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Old 12-26-2013, 11:10 AM   #1
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Idle Problem on 1997 TJ Sports

Jeep info:
1997 Jeep Wrangler Sports 4.0L
215,xxx miles
5 Speeds
A/C
(I do have jeep build if needed)

Problem:
Well, I was out wheelin about a week ago and I had to go threw a pretty big puddle, It was deep enough to cover 3/4 of my rims (stock suspension), but not my engine, had to have a little speed so some water went on top of the hood, and a lil in the engine compartment. After I got out of the puddle I did open my hood and inspected to make sure everything was okay & secured. I also inspected the intake well to make sure a lot of water didn't get inside, I have a K&N Air intake installed.

Ever since I have done this my jeep has intermittently been idling weird. When I start up it'll idle normal, after engine is warm and stop at a light, it'll be idling around 1300-1500rpm, then if I step on the gas and spike it real close to 3000rpm, the idle will return to normal (a little below 1000rpm looks like 600-700rpm).

I have inspected vacuum hoses and check engine light is off.

Thank for your help Jeepers!

-Cray

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Old 12-26-2013, 11:53 AM   #2
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Idle

Yeah, was having idleing issues also. It wasn't all the time, like throttle was hanging up at around 1300 rpms. Went to Auto Zone and got some good throttle body spray cleaner, took off air cleaner tube and sprayed cleaner around butterfly in TB as per cleaner instructions. All is good now, idle comes right back down to normal. Keep us posted.

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Old 01-01-2014, 09:21 PM   #3
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POSSIBLE SOLUTION:
I had a similar problem with the idle until last week with my 97 4.0. I also had a cracked header. Over the weekend I took off the header & intake manifold to repair the header. I found that the INTAKE ports & HEAD ports were completely crudded up from all the crap gas we have to use over the years. I scraped the head ports till they were clean & the intake ports. .I then sprayed carb clean on some scotch brite to get the ports clean as new. Then rinced it all & the injectors with carb clean & used my air pistol to dry it out. I reassembled everything & fired it up. It smoked for 1 sec then cleared out. The jeep idles perfectly now & has a lot more power . I actually think its better on gas too. I found this problem by accident, I couldn`t reassemble the parts without cleaning them.
So, if you spray the carb/injector cleaner in its a minor fix. It took me about a hour to clean all that correctly & well worth it. My Jeep has 150k on it & it runs like my old jeep with 60k on it now! Crazy! just my 2c.
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Old 03-06-2014, 05:30 PM   #4
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Quote:
Originally Posted by Rocky Bar View Post
Yeah, was having idleing issues also. It wasn't all the time, like throttle was hanging up at around 1300 rpms. Went to Auto Zone and got some good throttle body spray cleaner, took off air cleaner tube and sprayed cleaner around butterfly in TB as per cleaner instructions. All is good now, idle comes right back down to normal. Keep us posted.

Well, took the throttle body off the intake manifold, clean the body and sensors and put back on...for a day or two it fired up pretty quick. Now it take a few 3-5 seconds to start....feel like forever holding the starter down trying to start...but after the engine if warm, it fires up, quick!

Any thoughts?

Thanks!
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Old 03-08-2014, 02:02 PM   #5
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*bump
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Old 03-08-2014, 02:22 PM   #6
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Mine starts off idling rough. On warm days I've got to let it sit for about 5 minutes before I start rolling. If not it jerks at anything faster then coasting until it gets warmed up.
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Old 03-08-2014, 02:47 PM   #7
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A slow start after it sits a while, especially overnight, is commonly caused by the check valve in the fuel pump assembly leaking & allowing all the fuel in the engine to drain out and back into the gas tank. The slow start is how long it takes for the fuel pump to get fuel back up to the engine. Replacing the fuel pump/fuel pressure regulator is the fix.

You can pretty well confirm this is the engine is quick to start when it has been running recently but very slow to start if it has been sitting an extended period of time... giving the check valve leak enough time to let the fuel drain down out of the engine.
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Old 03-08-2014, 02:53 PM   #8
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Originally Posted by Jerry Bransford View Post
A slow start after it sits a while, especially overnight, is commonly caused by the check valve in the fuel pump assembly leaking & allowing all the fuel in the engine to drain out and back into the gas tank. The slow start is how long it takes for the fuel pump to get fuel back up to the engine. Replacing the fuel pump/fuel pressure regulator is the fix.

You can pretty well confirm this is the engine is quick to start when it has been running recently but very slow to start if it has been sitting an extended period of time... giving the check valve leak enough time to let the fuel drain down out of the engine.
Very Helpful Jerry! Thanks!

You seem like you have a lot of knowledge (see's 25k+ post). I have another issue if you don't mind me help troubleshooting...When my engine (cold) you hear a very loud knocking/raddle'ing sound. After the engine is warm, knocking sound slightly fads. Think it's valves knocking?

Thanks!
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Old 03-08-2014, 03:01 PM   #9
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Thank you for the input Jerry. I will have to check that out and hopefully it will solve my issue.
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Old 03-09-2014, 11:43 AM   #10
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Quote:
Originally Posted by Cray View Post
Very Helpful Jerry! Thanks!

You seem like you have a lot of knowledge (see's 25k+ post). I have another issue if you don't mind me help troubleshooting...When my engine (cold) you hear a very loud knocking/raddle'ing sound. After the engine is warm, knocking sound slightly fads. Think it's valves knocking?

Thanks!
Without hearing it that's tough to know if it's a knock in the lower end caused by bad bearings or a clatter in the top end that is valve related. Sounds like you need to have that listened to by a knowledgeable mechanic to know for sure.
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Old 03-09-2014, 04:05 PM   #11
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Okay, I'll try and get you a video...
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Old 03-09-2014, 04:29 PM   #12
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The audio from a video is very likely going to be impossible to make a diagnosis from.

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