Low RPM - JeepForum.com
 
LinkBack Thread Tools
post #1 of 9 Old 06-30-2008, 06:47 AM Thread Starter
tecumsa
Senior Member
 
tecumsa's Avatar
1997 TJ Wrangler 
 
Join Date: Nov 2005
Location: Plum, Pa. 15239
Posts: 822
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?

tecumsa is offline  
Sponsored Links
Advertisement
 
post #2 of 9 Old 06-30-2008, 10:00 AM
RnEmOvr
Have Cummins, Will tow.
 
RnEmOvr's Avatar
1999 TJ Wrangler 
 
Join Date: Mar 2005
Location: El Paso
Posts: 11,914
check your ignition system, its getting wet cause bad spark, i used to have that problem alot
RnEmOvr is offline  
post #3 of 9 Old 06-30-2008, 10:13 AM Thread Starter
tecumsa
Senior Member
 
tecumsa's Avatar
1997 TJ Wrangler 
 
Join Date: Nov 2005
Location: Plum, Pa. 15239
Posts: 822
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.
tecumsa is offline  
post #4 of 9 Old 06-30-2008, 12:19 PM
retroflow
Registered User
1997 TJ Wrangler 
 
Join Date: Dec 2005
Location: Meriden, CT
Posts: 307
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.

'97 Jeep TJ (SE) - Sold. Goodbye ol' Paint. Be good.
retroflow is offline  
post #5 of 9 Old 06-30-2008, 03:02 PM Thread Starter
tecumsa
Senior Member
 
tecumsa's Avatar
1997 TJ Wrangler 
 
Join Date: Nov 2005
Location: Plum, Pa. 15239
Posts: 822
Forgive me for being stupid, AIS motor? TPS is, I assume, the throttle position sensor.
tecumsa is offline  
post #6 of 9 Old 07-01-2008, 06:11 AM
Pillswoj
Registered User
1999 TJ Wrangler 
 
Join Date: Dec 2007
Location: Ontario, Canada
Posts: 2,765
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

Friends don't let Friends run Bosch
Pillswoj is offline  
post #7 of 9 Old 07-03-2008, 12:32 PM
retroflow
Registered User
1997 TJ Wrangler 
 
Join Date: Dec 2005
Location: Meriden, CT
Posts: 307
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.

'97 Jeep TJ (SE) - Sold. Goodbye ol' Paint. Be good.
retroflow is offline  
post #8 of 9 Old 07-04-2008, 12:08 PM Thread Starter
tecumsa
Senior Member
 
tecumsa's Avatar
1997 TJ Wrangler 
 
Join Date: Nov 2005
Location: Plum, Pa. 15239
Posts: 822
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.
tecumsa is offline  
post #9 of 9 Old 07-04-2008, 01:23 PM
Pillswoj
Registered User
1999 TJ Wrangler 
 
Join Date: Dec 2007
Location: Ontario, Canada
Posts: 2,765
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.

Friends don't let Friends run Bosch
Pillswoj is offline  
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the JeepForum.com forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid e-mail address for yourself.



Email Address:
OR

Log-in









Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.




Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome