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Old 11-15-2015, 10:35 AM
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Annoying idle issue

Long story short I had a strange idle in the past where the rpms would drop maybe 100-200 and the jeep would rumble for a second. It always returned to normal and only did this once per stop.

Taking advice from you fellows here and there, I cleaned the entire TB and everything attached. The IAC was black and filthy. I noticed fuel in the intake manifold. Not a puddle or anything like that but a fine layer of it. I tested my fuel pressure and it was normal. It did not drop a bit. I decided to swap out my injectors for a set I found on ebay:

Jeep Wrangler TJ 97 02 2 5L 4 Cylinder 4 Hole Upgrade Fuel Injectors w Video | eBay

Everything went together fine and it was working as it should with a smoother idle and all that. Then it started up again and even worse this time. It drives fine but when I come to a stop the rpms will jump about 100 and then instantly drop 200 and the jeep would rumble. It does this every 10-15 seconds at idle and only after driving it a while. I also noticed that it starts up at 1000 rpms when I first start it in the morning. It stays at 1000 until I drive it around a bit.

I'm not sure if this is from the different injectors or something else. Any one got any ideas?

1999 TJ 2.5L
Complete tune-up a couple months ago that included new 02 sensors.

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Old 11-15-2015, 11:21 AM   #2
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I had a similar issue with my 98 wrangler 4.0. Eventually it wouldn't start unless I opened the throttle a bid. I cleaned the TB and IAC. NO help. Replaced the IAC. No help. Finally I disconnected and cleaned my battery terminals and cleaned all of the grounds. Main grounds are on the firewall and on pass. side of engine block. It's been a few days now and it starts fine and no idle bubble on stops. Easy and inexpensive place to start. Good luck, BB

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Old 11-15-2015, 10:59 PM
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Well my battery terminals are brand new and so is the battery so I'll look at the grounds tomorrow. Thanks.
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Old 11-16-2015, 03:46 PM   #4
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I have the same issue would love to find some solid advice on this. The only thing is mine is doing the same at startup as well. I have to hold it in rev for a minute or two for it to stay running on its own. After that I get the low RPMS. I have replaced the TPS,IAC and MAP all with MOPAR parts still having the issue. I can't figure it out.
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Old 11-16-2015, 03:53 PM   #5
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Quote:
Originally Posted by m2b1969 View Post
I have the same issue would love to find some solid advice on this. The only thing is mine is doing the same at startup as well. I have to hold it in rev for a minute or two for it to stay running on its own. After that I get the low RPMS. I have replaced the TPS,IAC and MAP all with MOPAR parts still having the issue. I can't figure it out.
i'm going out on a limb here but CPS? When I had to change mine it would cut off and would not start for a while and then after it started it wouldn't idle smoothly.
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Old 11-16-2015, 04:12 PM   #6
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Is there a way to test the CPS first?
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Old 11-16-2015, 04:30 PM   #7
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Is there a way to test the CPS first?
not that i know of.
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Old 11-16-2015, 07:31 PM   #8
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My 97 TJ does the same thing. Well I should say did. It was doing the same thing on idle and every now and then the startup thing. Also it would kick while accelerating. I just drove it for a few days and it went away. Never replaced anything. Wish all of my problems on my jeep went away like that.
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Old 11-17-2015, 07:48 AM   #9
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iddle issues

Newbie
I am having same issues but
sorry guys but what is?
TPS,IAC, MAP and lastly CPS.
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Old 11-18-2015, 12:47 PM   #10
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Welcome aboard. I'm new here too. However,
TPS= Throttle position sensor
IAC = Idle Air Control
MAP = Manifold Absolute pressure sensor
CPS = Cam or Crankshaft position sensor

Hope this helps
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Old 11-18-2015, 06:00 PM   #11
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Sure does, thanks man!

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