Running rough

I have a 2001 jeep Cherokee with all stock engine components except a k and n air cleaner. Recently the jeep has been running rough at idle, higher rpms it goes away, its very sporadic, its has 120,000 and routine maintenance has been done, plugs, cleaned the air cleaner, ect, ect.... any help would be appreciated. thanks

jesse

try cleaning the throttle body. that should take care of it

just use some carb cleaner?

Any check engine light noticed? If so, pull codes. If you are going to clean, I'd clean both the IAC (idle air control) and the throttle body; I've pasted in a procedure.

Be aware that high idle can also be indicative of a vacuum leak of some sort. How intermittent is this high idle? Does it happen only when cold, when hot or all the time?
----------------------------------------
Cleaning the IAC:
1. Remove the IAC with a torx 15 driver (2 bolts)
2. Gently wiggle out the IAC from the throttle body
3. Clean the IAC with throttle body cleaner (not carburetor cleaner ) Use cleaner, a rag and a toothbrush and or Q-Tips. Be gentle; don’t twist or pull on the pintle as it is fragile and you can damage it pretty easily
4. Also clean where the IAC seats in the throttle body with the same throttle body cleaner
5. Consider cleaning the entire throttle body itself as long as you’re at it
6. Reinstall IAC and check idle quality

check your upstream O2 sensor. Mine would run rough at idle, fine while driving. Unplugged the O2 sensor, runs fine.

I have a similar problem, seems to be when the engine is hot. Usually happens when 4wheeling, ill be driving fine, stop for a min, get back in and turn it on and it runs really rough for about 3 mins. I have to rev it a lot to get it to run normally. Then all of a sudden it will just be back to normal. Occasionally the check engine light will come on. Next time i will pull the code.

01LimitedXJ said:

I have a similar problem, seems to be when the engine is hot. Usually happens when 4wheeling, ill be driving fine, stop for a min, get back in and turn it on and it runs really rough for about 3 mins. I have to rev it a lot to get it to run normally. Then all of a sudden it will just be back to normal. Occasionally the check engine light will come on. Next time i will pull the code.

Click to expand...

You're problem is different. It's probably due to the fact that there is no fuel return line from the fuel rail on the Cheeps. The fuel sits there and percolates when it is hot and not running. So when restarted it runs like crap until the new fuel coming in cools everything down. Most vehicles have the better design of having a return line from the fuel rail.

Is there anything I can do to fix it or prevent it from happening?

01LimitedXJ said:

Is there anything I can do to fix it or prevent it from happening?

Click to expand...

insulate the injectors and fuel rail.

do a search for heat soak

Thanks!

Thanks guys, will do ill let you know if it helps

winterbeater said:

You're problem is different. It's probably due to the fact that there is no fuel return line from the fuel rail on the Cheeps. The fuel sits there and percolates when it is hot and not running. So when restarted it runs like crap until the new fuel coming in cools everything down. Most vehicles have the better design of having a return line from the fuel rail.

Click to expand...

I thought they did have a fuel return line?

01LimitedXJ said:

Is there anything I can do to fix it or prevent it from happening?

Click to expand...

Believe it or not, the Datsun B210 sedans of the late 70's or early 80's had a little fan blowing on the carburetor to keep the fuel from percolating. You could rig up a fan to blow on the fuel injector rail.

Another possibility would be to make your own fuel supply return line. Like on a Ford F150 (and most other vehicles), the pressure relief valve would be on the fuel injector rail with a return line to the gas tank.

One other possibility that MAY help would be to run $$premium fuel$$, which is less volatile than regular.