Hi guys, I know this topic has come up before, but it's just strange in my case (so I think).

Current situation, once the car is warmed up all the way and you come to a stop (at a light/sign), in most cases the idle will hit about 800 for half a second, then slowly drop down to 550-600. That idle is low for my car and it shakes the whole car noticeably.

My car never did this until about 6 months ago. I took it in to have the struts replaced (over 100k, never had them done before). They also replaced the motor mounts (had a broken one), water pump, and timing belt (they were all due and I knew about them prior to going in). Ever since then, it's been happening. They couldn't figure it out.

I recently had an issue where the car wouldn't start. Took it in and they replaced the IAC valve (it wasn't operating properly) and did some cleaning (intake manifolds, throttle body, idle passages). They thought that would fix the idle issue as well...didn't. They thought it needed to re-learn...didn't (these year cars don't re-learn right...needs software to do that?). They had a software update done to it and thought it would fix it...didn't.

I also recently replaced the plugs/wires as it was due. Same thing happening still.

Any other ideas guys?

Thanks!

Tim

 

My 05 sxt has always idled at around 600 rpm's unless the a/c was on then the idle is about 800-900. I have never had vibrations unless a mount was bad. Wish I could help. Good luck to you. One question though that might help with a diagnosis. The vibration you feel when the rpm's drop, does it last for a little bit then smooth out staying at the 550-600 rpm's, or does the vibration continue the whole time the rpm's are sitting 550-600?

 

Its a neon thing happens alot to neons happens every so often to mine. Dont know about the vibrating mine does vibrating when Im stopped sometimes though.

 

I've read where some Neons have it, but it was just strange that this never happened until I had the work done.

Vibration stays until I step on the gas and push the idle back up to 800+. Only associated with the low idle, it's smooth once the idle goes back up.

 

Don't know if this will help any. But another time when my rpm's would dip low, (lower than the norm for my neon), I also had some hesitation during acceleration that was an intermittant problem. It was under warranty, and the dealer diagnosed the problem as bad spark plug wires. I replaced the wires with those awsome wires from napa called belden. I also decided to replace the coil with an msd one. Can say I have never had that rpm problem again and the hesitation never returned either.

 

have you checked the timing to make sure they didn't put it off by a degree or two?

 

You can take out your old coil and have it checked out at a autozone for free than you can see if thats the problem seeing you did not replace that with the plugs and wires.

 

Hey Wahnsinn, I agree that it is just to strange of a coincidence about these problems coming up just after the timing belt...most likely a timing thing. One other question, when the dealer did the cleaning of the throttle body, etc. did they clean out your fuel rail. My Neon is an asphalt stock car and I clean the fuel rail about once per month. You'd be surprised what crap you'd find in there after a couple of years. Take the rail off and diconnect the hoses, injectors, etc. Spray a bunch of parts cleaner or brake-clean in the rail swish it around really good and dump it out onto a clean white rag or towel. The evidence will show up on the rag. Its somethng pretty easy and quick to try and it helps anyway. Check your injectors' resistance reading (ohms) while you're at it too...just some suggestions.
If you don't have a manual and need the proper range for the ohms reading for your injectors I'll look it up for you. Just let me know.

 

...one othe thing...make sure that your injector ends aren't plugged up with crap as well. Use some brake clean to spary those out too.

 

wouldn't a seafoam treatment do pretty much the same thing without all the hassle?