LJR nearly stalling on decel - JeepForum.com
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post #1 of 8 Old 09-25-2021, 11:24 AM Thread Starter
Hipmusicman
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LJR nearly stalling on decel

Have an '05 LJR that seems to want to stall on decel. Clutch or no clutch, doesn't matter as long as the engine is not in any way connected to the axles. Typically happens when coming down from anything 30mph+.
When the idle comes down super low, something near 200 or lower, the jeep revs itself to keep it running. When I'm at a stop, the rpm settles at around 600-700 like normal.

It might be worth mentioning that the tac isn't super accurate. When I start it up in the morning, immediately it revs up to 1200 or so then settles to around 700 during idle. However, the tac usually sticks at around 1100 and if I just barely tap the pedal it pops down to show around 800 and follows the engine speed. But it's still kinda sticky. When at a stop, the tac reads close to 300 but I know it's much higher than that. Just thinking it's sticky but if it's a symptom of the near stalling issue, I figured I'd mention it.

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post #2 of 8 Old 09-25-2021, 11:29 AM
CJ7-Tim
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Clean the Throttle body and the Idle Air Controller.


Cleaning the Idle Air Controller (IAC) :

Purchase sensor safe Throttle Body cleaner spray.

1. Remove the Throttle body from the intake manifold.
2. Remove the IAC with a good quality brand name TORX 15 driver (2 bolts)
3. Gently wiggle out the IAC from the throttle body
4. Clean the IAC with Throttle Body Cleaner (not carburetor cleaner). Use cleaner, a rag, and a toothbrush. Be gentle; don’t twist or pull on the IAC pintle as it is fragile and can be damaged easily
5. Also clean the IAC housing in the throttle body
6. While you have the Throttle Body off, give it a good cleaning also.
7. Reinstall IAC, the Throttle body, and check idle quality.
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post #3 of 8 Old 09-25-2021, 02:18 PM Thread Starter
Hipmusicman
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Quote:
Originally Posted by CJ7-Tim View Post
Clean the Throttle body and the Idle Air Controller.


Cleaning the Idle Air Controller (IAC) :

Purchase sensor safe Throttle Body cleaner spray.

1. Remove the Throttle body from the intake manifold.
2. Remove the IAC with a good quality brand name TORX 15 driver (2 bolts)
3. Gently wiggle out the IAC from the throttle body
4. Clean the IAC with Throttle Body Cleaner (not carburetor cleaner). Use cleaner, a rag, and a toothbrush. Be gentle; don’t twist or pull on the IAC pintle as it is fragile and can be damaged easily
5. Also clean the IAC housing in the throttle body
6. While you have the Throttle Body off, give it a good cleaning also.
7. Reinstall IAC, the Throttle body, and check idle quality.
Cleaned the IAC already but didn't get around to removing the TB. I'll try that soon.
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post #4 of 8 Old 09-25-2021, 08:21 PM
CJ7-Tim
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Quote:
Originally Posted by Hipmusicman View Post
Cleaned the IAC already ...
If it doesn't get better, suspect the IAC is faulty.

“We the people are the rightful masters of both Congress and the Courts,
not to overthrow the Constitution but to overthrow the men who would pervert the Constitution” Abraham Lincoln, 1859.
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post #5 of 8 Old 09-25-2021, 10:07 PM Thread Starter
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Quote:
Originally Posted by CJ7-Tim View Post
Quote:
Originally Posted by Hipmusicman View Post
Cleaned the IAC already ...
If it doesn't get better, suspect the IAC is faulty.
I did see a post about a low battery causing complete stalling. It cranks just fine in the morning but could be better. Maybe have the battery tested? To reinforce this, the lighting in the gauges fade a little when the rpm gets really low. Voltage reads about 14.
Low fuel pressure?
Bad MAP?
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post #6 of 8 Old 09-26-2021, 09:27 AM
CJ7-Tim
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A battery Load Test is a good idea and simple to do. Find a shop or parts store that has a battery Load Test machine. Handheld in-car battery testers are inaccurate, you want a test machine they put the battery into.

If you buy an IAC get a genuine Jeep part. Most auto parts stores sell cheap crappy Chinese made parts, some that even come with a "Lifetime Warranty". These parts are poorly manufactured and/or made from inferior materials. They are often out of specification, or even failed, right out of the box. The ones that are not faulty many times will have a short service life before they fail. Always buy top quality replacement parts and genuine Jeep engine sensors. Numerous threads detail long and frustrating searches for a "problem" that ended up being cured simply with genuine Jeep repair parts.

Cheap parts are cheap for a reason.

“We the people are the rightful masters of both Congress and the Courts,
not to overthrow the Constitution but to overthrow the men who would pervert the Constitution” Abraham Lincoln, 1859.
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post #7 of 8 Old 09-27-2021, 09:40 AM Thread Starter
Hipmusicman
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Quote:
Originally Posted by CJ7-Tim View Post
A battery Load Test is a good idea and simple to do. Find a shop or parts store that has a battery Load Test machine. Handheld in-car battery testers are inaccurate, you want a test machine they put the battery into.

If you buy an IAC get a genuine Jeep part. Most auto parts stores sell cheap crappy Chinese made parts, some that even come with a "Lifetime Warranty". These parts are poorly manufactured and/or made from inferior materials. They are often out of specification, or even failed, right out of the box. The ones that are not faulty many times will have a short service life before they fail. Always buy top quality replacement parts and genuine Jeep engine sensors. Numerous threads detail long and frustrating searches for a "problem" that ended up being cured simply with genuine Jeep repair parts.

Cheap parts are cheap for a reason.
Usually the best practice. There have been a few simple mechanical things I just buy cheap but typically sensors I buy genuine if I can.
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post #8 of 8 Old 10-08-2021, 09:30 PM Thread Starter
Hipmusicman
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Ran through a pretty basic remedy and all seems good.

Techron in the fuel, TB cleaner to the TB and IAC, let the engine suck on some B-12, and measured and tested the IAC.
There seems to be a decent amount of oil getting sucked into the intake which that combined with some of the carbon I encountered seemed to be causing some problems. I don't know fore sure what's causing the oil issue but it's for sure coming from the rear valve cover breather.

Thoughts on the oil issue?
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