So I've spent months trying to figure out what might be causing my idling issue. Whenever I start my car it sometimes will start up just fine and then the next time I start it up it struggles to idle. Every time it struggles to idle it almost feels like the throttle door gets stuck and as soon as I put enough force on the pedal it gets up and going. I believe it might be the IAC but I want to what other people might think the issue is. I am going to start a job up in the mountains in NorCal so I'm planning on doing maintenance before I leave ie. spark plugs and fluids.
Troubleshooting an idle issue
- Thread starter JacksonH
- Start date
A dirty IAC can cause that. It can be cleaned by spraying an aerosol can of throttle body cleaner into the throttle body while the engine is running at idle rpms. Only when the engine is running at idle rpms will the cleaner get pulled into the engine through the IAC cleaning it. I'd spray at least 1/3 of the can like that. Then raise the rpms and use the rest of the cleaner to clean the inside of the TB. This method will clean the entire IAC and its orifice it fits into in the throttle body.
The engine will die each time the cleaner floods the IAC. That's ok and good, just restart the engine and do it again.
The engine will die each time the cleaner floods the IAC. That's ok and good, just restart the engine and do it again.
I cleaned a few months ago and cleaned again this week. Both times using the method you suggested and I still am having a rough idle.
Have you checked your fuel rail? Could be a failing fuel pump. I was having this same problem and it turned out my fuel pump was failing. My pressure was about 13 psi, should be about 40-45 IIRC
What ignition system does your 2000 have, a distributor or does it have the coil rail? 2000 was a transition year for the ignition system. If it has a coil rail, do you happen to know the exact brand and model # of the spark plugs? The coil rail ignition system is very fussy about its spark plugs and single-tipped platinum plugs like Autolite's AP-985 or Champion's 3034 will cause rough idle issues.
I have no clue what plugs I have. I do have a coil rail. I am not the only owner so I have no clue what the previous owners put in there or if they have even been changed. I bought 6 Autolite XP985 plugs that I plan to replace sometime next week.
I don't think it is a fuel pump since it doesn't seem to be losing fuel when my foot is on the gas pedal but it probably doesn't hurt to test it.
That's a good choice and what I'm running myself. The newer 4.0 engine's coil rail system produces a waste spark that will cause a problem if the spark plug's electrodes don't have the same material on both sides of the gap like plugs with a platinum coating on just one side of the spark plug gap.
No guarantees this is the fix but the wrong plugs definitely cause an idle problem with the coil rail ignition system. Keeping my fingers crossed it's this easy of a fix.
Rubicon88
TJ Addict
Do NOT install the autolite plugs when having trouble.
You need to get back to ground zero. Ground zero meaning OEM recommended parts.
The autolite plug has worked for some but it has also caused trouble. I own a repair facility. Seen it myself changing back to the oem plug.
This very forum has its share of Jeep issues with symptoms that got better changing to the OEM plug....which is NGK ZFR5N.
You very well might have other issues but the key is doing all you can to eliminate possible trouble issues by getting to ground zero...then re-evaluate.
The only way youll really notice if your fuel pump is going bad besides the rough idle is loss of power when driving. It gets progressivly worse over time though so its hard to tell unless youve delt with it before. You should be able to get a fuel pressure check gauge at your local autoparts store
The correct model Autolite plugs work perfectly well, many of here run them and recommend them on a regular basis. They function as well as Champion, NGK, etc. and are a very high quality spark plug. If you want to argue the point, go right ahead but I'm definitely not going to waste my time responding.
I'm not too worried about the spark plugs and going with OEM. This is my first car and I have a job that pays well enough that if I just have to go with OEM plugs I'm not gonna cry about it.
Rubicon88
TJ Addict
What is there to respond to? I said they work for some and others have issues with them.
Just to be clear there are other Jeep's in the world besides yours.
That said they are NOT the OEM plug and people have HAD issues with them. When dealing with an issue the very first thing that should be done is get the pertinent parts...in this case plugs...to the OEM recommended version.
The Autolite plug MIGHT work fine.
The NGK WILL work fine and dealing with a problem I'd be inclined to eliminate possible problems to track it down.
That's just me though.
Rubicon88
TJ Addict
I change all 6 of my plug. The plug I took out looked pretty new and was gapped at. 035 but plugs 4 and 5 had a little bit of carbon on them and plug 6 had some rust on the ceramic. The previous brand was Denso.