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Unread 06-30-2008, 07:47 AM   #1
tecumsa
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Low RPM

This morning I had a hard time starting my Jeep, always happens after a lot of rain and the humidity is high (common occurrence in Pa). Drove down to the first stop sign and noticed that my idle RPM was on the low-side (1st mark on the gauge, 250 rpm?), stayed that way every time I came to a stop or shifted into neutral to drift down the hills. Big concern is that the battery meter dropped to near or under 12v during these times. Any ideas?

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Unread 06-30-2008, 11:00 AM   #2
RnEmOvr
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check your ignition system, its getting wet cause bad spark, i used to have that problem alot
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Unread 06-30-2008, 11:13 AM   #3
tecumsa
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Quote:
Originally Posted by rnemovr View Post
check your ignition system, its getting wet cause bad spark, i used to have that problem alot
I had thought of that, but the engine, even at 250, is running smooth, no feel of a miss.
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Unread 06-30-2008, 01:19 PM   #4
retroflow
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Have you tried cleaning the AIS motor inside your throttle body? Just a stab in the dark. You may want to try giving the AIS a good cleaning. The AIS controls the valve which regulates the throttle's idle air flow. In effect, it's an automatic choke. If it gets covered in gunk, oily tar and dirt, it may get sticky or jam up. I've seen one so fouled with tar that I'd be surprised if it could still operate properly. It's a movng part, so the less dirt on it the better.

Other than this, it could be something up with the TPS (for similar reasons that the AIS could malfunction) or your O2 Senors. I just had to change out the O2 sensors on my '97 as we approached the 100k mark - the upstream croaked at about 98k which is still normal. Fortunately, O2 sensors for the TJ are not too expensive anymore if you shop around. Mine were about $22 each. I knew to change them based on observable symptoms of my own. Very rough idle and black soot developing inside the tailpipe and on the spark plugs. Note: The O2 sensors were very sooty too.

Like I said, just a shot in the dark.
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Unread 06-30-2008, 04:02 PM   #5
tecumsa
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Forgive me for being stupid, AIS motor? TPS is, I assume, the throttle position sensor.
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Unread 07-01-2008, 07:11 AM   #6
Pillswoj
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Idle Air Controller / Solinoid IAC or IAS it is right beside the TPS on the throttle body. If you do a search there are many posts describing the removal and cleaning
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Unread 07-03-2008, 01:32 PM   #7
retroflow
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Quote:
Originally Posted by Pillswoj View Post
Idle Air Controller / Solinoid IAC or IAS it is right beside the TPS on the throttle body. If you do a search there are many posts describing the removal and cleaning
Right you are, sir.. Thanks.
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Unread 07-04-2008, 01:08 PM   #8
tecumsa
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THANK YOU! I replaced the IAC, as easy as everyone said it would be!

I haven't done much car work since high-school (68-72), carb days. Between college, work, and kids there hasn't been much time to spare, short of brake jobs and oil changes. It's been nice the last year getting back into it (kids are in college now ).

I followed Jerry's advice (http://www.jeepforum.com/forum/showt...light=Idle+Air) on replacing it. Two difference though, my screws were T-20, not T-25, not a major problem since I had both. I lacked the baby bottle brush, but found an alternative, 1" foam paint brush. Sprayed the inside with throttle cleaner, then spun the foam brush inside, left it clean as new.

Is there any difference between throttle cleaner and carb cleaner? I saw two different products, didn't seem like there was much of a difference in the chemicals.
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Unread 07-04-2008, 02:23 PM   #9
Pillswoj
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Don't think there is much difference between the cleaners, you want to make sure you get one that is labeled as "Sensor Safe" or something like that.
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