 4.0L ( XJ ) limited trim. It will not idle correctly. below the regular RPM or above..... i replaced the idle position sensor and had the IAC system reset by a friend who is a mechanic. ( idle sensor was to blame, to keep my question short). Everything seemed to be quite fine having done this yesterday. Even seemed to run better/stronger
Until this mourning when it would not idle at all.... until i started and held the gas down above idle speed for about 60seconds. Also does not idle at a consistent speed and occasionally idles rough.
I will be doing a tune up over the weekend since it is due, which is fairly easy with no plug wires etc just the ignition pack over the plugs.
I am not sure if this will help with my current problem since the computer should correct within reason for any ignition timing if i had bad plugs? yea?
If anyone has any ideas? let me know. If i had a bad part in the ignition system it would throw a code? and the check engine light has yet to come on and everything checked out ok just yesterday.
Edited by: David Hodson ( ) , Brian ( )
3
Score
oldturkey0
88.1k
Answered
Accepted Answer
Also make sure that you check for vacuum leaks. Mist the engine compartment with some WD40 around the vacuum lines and see if the RPM increases, if so you know you have a leak. The other thing to look for is the Throttle Position Sensor (it is located right next to the IAC in the throttle body). When it goes bad it will think the throttle plate is either to closed or to open. Of course, a bad (or going bad) fuel pump can give you the same symptoms as well.
Edited by: oldturkey03 ( )
thank you for the suggestion, if you have a link for the vacuum system for my model year please post it, it would be appreciated.. I have not been able to find this info via google, ( never fixed or looked at the vacuum system for any of the jeeps i have owned). I will have my friend check the other sensor as he has the equipment to do that and i have to go back to his shop anyway for unrelated work to be done. figuring out as much as i can before going to him is nice as he consistently helps me maintain it.
Brian, download the service manual from here http://www.keepandshare.com/doc/3247284/...
Success !! The spark plugs where in bad shape, way out of correct gap clearance or whatever the correct term is.... there was another answer posted that is gone?, which did help me as well, pointed out the spark plug and other stuff which was the problem...... SO it now idles a bit high and after warming up fairly normal, however i can figure such a minor thing later if i need to having only done this a few hrs ago....... large difference in performance as well of course. I bought a "nice" brand and quality plug this time so it should last awhile before i have to do that again...... it was fairly easy with the help of a friend to hold things and move things out of the way, coolant system hose etc..... Four 13mm bolts for the ignition pack thing....... and then all the plugs.......... put the ignition pack back on taking care to do it all of this correctly as a mistake can be quite nasty to fix. Took about an hour. Having all the correct tools acquired over time helped. I have a K&N filter which is still clean.
OK. this didn't exactly fix the problem, i should have mentioned before now....... sometimes i have to hold the gas down to start it .........while it runs better of course, once it warms up it still idles poorly / barely. Usually when cold started for the first time of the day it idles a bit high but normal, once it gets to normal operating temp driving with both feet again..... I have read online about cleaning out the throttle body and a weak battery (my battery is old and weak). I have been looking around for a solution and before taking the throttle body off and cleaning it thought i would ask for more ideas. Getting cold out and would like to get this sorted out rather then doing work that won't fix the problem. .... not sure if it matters but the coolant level is fine, the hoses on the top of the engine thou, feel too soft as if not enough pressure or liquid is present. I never did check for vacuum leaks since the problem is not constant and i don't know where the vacuum lines are.
1
Score
Answered
Another thing to check, if your truck has it, is your IAC (idle air controller). My truck actually decided to spring the same problem you're having (though I have an engine light on). It was running super rough (I could even feel a cylinder misfiring) and didn't like starting. I swapped the plugs and used fuel system cleaner and it runs almost perfect now. It just doesnt like idling when cold. (Sound somewhat similar to yours?)
I've been told that the IAC can be the cause of this. If the truck runs fine except for your idle, check the IAC...that's my next step!
Thank you for the posting,I replaced the IAC sensor it was one of the first things i did, however it was a used one, i know a bit odd using a previously used IAC sensor, however it came with several expensive parts I needed for very cheap locally ( these other parts work fine). After installing the sensor friend of mine reset the IAC system with his fancy computer thing, it ran fine for the rest of the day then back to problems ( this is before the tune up above i thought fixed the problem without waiting more then a day to make sure)....... i can go ahead and oder a new IAC sensor, just not convinced that is the problem... ( since the same problem exists just a bit different now)....... As far as i know the diagnostic machine was not able to increase RPM's which lead to the diagnosis of the IAC sensor ( This friend is very skilled figuring out problems for family members other repair places could not). He did clean out something in the throttle body awhile ago before this problem got worse.......
The computer not showing a code would make me suspicious of mechanical problems (IE not sensors or wires). A tune up is a good place to start. Replace the spark plugs, if you can clean the fuel injectors you should (Seafoam is AMAZING) and if you are so brave, I would check the valve clearances. You might consider coils too. If none of these maintenance things have been done in a while, it may clear up your problem...if nothing else, it's good maintenance! Let us know what you find.
Phillip Takahashi,