# fluctuating idle
**URL:** https://forums.speedlife.net/t/fluctuating-idle/124074
**Category:** SON240sx Automotive
**Created:** [May 1, 2009, 7:01pm UTC](https://forums.speedlife.net/t/fluctuating-idle/124074 "2009-05-01T19:01:44Z")
**Posts on this page:** 20
**Page:** 1
### Author:  [@89\_coupe](https://forums.speedlife.net/u/89_coupe)
#### Post date: [May 1, 2009, 7:01pm UTC](https://forums.speedlife.net/t/fluctuating-idle/124074/1 "2009-05-01T19:01:44Z")
ok. i already posted this but i have more details with my problem. i have a 1989 240sx with a ka24e. 118 000km on it. when i start it up everything is running perfectly fine. idle is a bit high, around 1600rpm. once the car is about at running temperature my idle starts to go crazy. revs up to about 2000rpm then drops back down to 1600rpm. creeps back up and drops. it does this about every 2 seconds. i checked my vacuum lines and replaced one that had a crack at the end. i pulled off my idle air control valve and it wasnt all that gunked up with carbon. bit i still cleaned it with some intake cleaner. still have the problem. seen if it was a coolant bubble like others said in the other post. nope not it. so any ideas. i asked my auto teacher and he said theres a possibility its an o2 sensor. so could it be an o2 sensor?
its like this when it warms up [http://www.youtube.com/watch?v=jCcN9zHmCCk&feature=related](http://www.youtube.com/watch?v=jCcN9zHmCCk&feature=related)
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### Author:  [@Stiky](https://forums.speedlife.net/u/Stiky)
#### Post date: [May 1, 2009, 7:03pm UTC](https://forums.speedlife.net/t/fluctuating-idle/124074/2 "2009-05-01T19:03:30Z")
check TPS, MAF, 02, all of those misc connectors, emissions shit as well.
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### Author:  [@87s15lt1](https://forums.speedlife.net/u/87s15lt1)
#### Post date: [May 1, 2009, 7:25pm UTC](https://forums.speedlife.net/t/fluctuating-idle/124074/3 "2009-05-01T19:25:45Z")
tps, timing and base idle.
all 3 work in conjunction.
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### Author:  [@spynn56](https://forums.speedlife.net/u/spynn56)
#### Post date: [May 1, 2009, 7:29pm UTC](https://forums.speedlife.net/t/fluctuating-idle/124074/4 "2009-05-01T19:29:26Z")
plus ok? wires burnt?
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### Author:  [@Stiky](https://forums.speedlife.net/u/Stiky)
#### Post date: [May 1, 2009, 8:06pm UTC](https://forums.speedlife.net/t/fluctuating-idle/124074/5 "2009-05-01T20:06:16Z")
Yeah most likely tps is fucked
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### Author:  [@89\_coupe](https://forums.speedlife.net/u/89_coupe)
#### Post date: [May 2, 2009, 4:57am UTC](https://forums.speedlife.net/t/fluctuating-idle/124074/6 "2009-05-02T04:57:33Z")
if it was the tps wouldnt my idle be all over the place from start up or no? cuz it only starts happening when my car is almost running temp.
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### Author:  [@89\_coupe](https://forums.speedlife.net/u/89_coupe)
#### Post date: [May 2, 2009, 5:12am UTC](https://forums.speedlife.net/t/fluctuating-idle/124074/7 "2009-05-02T05:12:36Z")
and i dont think it is a tps because it is only there to tell you how much your foot is on the gas. it does change the idle.
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### Author:  [@sidewayz240](https://forums.speedlife.net/u/sidewayz240)
#### Post date: [May 2, 2009, 9:39am UTC](https://forums.speedlife.net/t/fluctuating-idle/124074/8 "2009-05-02T09:39:17Z")
Does it rev up and drive normally other then this?
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### Author:  [@89\_coupe](https://forums.speedlife.net/u/89_coupe)
#### Post date: [May 2, 2009, 12:43pm UTC](https://forums.speedlife.net/t/fluctuating-idle/124074/9 "2009-05-02T12:43:41Z")
i havnt done any real driving because its not insured. but i have taken it around my shop that i work at a couple of times and it doesnt seem to be doing it when driving. and when it is just sitting there if i give it some gas it will drop down and it wont start fluctuating for a couple seconds.
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### Author:  [@89\_coupe](https://forums.speedlife.net/u/89_coupe)
#### Post date: [May 2, 2009, 1:13pm UTC](https://forums.speedlife.net/t/fluctuating-idle/124074/10 "2009-05-02T13:13:07Z")
this is pretty much what is happening to my 240. and it only happens around running temp. [http://www.youtube.com/watch?v=jCcN9zHmCCk&feature=related](http://www.youtube.com/watch?v=jCcN9zHmCCk&feature=related)
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### Author:  [@Tacoboy](https://forums.speedlife.net/u/Tacoboy)
#### Post date: [May 2, 2009, 2:45pm UTC](https://forums.speedlife.net/t/fluctuating-idle/124074/11 "2009-05-02T14:45:41Z")
Don’t listen to the above until you bleed your coolant system. It sounds like you have a bubble. To burp it, jack it up to approx 30 degrees in the air from the front, pop off the rad cap, and leave it running till you see all of the air bubbles escape. If you need more indepth info, please feel free to PM.
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### Author:  [@Coop\_LE](https://forums.speedlife.net/u/Coop_LE)
#### Post date: [May 2, 2009, 2:52pm UTC](https://forums.speedlife.net/t/fluctuating-idle/124074/12 "2009-05-02T14:52:25Z")
air in your cooling system has nothing to do with engine rpm, or idle problems
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### Author:  [@89\_coupe](https://forums.speedlife.net/u/89_coupe)
#### Post date: [May 2, 2009, 4:45pm UTC](https://forums.speedlife.net/t/fluctuating-idle/124074/13 "2009-05-02T16:45:10Z")
yea thats what i thought cuz coolant doesnt run to the iacv
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### Author:  [@Tacoboy](https://forums.speedlife.net/u/Tacoboy)
#### Post date: [May 3, 2009, 11:06am UTC](https://forums.speedlife.net/t/fluctuating-idle/124074/14 "2009-05-03T11:06:20Z")
Coop LE, you are wrong. A fluctuating idle CAN be caused by a coolant bubble - the IACV wont recieve the proper amount of coolant. There are two small coolant lines runnign right do it, underneath the intake manifolt - they T off of the large coolant line going alongside the block. Try it man, what do you have to lose? Use a process of elimination instead of going and blowing a tonne of cash on all the sensors that are likely fine.
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### Author:  [@89\_coupe](https://forums.speedlife.net/u/89_coupe)
#### Post date: [May 3, 2009, 6:31pm UTC](https://forums.speedlife.net/t/fluctuating-idle/124074/15 "2009-05-03T18:31:15Z")
well wen i pulled off my iacv there was no coolant. my shop even said that it doesnt run off coolant. now today i unplugged my tps and bam idles at 750rmp and not fluctuating. i plug it back in and its still at 750rpm and not fluctuating so i think i found it. and that was at 3 befor i went to work. now after work i checked it again but this time its a high idle but not fluctuating. so is it a tps?
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### Author:  [@87s15lt1](https://forums.speedlife.net/u/87s15lt1)
#### Post date: [May 3, 2009, 8:55pm UTC](https://forums.speedlife.net/t/fluctuating-idle/124074/16 "2009-05-03T20:55:56Z")
What did I say about the tps? I forget now
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### Author:  [@89\_coupe](https://forums.speedlife.net/u/89_coupe)
#### Post date: [May 4, 2009, 5:53pm UTC](https://forums.speedlife.net/t/fluctuating-idle/124074/17 "2009-05-04T17:53:10Z")
lol i think it was something like check it out aha 😛
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### Author:  [@87s15lt1](https://forums.speedlife.net/u/87s15lt1)
#### Post date: [May 4, 2009, 6:03pm UTC](https://forums.speedlife.net/t/fluctuating-idle/124074/18 "2009-05-04T18:03:39Z")
never hurts to try
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### Author:  [@89\_coupe](https://forums.speedlife.net/u/89_coupe)
#### Post date: [May 4, 2009, 6:10pm UTC](https://forums.speedlife.net/t/fluctuating-idle/124074/19 "2009-05-04T18:10:13Z")
yea. lol i have a buddy thats coming over sat. and were just gunna swap parts till mine works and his dont aha
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### Author:  [@240xcsv](https://forums.speedlife.net/u/240xcsv)
#### Post date: [May 5, 2009, 5:46pm UTC](https://forums.speedlife.net/t/fluctuating-idle/124074/20 "2009-05-05T17:46:48Z")
holy misinformation crap in this thread… damn… bubbles in the radiator?! WTH?!
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