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low idle,sometimes


 
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uuberbob
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Age: 58
Joined: 05 Feb 2017
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Post: #1   PostPosted: Sun Feb 05, 2017 2:11 pm    Post subject: low idle,sometimes Reply with quote

I am new here, so if I dont follow proper etiquette, let me know. I have an 04 neon SXT that runs fine, starts fine, however when it comes to a stop light/sign it will idle down to about 600RPM. Not immedietly but will take 10-20 seconds and will slowly come down. If I put it in neutral and back to drive it will come back to about750/800 or so. during the winter it did not do this, it was always at the 750/800 area. today was above freezing and I drove it and it did the low idle thing. any ideas will help and thanks in advance. if your ideas are of the " maybe change your tires " or " it could be the color of your car " variety, dont waste your time or mine, please.
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occasional demons
Mr One World
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Age: 51
Joined: 03 May 2007
Posts: 19781
Location: Ashland, Ohio

2001 Dodge Neon ES

Post: #2   PostPosted: Mon Feb 06, 2017 4:33 am    Post subject: Reply with quote

About all you can do is use a soap based cleaner, and try cleaning the throttle body.

You can pull the cast aluminum IAC valve off the TB and clean that with carb cleaner, if it is carbon'ed up.

But the low idle thing is a common issue with neons. Most will idle down on a consistent basis.

You can also use a vacuum nipple and attach a hose to it, with a plug that has a drilled hole, and slowly increase the hole size to get a higher idle. you would want to plumb the hose to filtered air.


If the o2 sensor has never been changed, you might consider that, so it responds faster. It may not help the low idle issue, but in the off chance it is reponding sluggishly, it could be contributing to it.
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2001 neon ES MTX with '02 R/T PCM
1999 neon 2.4 EDZ MTX
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Dillmiester
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Age: 28
Joined: 31 Oct 2013
Posts: 21


2000 Plymouth Neon LX

Post: #3   PostPosted: Tue Feb 07, 2017 12:25 pm    Post subject: Reply with quote

You'll find the consensus of the community is that its common to neon's. Speculation is that the cause is an aggressive idle fuel conservation, and this is exacerbated with age and other factors that cause it to get in that 6** rpm range.

May be due to dirty and leaking valves, the valve guide seals going bad is common I'm pretty sure mine need to be replaced, I loose about a quart of oil every month or 2 depending on how I drive it. 

I've replaced so many things on my car and have improved it,  it comes and goes,  temperature change/humidity definitely plays a role.

I know I have a leak in my exhaust manifold and get a p0134. I'll be replacing that when I get my taxes back.

 Things I've replaced.

O2 Sensors with Denso's

Spark Plugs  NGK's, Denso's,  tried AC Delco's recently I'm pretty happy with em.

Spark Plug Wires
Coil Pack
Replaced and Sealed Spark Plug Tubes
Paper air filter Instead of K&N that came with the car.
IAC
PCV Valve 
Changed Engine Harness for various reasons.
Cleaned PCM connectors.
Fuel Pump
Camshaft and Crankshaft position Sensor
Throttle Postion Sensor and rewired with new connector some wires were fused together.
Survived a timing belt failure, had its timing belt changed, still pulls strong.

One thing that helps is putting it in park when sitting for long times in traffic.

If you had a 3 speed transmission I'd tell you to check for binding at the throttle plate.

I know some people don't like the idea, but you might want to consider a good Seafoam and distilled water cleaning. Just be careful with your amounts and use a fine spray, also water can collect in the bottom of the intake manifold so be mindful of that you might find some oil in there before you begin your cleaning.


A computer tune could fix this but I have a 2000 so no syked handheld for this car, I'll eventually get a 04 or higher.


Check this thread out also.

http://forum.2gn.org/viewtopic.php?t=51611&postdays=0&postorder=asc&start=120
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occasional demons
Mr One World
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Age: 51
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Location: Ashland, Ohio

2001 Dodge Neon ES

Post: #4   PostPosted: Wed Feb 08, 2017 5:23 am    Post subject: Reply with quote

Quote:
Posted: Sun Feb 05, 2017 2:11 pm


Quote:
Last Visited: Sun Feb 05, 2017 2:11 pm


Must not be too urgent....

My '01 idles at or below 600 rpm, because 210,000 miles, and low compression due to worn out rings.

It won't even run the A/C compressor, unless it is actually being driven. The PCM cuts it to keep it from stalling, rather than open the IAC valve a little more. Tard Bang
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2001 neon ES MTX with '02 R/T PCM
1999 neon 2.4 EDZ MTX
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uuberbob
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Post: #5   PostPosted: Wed Feb 08, 2017 9:28 am    Post subject: Reply with quote

I appreciate your responding " Dillmeister . So there is no ,as far as you know, one definitive reason for this situation. Its all, could be this,could be that. Two things I dont understand 1) the temperature relationship- this condition did not exist when the temperature was below freezing, and 2) why, when the idle drops, and when either I put the vehicle in neutral, or , toe tap the throttle does it come back to the " normal " idle speed. Any thoughts or ideas on those two?
Thanks
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occasional demons
Mr One World
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Age: 51
Joined: 03 May 2007
Posts: 19781
Location: Ashland, Ohio

2001 Dodge Neon ES

Post: #6   PostPosted: Wed Feb 08, 2017 10:53 am    Post subject: Reply with quote

The reaction to the temp difference could be the PCM changing things due to input from the ambient temp sensor input, engine coolant sensor input, as the thermostat isn't going to keep it at a 100% level temp.

In neutral or park, there isn't a load, so that alone will affect idle.

When you tap the gas, it makes the IAC valve move closer to closed, so it has to reset once the throttle plate shuts.

If it is dirty in there, it might not be moving quite as well as it should.

Like I said, take it apart and clean it. Maybe spray the valve with a little penetrating oil to lube it up/prevent corrosion from cleaning it. It is basically a solenoid valve, so if there is too much gunk, it can make it drag. You can use a small pry tool, and carefully slide it open to clean the passage way out.

Is this a 100% guarantee it will cure it? Nope, but it can't hurt to try. It is simple and cheap to do.

https://www.youtube.com/watch?v=F5hQNRNiVQ8
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2001 neon ES MTX with '02 R/T PCM
1999 neon 2.4 EDZ MTX
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Dillmiester
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Age: 28
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2000 Plymouth Neon LX

Post: #7   PostPosted: Wed Feb 08, 2017 11:58 am    Post subject: Reply with quote

It seems to do it more when its hotter outside, its been a little cooler here in Florida but today is on the warmer side and I noticed it doing it when I was sitting at a light.  

Forgot to mention I've also changed the ambient temp sensor. Also rewired connections from Alternator, Starter, and PDC with new grounds.


I've also noticed going from park or neutral and back does sometimes raise the rpm back temporarily but you've probably noticed it sinks back into it again. I tend to think its something in the factory tune more than anything.

I'm thinking its only in closed loop it does this I've never really thought about it till this came back up.


*Edit

Took some more readings today while in drive lowest I saw it hit was 756. Peaks a little over 900 momentarily after switching from park and settles to around 820-880. 
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BlackRoseRacing
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Age: 38
Joined: 25 Dec 2004
Posts: 12696


2002 Dodge Neon R/T

Post: #8   PostPosted: Thu Feb 09, 2017 8:03 pm    Post subject: Reply with quote

I'd look into the IAC motor to see if there is any issues there. It should be 2 8 or 10mm screws holding it on. Pop it off real quick to see if there's any carbon build up in there.

[url] https://www.stockwiseauto.com/airtex-2h1088-idle-air-control-valve?Year=2004&Make=Dodge&Model=Neon[/url]

^^^^this link will show you what the IAC looks like
Also without getting crazy and scientific, when you have the IAC removed keep it plugged in and have someone turn the key on so you can watch the movement of the IAC motor. This way you can make sure its opening and closing properly.
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shifted92
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Post: #9   PostPosted: Wed Mar 29, 2017 10:45 pm    Post subject: Reply with quote

Did you ever figured it out or fixed it? IAC motor is worth checking, we experienced some issue due to carbon build up there.
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