Idling not as smooth as I would like

I have a 2001XJ, 4.0 I6, AW4 and it generally runs good but the idling is not as smooth as I would like. It idles but fluctuates, and I'm guessing here from looking at the dash rpm, between 650 - 800. If I leave the engine idling stationery for several minutes you definitely here the engine change as the rpm fluctuates I'm not sure if there is any misfire but I do hear some popping noise now and again and it sounds like the exhaust might be blowing a bit as well. I have about 100200 miles on the clock I changed the plugs about a year a go and the air filter last week. As far as I know none of the sensors on the engine have ever been changed. I don't have any check engine light on. This isn't a sudden problem that just happened but a problem that has progressively got worse over time. Any ideas would be appreciated

Might not hurt to throw a can of seafoam through it. Also IAC or cat could be dirty/clogged.

Not sure about the popping noise, but a vaccum leak might cause your erratic idle...

Tried cleaning the Idle Air Controller ? Add a can of fuel injector cleaner to the next two gas fill-ups.

Thanks for the suggestions I will try them all and let you know how I get on. I haven't cleaned the IAC or checked vacuum lines.
With the seafoam I read that you can introduce it through a vacuum line on the inlet as long as it feeds all 6 cylinders. Does any of the lines feed all 6 cylinders?
If the cat is clogged, will the seafoam clean it up or will I need a new cat.
There are a lot of fuel injector cleaners out there, any experience on which ones perform best?

The cat isn't clogged (unless you have other issues).

SeaFoam, BG-44 and Techron are the best.

1. What plugs are your running? The 00-01 distributorless ignitions are supposed to get NGK V-Fires.

2. Get some BG44K and run it through the fuel system. Best fuel cleaner there is. If your local parts stores don't carry it a lot of dealerships have it, or you can get it online--eBay for one.

3. Search on for "heat soak", it is an issue on the 99+ 4.0 Jeeps, and you should be familiar with its symptoms.

4. The coil packs develop small cracks and will often fire to ground, just wanted you to be aware of that possibility.

Good luck.

With the engine cold, check the tightness of the intake manifold fasteners, along with taking heed the excellent suggestions already posted above.

With the seafoam I read that you can introduce it through a vacuum line on the inlet as long as it feeds all 6 cylinders. Does any of the lines feed all 6 cylinders?

I'll have to check the plugs not sure which ones I put in now. I will check the manifold bolts but if they need tightening they may snap they look as rusty as hell.

I remove the big hose to the brake booster and use that to suck the Seafoam in.

The Idle Air Control (IAC) is mounted on the back of the throttle body. 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 moved in, the air control passage flows more air which raises the idle speed. When the valve plunger is moved out, 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.

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)


"Gently" wiggle out the IAC from the throttle body. Gasket 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 is best for this task. 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 itself, the butterfly valve inside of the throttle body and all associated linkage as long as you have things disassembled

Reinstall IAC and check idle quality
　

gradon said:

I remove the big hose to the brake booster and use that to suck the Seafoam in.

Click to expand...

x2. but to clarify, make sure you remove the side that connects to the brake booster though and go from there haha. its much easier that way

Click on the items for an expanded "how to": http://www.seafoamsales.com/how-to-use-sea-foam-motor-treatment.html

Thanks for the advice I will try and clean the IAC at the weekend and see how it goes from there.

Thanks for the link Joe I think I will use the brake booster intake

Tryfan said:

Thanks for the link Joe I think I will use the brake booster intake

Click to expand...

Ok, just remember that all that does is clean the inside of the intake manifold and de-carbon the valves/combustion chamber, it won't clean the fuel system.

If your problem is dirty fuel system/injectors you need to do the Seafoam in the gas, per the link, or my favorite is the BG44K for cleaning the fuel system.

Good luck.

Is it easy to find BG44K? I live in PA and I have tried the usual autoparts stores nobody seems to have it. I have seen it on Ebay. Any other places?

Lots of dealerships carry it, particularly Toyota dealers.

BG shop locator: http://www.bgfindashop.com/locator/index.php

I have got some BG44K on order but in the meantime until it arrives I added a bottle of Lucas Deep Clean injector cleaner. It seemed to make an improvement for about 50 miles of driving but now after about 300 miles of driving things seem to be back to an uneven idle.
The Toyota Dealer near me can only get BG44K in a kit form and is about $50. As soon as I have the BG44K in the gas tank I will let you know how it goes.