Weird rough idle 2005 Dodge Neon

[97prizm]

Hi ALL,

So I replaced the pcv valve and vacuum line but still get a low/rough idle only when fully warmed up. Shifting into neutral helps Along with having the A/C on. My dad thinks it's a bad vacuum line or leak. Any thoughts or ideas appreciated. I'm beginning to despise Dodge/Fiat quality.

 

[Brian123]

IAC Idle Control Valve!

 

[Imp4]

Originally Posted by Brian123
IAC Idle Control Valve!

$68 on RA...

 

[mk378]

Air leaks anywhere after the MAF will do this. Also dirty MAF. Since it doesn't die when the A/C is turned on, the IAC is likely not stuck closed. Try removing and cleaning it before buying a new one. $68 is a lot to spend on a 2005 Neon that stumbles a little.

 

[Jarlaxle]

Check the IAC...but before you replace it, look carefully for a vacuum leak.

 

[Mad_Hatter]

You already replaced the pcv but..

- make sure you have a clean air filter
- a dirty throttle body can effect idle
- dirty or bad O2 sensor can cause rough idle
- when you're warming up you are in open loop running rich, so that's probably why it only happens when warmed up.. you're in closed loop.
- Look at your fuel trims..if you have a vacuum leak at idle you should have a high (positive) FT. (the effects of even a small vac leak is easily noticable at idle)
- Have you tried running a fuel system cleaner like a Berryman's?

 

[The_Eric]

I don't think there's a maf on this car.. Should be speed density.

Vacuum leaks tend to increase idle RPM, not lower it.

As mentioned, look at fuel trims. If normal, clean the throttle plate and IACV

 

[eljefino]

There's a flexible plastic hose between the throttle body and intake manifold. Check this first!