Cleaning the throttle body gone bad

[scoobyxj]

So, would a bad/ dirty IAC cause it to idle very low too? My 2001 Cherokee stalls at intersections when idiling. I'm going to try to pull off the IAC and clean it up a bit tonight. Any recommended carb cleaner? Any tricks involved?

Unless you know how to check them it's just a guess. One way to tell if it is the IAC is (if it will run at all without holding your foot on the gas a bit) if you can hear the idle increase when the A/C compressor cycles. If does then I would say the TPS. If it just seems like it wants to stall when you let you foot off the gas (like when you come to a stop, or was reving the moter up a bit) then I would gess the IAC is at least gummed up, and sticking if not bad.

 

[Neil]

Great info, thanks. How do I check for vacuum leaks? I'm pretty new with all of this. Do you think it's the IAC?

It could be the IAC. You'll find that most all carb cleaners contain Methyl Alcohol which is not good for plastic. Throttle body cleaners sometimes do not. The amount of time that the plastic pieces are exposed to the alcohol is minimal (you get much more alcohol contact by running Arco gas or "oxygenated fuel") So soak less and clean more. Checking for vacuum leaks is a pain. First look for the obvious like disconnected hoses. Then start moving hoses around. listen for rushing air or a very high pitch whistle and look for cracks, breakage or loose fitting connections. Also check the intake for loose mounting bolts and loose TB bolts. Some might suggest spraying W-D40 or carb cleaner on the hoses and listening for changes in the idle. I don't like spraying flammable liquids on a hot engine. (Now I'm not saying that I have never done it, I'm just saying that I don't like to.) I think that you are on the right track by looking at the IAC. I usually start looking at the cheapest and easiest fix first and move on to the consecutively more expensive and more difficult fixes. I would start with vacuum leaks and move to IAC then MAP and TPS. Does the engine start up right away after it dies? Does it take a little bit of cranking first? Does the engine stumble before dying? Or does it just die? The reason that I ask those questions is the 4.0 has had a long standing problem with the CPS. It's hard to catch if you have never had the problem before because it's sporadic and hard to trace. The only true way to check is to replace it and see if the problem goes away. Try a few things and post your results, there's a lot of good help on this board. Most of us have had the same problems you have had, or will have. I have a little over 270k mi. on my rig, so I have had most of the problems that can happen to an XJ.

Good luck,
Neil

 

[herreraxto]

The same thing happend to me its a 99 i took the TB unscrew just the IAC sensor and left the other two and start to clean them whit seafoam spray cleaner and now i am having the high idle

 

[daddyphatsacs]

Does the engine start up right away after it dies? Does it take a little bit of cranking first? Does the engine stumble before dying? Or does it just die? The reason that I ask those questions is the 4.0 has had a long standing problem with the CPS. It's hard to catch if you have never had the problem before because it's sporadic and hard to trace. The only true way to check is to replace it and see if the problem goes away. Try a few things and post your results, there's a lot of good help on this board. Most of us have had the same problems you have had, or will have. I have a little over 270k mi. on my rig, so I have had most of the problems that can happen to an XJ.

Good luck,
Neil

Yes, the engine starts right back up after dieing. It doesn't seem to stumble a whole lot, it just kind of quietly dies when idiling. When I first start it up it seems to run fine, but it seems like after it warms......the idle gets progressively lower. When I idle the RPMs fluctuate, between 300 and 1000 (I think that is what it is...off the top of my head). When I first started having problems, I swapped out the battery......before I did that, I had a very hard time getting it to restart. I switched out the CPS back in October, before I did that my Jeep wasn't running at all. After the CPS swap, it ran fine. Now this problem......do you think there is a chance that it has gone bad again?

Last night I fiddled around with the IAC, my check engine light hadn't been coming on. After I unplugged my IAC, and plugged it back in again.......when I started the Jeep my check engine light came on. My other issue is trying to get the two bolts off that are holding the IAC, I'm not much of a mechanic (thats an understatment)....so I'm wondering if I am doing something wrong. It seemed that I was fighting a little too much last night trying to remove it. Any tricks involved? I have a 2001 4.0 Cherokee Sport.

I'm about ready to run my head into a wall with this vehicle....

Thanks for all the help.

 

[Neil]

Yes, the engine starts right back up after dieing. It doesn't seem to stumble a whole lot, it just kind of quietly dies when idiling. When I first start it up it seems to run fine, but it seems like after it warms......the idle gets progressively lower. When I idle the RPMs fluctuate, between 300 and 1000 (I think that is what it is...off the top of my head). When I first started having problems, I swapped out the battery......before I did that, I had a very hard time getting it to restart. I switched out the CPS back in October, before I did that my Jeep wasn't running at all. After the CPS swap, it ran fine. Now this problem......do you think there is a chance that it has gone bad again?

Last night I fiddled around with the IAC, my check engine light hadn't been coming on. After I unplugged my IAC, and plugged it back in again.......when I started the Jeep my check engine light came on. My other issue is trying to get the two bolts off that are holding the IAC, I'm not much of a mechanic (thats an understatment)....so I'm wondering if I am doing something wrong. It seemed that I was fighting a little too much last night trying to remove it. Any tricks involved? I have a 2001 4.0 Cherokee Sport.

I'm about ready to run my head into a wall with this vehicle....

Thanks for all the help.

It doesn't sound like the CPS. It could be the IAC or the MAP. The IAC is held on by Torx bolts. If it has never been removed the bolts have Loctite on them. Heat will help remove them. You have to be careful using heat near the TB. Make sure that the vehicle has been off long enough for any fuel in the intake to evaporate. Use a small pencil torch or even a lighter to heat the bolts and then try to remove them. Make sure that you have right size Torx, they strip easily with the wrong size Torx. And don't try to use Allen wrenches. If you are using the screwdriver style you really have to tork on it (no pun intended) (ok maybe a little) They have Torx wrenches that fit on your ratchet that work much better than the screwdriver style. Someone mentioned Sea Foam earlier. That stuff works great.

Neil

 

[xjbubba]

All the AIC is, is a controlled vacuum leak. A vacuum leak anywhere in the system will cause the idle to increase. Generally, high idle is caused by a dirty port in the throttle body where the AIC piston seats. This dirt allows vacuum to leak arround the AIC's plunger. The plunger itself could be dirty as well. Since you've replaced the AIC, it's probably not the culprit. It still could be a dirty throttle body, a leaking throttle body gasket, or even leaks arround the butterfly shaft in the throttle body(not likely). Most likely is a cracked vacuum line connected to the intake manifold. Check all of those hoses with carb cleaner while the engine is running. Spray each one and observe whether the engine speed changes.

 

[red91]

I must have been the only guy to notice that this got resurected from 9-11-2004.


:yelclap:

 

[Neil]

I must have been the only guy to notice that this got resurected from 9-11-2004.


:yelclap:

That's how you can tell that people are actually searching!!! Not just blindly asking questions that have been asked and answered a million times already.

 

[Neil]

Last night I fiddled around with the IAC, my check engine light hadn't been coming on. After I unplugged my IAC, and plugged it back in again.......when I started the Jeep my check engine light came on.

Do you know how to check your engine codes? If not you need to get a Chilton's or a Haynes. They will explain how to check and read codes. The codes most often will they'll you what is wrong. Your on board computer is a great diagnostic tool.

Neil

 

[red91]

That's how you can tell that people are actually searching!!! Not just blindly asking questions that have been asked and answered a million times already.

True True...I'm just hoping that he didn't wait that long for an answer, or that someone didn't try to help him a year and a half later...

 

[Neil]

True True...I'm just hoping that he didn't wait that long for an answer, or that someone didn't try to help him a year and a half later...

That would be a very patient man!

 

[daddyphatsacs]

Thanks for the help so far fellas. I'm going to run the rig over to Autozone tonight to have them check run a test on my check engine light (I'm going cheap ) After that, I'm going to try to get the IAC off (hopefully tonight). I recently purchased some carb/choke cleaner, will that be sufficent for cleaning the IAC? Or should I return it and get the sea foam? Anyone know what size the torx is on that? Thanks again.

 

[Neil]

Thanks for the help so far fellas. I'm going to run the rig over to Autozone tonight to have them check run a test on my check engine light (I'm going cheap ) After that, I'm going to try to get the IAC off (hopefully tonight). I recently purchased some carb/choke cleaner, will that be sufficent for cleaning the IAC? Or should I return it and get the sea foam? Anyone know what size the torx is on that? Thanks again.

Fuel injection/throttle body cleaner is better for the plastics than carb cleaner, but it will work fine. The Sea Foam works great. It also allows you to soak the IAC without hurting it. You can also put the rest of the Sea Foam down the intake to clean the valves and combustion chambers.

Neil

 

[red91]

You can also put the rest of the Sea Foam down the intake to clean the valves and combustion chambers.

Neil

he he he.....read the instructions before you do it...and be in an open area away from your neighbors.

The show is more than they'll want to see. But yeah...it works really good.

 

[Neil]

he he he.....read the instructions before you do it...and be in an open area away from your neighbors.

The show is more than they'll want to see. But yeah...it works really good.

Just tell the neighbors that It's a mosqutoe abatement vehicle.:gee:

 

[daddyphatsacs]

Fuel injection/throttle body cleaner is better for the plastics than carb cleaner, but it will work fine. The Sea Foam works great. It also allows you to soak the IAC without hurting it. You can also put the rest of the Sea Foam down the intake to clean the valves and combustion chambers.

Neil

Thanks again for all the info fellas. I removed the IAC, and cleaned that along with the throttle body. I fired it up, and she ran normal. The idle didn't drop off, or stall out like it had been.....Actually it had been doing that earlier this evening when I was driving it around. I drove it around after fixing it, and when I came to a stop, still no problems. I let it run for a while, and normally when it had been acting up, I would have definately saw something by then. I'm thinking that did the trick! I used some throttle body cleaner and a toothbrush. I only sprayed it for a handful of seconds (following the directions on the bottle). I scrubbed the IAC also......both sections were pretty grimey. I didn't get fancy, just kind of plugged away at it.

Ironically, when I took the rig over to Auto Zone, the code was for a TPS. After I cleaned the IAC, I disconnected the battery for a few minutes (doesn't that reset it?), and when I turned it back on.......there was no check engine light anymore. Whatever I did seemed to work.

Thanks again, you guys were a great help.

 

[Neil]

Thanks again for all the info fellas. I removed the IAC, and cleaned that along with the throttle body. I fired it up, and she ran normal. The idle didn't drop off, or stall out like it had been.....Actually it had been doing that earlier this evening when I was driving it around. I drove it around after fixing it, and when I came to a stop, still no problems. I let it run for a while, and normally when it had been acting up, I would have definately saw something by then. I'm thinking that did the trick! I used some throttle body cleaner and a toothbrush. I only sprayed it for a handful of seconds (following the directions on the bottle). I scrubbed the IAC also......both sections were pretty grimey. I didn't get fancy, just kind of plugged away at it.

Ironically, when I took the rig over to Auto Zone, the code was for a TPS. After I cleaned the IAC, I disconnected the battery for a few minutes (doesn't that reset it?), and when I turned it back on.......there was no check engine light anymore. Whatever I did seemed to work.

Thanks again, you guys were a great help.

The IAC gets pretty ugly. A little Sea Foam every now and again in the TB Helps keep things cleaner. They still get dirty, just not as bad. Good to hear that you're up and running again. Keep an eye on that TPS. I bought a new TPS and two weeks later It was broken again. Brand new doesn't mean a whole lot. If a TPS code comes up again replace it. Try and find the lifetime warranty, that way you can change them out whenever you feel like it.

Neil

 

[dieselenthusiast]

Subscribing to learn…… Excellent thread……….. I just need to figure out what the initials IAC, TPS, MAP, and CPS actually stand for and locate each component/sensor on the vehicle. And I really need to buy a Haynes or FSM. I’m going to use the Amsoil Power Foam carburetor/injector cleaner tomorrow. I just bought a 2000 XJ with 186,000 miles. The vehicle idles high sometimes, so I figured it wouldn’t hurt to clean her out. Is there anything that I need to spray on the outside? According to Amsoil, I’m suppose to spray the entire can into the intake.

 

[kastein]

Subscribing to learn…… Excellent thread……….. I just need to figure out what the initials IAC, TPS, MAP, and CPS actually stand for and locate each component/sensor on the vehicle. And I really need to buy a Haynes or FSM. I’m going to use the Amsoil Power Foam carburetor/injector cleaner tomorrow. I just bought a 2000 XJ with 186,000 miles. The vehicle idles high sometimes, so I figured it wouldn’t hurt to clean her out. Is there anything that I need to spray on the outside? According to Amsoil, I’m suppose to spray the entire can into the intake.

Since you have an intermittent high idle, I'd pull the IAC off the throttle body (you will need a stubby torx 20 driver) and use an old toothbrush and some throttle body cleaner to clean both the IAC plunger (be gentle) and the hole that it goes into / the hole that the plunger seats against.

IAC = Idle Air Controller, a step motor solenoid plunger type valve that controls the amount of air let into the intake at idle
TPS = Throttle Position Sensor, lets the ECU/TCU know how much air you are putting into the intake
MAP = Manifold Air Pressure sensor
CPS = Crank Position Sensor, lets the ECU know what angle the crankshaft is at so it can time ignition and injection pulses properly
ECU = Engine Control Unit, also PCM (Powertrain Control Module) and a few other names
TCU = Transmission Control Unit
MAT = Manifold Air Temperature sensor
NSS = Neutral Safety Switch, tells the ECU what position the gearshift is in so it can lock out the starter solenoid for safety when not in P/N, etc
CCD Bus = Chrysler Collision Detection bus, a two wire serial data bus used by the ECU/TCU/other portions of the system to communicate

There are a whole bunch of others, but those are the most commonly referred to three letter acronyms in Jeep electrical work.

 

[dieselenthusiast]

Since you have an intermittent high idle, I'd pull the IAC off the throttle body (you will need a stubby torx 20 driver) and use an old toothbrush and some throttle body cleaner to clean both the IAC plunger (be gentle) and the hole that it goes into / the hole that the plunger seats against.

Thanks for all the information. I have a question, are you talking about removing the two torx in the photo below?