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Old 11-16-2011, 09:32 PM   #1
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1998 Wrangler Sahara with Fuel Issues? Please Help!!!

Year: 1998
Type: Wrangler Sahara

Vehicle History:
My father-in-law bought the Jeep around 2006 in North Carolina. Shortly after he moved out to Arizona and lived there until he passed away this past Spring. I flew out to Arizona this past June to pick up the Jeep and drove it back across the country. During the trip back we had mechanical problems 80 miles east of El Paso. A Pep Boys store determined that the problem was a bad fuel pump (in tank), which was replaced and we then drove on with no problems…other than a few noises (I replaced the exhaust pipe gasket which fixed most of the noise) and the occasional smell of gas. There are many other issues, but those were the main ones. After getting back to North Carolina we found the cause of the gas smell. The valve core on the Schroder valve was broken (spring wasn’t working) and gas was leaking out. I replaced the valve core, which stopped the gas leaking and thus the smell.

Problem:
Since shortly after (can’t remember if it was immediately, but within a few days) whenever the vehicle is started cold (mostly…will explain), it cannot be driven immediately. Within a minute or so the engine gets sluggish and hesitates like it’s not getting gas. It lasts for approximately 30 seconds (during which time you hope you don’t get run over by another vehicle) and then drives fine. So, initially my work around I discovered was to simply let the Jeep run for around 5 minutes before putting in drive. I noticed that when the temperature gauge got about halfway up, then it was OK to go. During the idle time while the temp is going up, there is a period of rough idle then it calms down and it’s usually good to go. I have discovered however that this is not a complete fix. For instance, if the Jeep is driven and then sits for around 30 minutes or so (still shows as warm on the temp gauge), it will still do it. So, I’m ruling out the temp is the overall issue.

So, I’m trying to come up with solutions. Please share thoughts.

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Old 11-16-2011, 11:13 PM   #2
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Almost sounds like the IAC (Idle Air Control) is hanging up on you.
It's bolted to the side of the throttle body, 2 bolts.

Simple pintle valve that moves back and forth to control the idle speed. They can get a build up of deposits on them and hang up, causing the jeep to idle rough, stall, idle too slow.

When it's cold the valve could be stuck, and it takes the time for the engine to warm up for it to free up. Once it sits for a bit, not moving, it hangs up again until it works free again.

Easy to clean it. Pull the two bolts, unplug the IAC, and pull it out of the throttle body. Clean the valve and it's bore inside the throttle body with carb cleaner.

Reassemble and see what happens.

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Old 11-17-2011, 03:04 PM   #3
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Shelby...Thanks for the input. I'll give that a whirl and see if it helps out. I'm a newbie so the directions are also helpful!
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Old 11-28-2011, 05:57 PM   #4
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Shelby: I finally got around to trying this. I ended up just removing the whole throttle body for a good clean up. While it was in need of a cleaning and I'm happy to have gone through the process, it did not solve the problem.

Any other thoughts?
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Old 11-28-2011, 06:04 PM   #5
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Is it giving you any codes? The only thing of the top of my head would be the throttle position sensor.
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Old 11-28-2011, 06:14 PM   #6
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Thanks for the reply 4Jeepn. No codes have come up enough to make the "check engine" light appear. I had a local auto parts store run it a while back and they didn't get anything. I guess I can take it to the dealership and let them run it, but they want $90 and I'm screwed if it produces nothing. I tried the throttle position sensor with no luck...somehow I convinced the parts store to let me return it.
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Old 03-18-2013, 09:44 PM   #7
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I have been having the exact same problem with my 99 Sahara. When cold and even when warm, but after it sits for a few minutes...... It often hesitates on acceleration. After a couple minutes of driving it works itself out. Been going on for over a year. 2 dealerships are stumped plus another specialty shop. I cleaned IAC valve, replaced TPS, cleaned throttle body...... All for nothing. The dealer plugged his computer in to it while I drove once and told me that a couple cylinders were missing. Duh. I know that cuz it's hesitating! And he proceeded to tell me just to drive it till something breaks. Nice job guy. I'm going nuts trying to figure it out. My best guess is the computer may be throwing the wrong voltage to the 2 cylinders that are missing..... Bad computer? Rare I know but it happens. Any ideas anybody?
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Old 03-18-2013, 11:16 PM   #8
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Damn this sounds weird
I know the damn crank sensor screws up in jeeps but i though its the problem here
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Old 03-19-2013, 01:02 PM   #9
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I am having the same issue!!! I have a 98 Sport 4.0, there doesnt seem to be a rhyme or reason to it, whether the engine is warm or cold, but for the first 5 minutes of driving or so, it will all of a sudden just seem like the fuel is not getting to the engine or something. And its not even all the time, just every few times i drive! It is annoying the heck out of me. Took it to my mechanic who is a big off roader with a few jeeps, and he couldnt figure it out, even said that he thinks his old jeep did the same thing and he just ignored it... WRONG ANSWER!!! I havent owned the jeep long, so dont know if it did this to the PO, but i am lost on what to do... Surely someone has had this and found a fix, right?!?!
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Old 03-19-2013, 04:18 PM   #10
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In for more results and a answer
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Old 04-04-2013, 01:21 PM   #11
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any luck on the issue?
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Old 04-04-2013, 07:24 PM   #12
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replace the upstream o2 sensor
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Old 04-04-2013, 08:35 PM   #13
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This is what my 1st post(3-29-13)was about when I joined forum. bought my 98 Sahara off a buddy that has same problem. Local mechanic told him fuel injectors. Haven' t got a chance to change ones I just got off a blown motor buddy just changed. Quick check would be to switch them between cylinders before you by them. Hopin to do this next couple, got time to get out this weekend 4wheelin
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Old 04-05-2013, 12:57 AM   #14
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Try this, the valve core you put in, use a small screwdriver or something and press it down to see if there is an air pocket in the line. Wear safety glasses cause the line has pressure in it. Once gas shoots out release it and then try starting the jeep and see what happens.
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Old 05-06-2013, 08:58 AM   #15
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Mine appears to be fixed. Replaced both O2 sensors (if one is bad, probably a good idea to go ahead and knock em both out while your doing it) about 3 weeks ago, and havent had it happen since. also have seen a .75 mpg increase since doing it.

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