The famous Neon rough idle question...

The famous Neon rough idle question... - 06/12/14 10:59 PM

I recently had a new timing belt, tensioner, and water pump replaced on my 2001 Neon.

It was discovered that 2 motor mounts were shot, so I had them replaced.

It idles much more rough now (vibration transferred to the car instead of bouncing around on a broken rubber mount). I also changed the plugs and wires, but no difference. There are no codes being thrown.

It does not matter if the a/c is on or not. It does mellow a bit if I put it in park or neutral.

I have searched and read many things online about NEON�s and their rough idle, but I have not yet found an adequate answer or fix (if there is such a thing) for this.

There are many theories, ideas, and folklore out there, but nowhere could I find an actual �Hey, I did this and now it�s back to normal!�

So my question: Who has had a neon rough idle (as described) and was actually able to fix it?

I can live with it, but it would be better if it was a smoother experience when sitting in traffic.

Thanks!

Eightlitermopar

Posted By: Twisted

Re: The famous Neon rough idle question... - 06/12/14 11:19 PM

When I did that work to mine plus the head gasket it was real rough until the computer finished relearning. Battery had been disconnected for a while and it seemed to take about a week to smooth out. I did use the Prothane race inserts though and thought that was the cause of the vibration but it settled down to just a little rougher than factory. I would also check the upper mount to make sure it is adjusted properly, can't remember the measurement off hand though.

Posted By: DaveRS23

Re: The famous Neon rough idle question... - 06/13/14 01:06 AM

I always start by blocking the EGR. It often sticks open and the idle gets rough or even dies. Other than that the car will run fine.

I usually cut up a soda can to temporarily block the EGR off.

Posted By: Supercuda

Re: The famous Neon rough idle question... - 06/13/14 01:14 AM

Quote:

I always start by blocking the EGR. It often sticks open and the idle gets rough or even dies. Other than that the car will run fine.

I usually cut up a soda can to temporarily block the EGR off.

Ding, had the same issue with my 96. If you carefully clean the valve part in lacquer thinner and do not get any of it on/in the vacuum pot you can usually save it rather than paying big money for a new one.

Posted By: eightlitermopar

Re: The famous Neon rough idle question... - 06/13/14 04:04 AM

I checked the adjustment on the upper mount. It was dead on 4.70 inches.

I have also read conflicting reports on an EGR valve on a 2001 Neon.

The rumor is: None of the 2nd Generation neons have an EGR.

Then I heard SOME of the 2001 neons have it. I checked under the hood and couldn't see anything like it, but I could be wrong.

I'm hoping the engine is just relearning and will smooth out a bit.

Any other thoughts?

I also heard a rumor that factory mounts were liquid filled, and the changed to aftermarket makes it more harsh since it is solid rubber?

Posted By: ahy

Re: The famous Neon rough idle question... - 06/13/14 05:19 AM

The idle on my (departed) gen II got rough and slow. It was a gunked up idle circuit in the TB... apparently a common problem fixed by the dealer with some carb clean. My gen I (still running) never had that problem.

Posted By: eightlitermopar

Re: The famous Neon rough idle question... - 06/13/14 05:37 AM

Quote:

The idle on my (departed) gen II got rough and slow. It was a gunked up idle circuit in the TB... apparently a common problem fixed by the dealer with some carb clean. My gen I (still running) never had that problem.

I had heard that too....I may just have to poke around and do some cleaning..... Thanks for the reminder!

Posted By: mopars4ever

Re: The famous Neon rough idle question... - 06/13/14 08:23 AM

has it idled rough since the timing belt change? it may be off a tooth.

Posted By: eightlitermopar

Re: The famous Neon rough idle question... - 06/13/14 01:22 PM

Quote:

has it idled rough since the timing belt change? it may be off a tooth.

I had the same thought, but from what I have read, one tooth off is enough to throw a code. It still has good "power" (by Neon's standard), starts quickly without a fuss, etc.

It had a little shake before, but the motor mounts were shot, so I probably wasn't feeling it....

I can live with it.....it's just one of those little things I wish I had the answer to...

Posted By: gdonovan

Re: The famous Neon rough idle question... - 06/13/14 01:39 PM

One of the things we ran into at the dealer was rust from inside the fuel rail crapping up the injectors causing a rough idle.

Posted By: 360view

Re: The famous Neon rough idle question... - 06/13/14 02:08 PM

Did other Chrysler engines have fuel rails that would internally rust, maybe early 3.9/5.2/5.9 Magnum v8s?

Do the rust particles get caught by the injector top screen baskets?

Posted By: gdonovan

Re: The famous Neon rough idle question... - 06/13/14 02:24 PM

Quote:

Did other Chrysler engines have fuel rails that would internally rust, maybe early 3.9/5.2/5.9 Magnum v8s?

Never run into it as a problem (magnum engines) at the dealership.

4 cylinders are going to be more sensitive to the problem then 6 or 8.

Sometime you could bang the debris out of the injector screen but not always.

Posted By: 360view

Re: The famous Neon rough idle question... - 06/13/14 02:32 PM

Thanks

Posted By: Magnum

Re: The famous Neon rough idle question... - 06/13/14 04:11 PM

Did they ever idle dead smooth?

Posted By: gdonovan

Re: The famous Neon rough idle question... - 06/13/14 04:22 PM

Quote:

Did they ever idle dead smooth?

My 2001 is pretty good.

Posted By: Twisted

Re: The famous Neon rough idle question... - 06/13/14 05:42 PM

Yea, was going to mention that but was focused on the vibration. I have to clean my IAC about once a year. I usually just doing it when I clean my K&N since I am in there anyway. I know the autos are a little rougher and could be the tranny mount or even the torque converter causing. Just as a follow up, if you are using a lot more fuel then it is probably learning. I dropped about 5mpg, it was like running e-85 mileage.

Posted By: That AMC Guy

Re: The famous Neon rough idle question... - 06/14/14 01:50 AM

Did you compare the old mounts vs. the new? I ran into the same situation with my Daytona. Side mount was completely torn, engine mount ripped and trans. mount twisted badly. Replaced them all.

The 2.2's usually idle a bit rough, but mine was like a diesel! I double checked to ensure the engine was level & center and it was fine. It wasn't until I compared the old mounts to the new.

The new are virtually solid. The old ones, the pin in the middle of the mount is suspended by four pieces of rubber. On the new, it's cast right into a block of rubber.

Over time, the harshness has diminished. I think as the rubber breaks in, it allows a little more flex.

Posted By: eightlitermopar

Re: The famous Neon rough idle question... - 06/14/14 04:08 AM

Quote:

Did they ever idle dead smooth?

Quote:

Did you compare the old mounts vs. the new? I ran into the same situation with my Daytona. Side mount was completely torn, engine mount ripped and trans. mount twisted badly. Replaced them all.

My neon was pretty smooth since I bought it in 2004. Recently I had started to notice a �clunk� when the tranny shifted. I figured the mounts were on their way out which was confirmed when the timing belt work was being done. This is why I did it all at once. Since the mounts have been fixed, no clunk, just the vibration or mild shudder when stopped, engine running, in gear. Neutral or park does mellow it out just a little.

Quote:

Yea, was going to mention that but was focused on the vibration. I have to clean my IAC about once a year. I usually just doing it when I clean my K&N since I am in there anyway. I know the autos are a little rougher and could be the tranny mount or even the torque converter causing. Just as a follow up, if you are using a lot more fuel then it is probably learning. I dropped about 5mpg, it was like running e-85 mileage.

I have never cleaned the IAC to be honest. EDIT: I just looked it up and it doesn't seem too difficult to remove. I may do that tomorrow and clean it up. I'll keep you posted and let everyone know if it actually makes a difference.

Quote:

One of the things we ran into at the dealer was rust from inside the fuel rail crapping up the injectors causing a rough idle.

Now this intrigues me�. Did you have to replace the rail or just clean it out? Are you saying the rust particles were wedged into the injector itself or the rail? Did this usually mean injector replacements?

This small issue isn�t a deal breaker with my neon; I plan on keeping it a long time. It�s just annoying is all�.

Thanks for the replies guys!

Posted By: gdonovan

Re: The famous Neon rough idle question... - 06/14/14 12:29 PM

Usually we would replace the rail, if it was under warranty we would just replace all of it since Mopar was paying the bill.

Once the rail starts going it isn't going to stop.

Posted By: eightlitermopar

Re: The famous Neon rough idle question... - 06/14/14 05:20 PM

Quote:

Usually we would replace the rail, if it was under warranty we would just replace all of it since Mopar was paying the bill.

Once the rail starts going it isn't going to stop.

Hmm....sounds expensive since I don't have a warranty.

Today I will try cleaning the IAC first and cleaning the throttle body with TB friendly cleaner.

The next step after that I will take the rail off and start poking around there to see what I find. I will post pics if anything looks weird.

Could you actually see rust particles in the injector? Or were they just to small and wedged down there?

Any other thoughts of where I could try looking?

Thanks again! It would be sweet if I had the only complete answer on the internet how to fix this problem. It is a challenge now!

eightlitermopar

Posted By: eightlitermopar

Re: The famous Neon rough idle question... - 06/14/14 07:36 PM

So I took off the IAC, and it actually looks pretty clean. If I wanted to clean it out, do I just spray brake cleaner in the hole to the left? I don't want to ruin anything...

Attached picture 8176105-DSCN0348.JPG

Posted By: eightlitermopar

Re: The famous Neon rough idle question... - 06/14/14 07:39 PM

Also, while I was poking around, I noticed the plug on one of the vacuum ports. You can see which port I am talking about in the picture.

Attached picture 8176107-DSCN0350.JPG

Posted By: eightlitermopar

Re: The famous Neon rough idle question... - 06/14/14 07:40 PM

Here is the plug that was covering it.....

Posted By: eightlitermopar

Re: The famous Neon rough idle question... - 06/14/14 07:41 PM

another view

Attached picture 8176111-DSCN0352.JPG

Posted By: Twisted

Re: The famous Neon rough idle question... - 06/14/14 09:28 PM

Just spray everything including the TB side. I have connected power to actuate the valve but it doesn't seem needed if it seems to be working, just spray both sides. Not sure on that cap. It could be a problem but I would think it would be more noticeable of a stumble if it had a vacuum leak.

Posted By: eightlitermopar

Re: The famous Neon rough idle question... - 06/15/14 12:16 AM

Quote:

Just spray everything including the TB side. I have connected power to actuate the valve but it doesn't seem needed if it seems to be working, just spray both sides. Not sure on that cap. It could be a problem but I would think it would be more noticeable of a stumble if it had a vacuum leak.

I haven't sprayed the throttle body or the IAC yet, I wanted to see what difference the new vacuum cap made.

Before I was idling (in gear) at about 600 rpm (according to the dash tach).

I put on a good plug and now I am idling about 800, so some of a difference there, but the rough idle "shudder" is still there.

I will keep playing around and keep you guys posted.

eightlitermopar

Posted By: gdonovan

Re: The famous Neon rough idle question... - 06/15/14 11:57 AM

Quote:

Could you actually see rust particles in the injector? Or were they just to small and wedged down there?

One way to tell is the spray pattern on the injectors.

Posted By: DaveRS23

Re: The famous Neon rough idle question... - 06/15/14 06:22 PM

In my experience, when the IAC is dirty the idle is slow to respond or unresponsive. As in idles too high or the engine dies at idle because it is too low. The IAC is just a tapered plunger that plugs and unplugs a by-pass hole in the throttle body that allows more or less air into the engine.

It doesn't usually cause a rough running idle condition, unless it causes an extremely low idle that causes the engine to shake.

I usually spray carb cleaner in it and let it soak for awhile and then spray it again. Be sure to remove the gasket/seal first.

Posted By: Todd

Re: The famous Neon rough idle question... - 06/15/14 06:32 PM

Where I work we have BG induction service.
It has an injector that sprays cleaner in the t-body with the engine running.
Works very well. Cleans the entire t-body,IAC circuts and intake.
I had a neon I did that to and the inside of the intake looked like new.
I clean all my vehicles every 30k with it.

Posted By: 71yelladustr

Re: The famous Neon rough idle question... - 06/15/14 10:10 PM

You might check to see if you have plenty of clearance between the core support and the engine and trans. I have seen alot of neons that have bottomed out at some time or another and pushed the core support back into the engine of trans. Especially the second gen cars. The The PCM and rad fans like to come in contact with the trans causing the issue you describe. One other thing, Have you ever done a compression test on your engine? Later 2.0s had horrible valve jobs and are common for the valves not to seat well and cause miss or shake without setting a MIL.

Posted By: eightlitermopar

Re: The famous Neon rough idle question... - 06/16/14 01:22 AM

Quote:

You might check to see if you have plenty of clearance between the core support and the engine and trans. I have seen alot of neons that have bottomed out at some time or another and pushed the core support back into the engine of trans. Especially the second gen cars. The The PCM and rad fans like to come in contact with the trans causing the issue you describe. One other thing, Have you ever done a compression test on your engine? Later 2.0s had horrible valve jobs and are common for the valves not to seat well and cause miss or shake without setting a MIL.

I have not checked the compression yet, mostly because I am afraid I am going to find a low cylinder. I have heard that about these cars as well. Also, the car drives great (other than the idle, which isn't horrible) and it gets great mileage, so even if I have a dead cylinder....I probably wouldn't do anything about it anyway

Posted By: 383man

Re: The famous Neon rough idle question... - 06/16/14 07:58 AM

Quote:

In my experience, when the IAC is dirty the idle is slow to respond or unresponsive. As in idles too high or the engine dies at idle because it is too low. The IAC is just a tapered plunger that plugs and unplugs a by-pass hole in the throttle body that allows more or less air into the engine.

It doesn't usually cause a rough running idle condition, unless it causes an extremely low idle that causes the engine to shake.

I usually spray carb cleaner in it and let it soak for awhile and then spray it again. Be sure to remove the gasket/seal first.

I agree as a dirty IAC wont cause a rough idle just a slow or fast idle. My question is does it feel like a dead miss or more like a vibration but still hitting on all 4 cylinders ? Ron

Posted By: Grizzly

Re: The famous Neon rough idle question... - 06/16/14 05:43 PM

I feel your pain, Eightliter, I am pulling my hair out with the same problem for the last 2 months.

And, just like you, I found a lot of suggestions but no real solution with Google.

One, that will be a last resort, is a fellow drilled a 5/32nd hole in his throttle plate.

I just had a Dealer re-flash done on the car as per a TSB for "rough idle, P0300 random misfire" issues. It didn't help, but the misfire codes don't show up as much.

Still getting P0300 and P0301. Have swapped wires, plugs, tested the coil, checked wiring harness to coil, changed the IAC, and just last night I took all the injectors out and cleaned them off the car (pretty neat method I found online

).

Unhooked the battery, cleared the codes, and fired it back up. Ran smooth and figured I got it. Drove it a few minutes, stopped in Drive, and the miss/low idle is back.

This little issue has really soured my high praise for Chrysler. The thing has low miles, well-cared for, drives/handles, just generally does everything better than any brand-x vehicle otherwise.

I did the timing belt, crank seal, and cam seal and was very careful on getting the timing marks correct. The car ran perfect for a few thousand miles and then the misfire codes came up.

Some great suggestions on here too, thanks Guys, I'll give them a try. I guess I gotta find some time this week and dig into it again.

Posted By: therocks

Re: The famous Neon rough idle question... - 06/16/14 05:56 PM

What pluigs and wires did you use?I had one at work that I used Champions in that were direct replacement.It would run great but had rough idle at times.Changed them and wires twice.Finally I had the manager get Champions from the dealer.Installed them and no more roughness.Weird I know as they were the same plug and number.Wires will cause a rough idle and sometimes a miss also.The wifes PT went thru it.New Autolite wires 2 sets.New plugs 3 sets.Id pull number 1 and it would have a track on the porcelian.It wasnt much.I finally used Advanced wires 2 years ago.No more rough idle or occasional miss.Rocky

Posted By: gdonovan

Re: The famous Neon rough idle question... - 06/16/14 06:09 PM

Quote:

I did the timing belt, crank seal, and cam seal and was very careful on getting the timing marks correct. The car ran perfect for a few thousand miles and then the misfire codes came up.

We did coil packs like popcorn too, it was such a noted issue that I still have a test coilpack that was in my toolbox for down and dirty testing.

Posted By: Grizzly

Re: The famous Neon rough idle question... - 06/16/14 06:41 PM

Rocky, I went to an NGK. The gap on them has opened a bit but nothing too crazy. They have probably 15, 20,000 miles on them is all.

I saved the old Champions and threw it back in #1 hole and it still has the miss.

I have heard over the years the only thing a Dodge likes is Champions. I found that out too with 360 Magnum: tried NGK's and wound up going back to Champions.

Swapped the 1 and 4 wire and still missfire on #1. I swapped the #1 and #2 injector last night, we'll see what happens after it gets some miles on it.

Posted By: gdonovan

Re: The famous Neon rough idle question... - 06/16/14 06:54 PM

Quote:

I have heard over the years the only thing a Dodge likes is Champions. I found that out too with 360 Magnum: tried NGK's and wound up going back to Champions.

Normally I run nothing but Champions, but have Autolights from Wally-world in the neon 3 or 4 years ago and it didn't seem to care.

Still running great.

The coil pack on your car might have a carbon track on it, wasn't unusual at all.

Posted By: therocks

Re: The famous Neon rough idle question... - 06/16/14 08:16 PM

We run NGKs in everything.I always ran Autolites.Then I went NGK in the 440 with 12.5 compression and street driven.It really likes them as does the other cars.Even the PT likes them.The 440s have been in about 4 years and still no problems.The Autolite race plugs always had a slight off sound.Rocky

Posted By: eightlitermopar

Re: The famous Neon rough idle question... - 06/17/14 06:45 AM

Sorry for the delayed update.

It seems to run fine, just that "shudder" at idle. No codes are being thrown.

Plugs and wires changed as stated. I replaced the plugs with original champions (from NAPA), and MOPAR wires from the dealership.

It did not run any better or worse after the swap. I noticed it fired quicker with the new plugs, not as much cranking.

I'll have to check my coil pack too, and I still have to check the resistance on my injectors.

Posted By: Grizzly

Re: The famous Neon rough idle question... - 06/17/14 02:41 PM

Quote:

...........I'll have to check my coil pack too, and I still have to check the resistance on my injectors.

I had 12.4 to 12.7 Ohm all the way across on mine.

Injector Testing

Also, in that troubleshooting series I used their method for testing the coil:

Coil Test

Had a nice, fat spark.

I pulled all the plugs last night and tightened the gap to .30: run it again for awhile and see what happens.

Good luck.

I'm still thinking about drilling the hole in the throttle plate....

Posted By: DaveRS23

Re: The famous Neon rough idle question... - 06/17/14 02:56 PM

Quote:

Quote:

...........I'll have to check my coil pack too, and I still have to check the resistance on my injectors.

I had 12.4 to 12.7 Ohm all the way across on mine.

Injector Testing

Also, in that troubleshooting series I used their method for testing the coil:

Coil Test

Had a nice, fat spark.

I pulled all the plugs last night and tightened the gap to .30: run it again for awhile and see what happens.

Good luck.

I'm still thinking about drilling the hole in the throttle plate....

Something to think about; The computer is always trying to hit the programmed idle speed and uses both air flow and timing to get there. If you drill the plate allowing more air in and the computer can't control the idle with the IAC, it will do it with timing. So it could pull too much timing out at idle.

Less timing at idle may not be a good thing.

Posted By: Supercuda

Re: The famous Neon rough idle question... - 06/17/14 03:31 PM

My question is, did you reset the computer after you fixed the vacuum leak?

Posted By: demon440

Re: The famous Neon rough idle question... - 06/17/14 06:02 PM

I have an 04 Neon with 95,000. miles
I am the original owner. This car had a rough idle since day 1. Dealer told me it's normal.
Recently it has a bad stumble, almost like it cuts out. In the past I have put 2 MSD coils on it and changed plugs and wires. Recently replaced
the solenoid on the fire wall for emissions but that didn't help.

Posted By: eightlitermopar

Re: The famous Neon rough idle question... - 06/21/14 09:22 AM

Quick update. I have done nothing but drive the car

Seriously though, I didn't know if the car was relearning or not after being in the shop. I put some Lucas injector cleaner in and have been driving it.

Idle still hovers about 600-800 RPM, starts right up and drives fine.

I guess I can't complain though. I have seen some 4 cylinder cars shake so bad at idle you would think it had an uneven washing machine running under the hood.

I do want to do a compression test though just for kicks. I will post the results as soon as I get them.

eightlitermopar

Posted By: moparmikethree

Re: The famous Neon rough idle question... - 06/22/14 04:19 AM

Have the timing belt rechecked. It is off a tooth on the can sprockets

Posted By: Yellow Fever

Re: The famous Neon rough idle question... - 06/22/14 04:26 AM

Quote:

I have an 04 Neon with 95,000. miles
I am the original owner. This car had a rough idle since day 1. Dealer told me it's normal.
Recently it has a bad stumble, almost like it cuts out. In the past I have put 2 MSD coils on it and changed plugs and wires. Recently replaced
the solenoid on the fire wall for emissions but that didn't help.

Do the timing belt, water pump and tensioner if you haven't yet! It will bend valves if it breaks!!

Posted By: eightlitermopar

Re: The famous Neon rough idle question... - 06/22/14 05:45 PM

Quote:

Have the timing belt rechecked. It is off a tooth on the can sprockets

I thought of this, but I understand that if it is off 1 tooth it will throw a code

Posted By: 360view

Re: The famous Neon rough idle question... - 06/22/14 06:35 PM

You might try directing some propane from an unlit torch into the intake to the air filter after the engine is fully warmed up.
(when started cold the air fuel ratio is very rich anyway)

If one or more of your fuel injector tips have deposit build ups interfering with the short solenoid plunger up down at idle, the extra propane should smooth out the idle.

If the IAC is working correctly it should adjust while this is happening and RPM should keep returning to spec as the propane is quickly added or taken away.

While you have the propane torch out check for air leaking past gaskets or o- rings.r

Carbon deposits on the backsides of intake valves can also cause a rough idle.

If you are going to keep driving it
add a bottle of Chevron Techron Plus to your next tank,
a bottle of Gumout Regane to the 2nd tank,
then a bottle of Redline SI-1 to the third tank.

This is about the cheapest thing you can do
considering the cost of man-hrs
and based on the idea that:
"what one cleaner cannot dissolve, another one might".

Posted By: eightlitermopar

Re: The famous Neon rough idle question... - 06/23/14 03:48 AM

Quote:

You might try directing some propane from an unlit torch into the intake to the air filter after the engine is fully warmed up.
(when started cold the air fuel ratio is very rich anyway)

If one or more of your fuel injector tips have deposit build ups interfering with the short solenoid plunger up down at idle, the extra propane should smooth out the idle.

If the IAC is working correctly it should adjust while this is happening and RPM should keep returning to spec as the propane is quickly added or taken away.

While you have the propane torch out check for air leaking past gaskets or o- rings.r

Carbon deposits on the backsides of intake valves can also cause a rough idle.

If you are going to keep driving it
add a bottle of Chevron Techron Plus to your next tank,
a bottle of Gumout Regane to the 2nd tank,
then a bottle of Redline SI-1 to the third tank.

This is about the cheapest thing you can do
considering the cost of man-hrs
and based on the idea that:
"what one cleaner cannot dissolve, another one might".

The car runs great above 800 RPM. I will try some of the additives to see if that helps.

I'll let you know if anything changes, but I am accepting the fact that I just might have a slightly rough idle for the rest of the days I own this car. With the cost of cars going up and up, I plan on driving this car into the ground.

Posted By: eightlitermopar

Re: The famous Neon rough idle question... - 07/08/14 07:24 PM

So, here is my latest update.

The car was running very rough at idle and seems to be getting worse. When the car is in �drive� at idle, it started developing a loud �chirping� sound that gradually got louder.

I took it back to the shop that did the timing belt, water pump, and replaced 2 motor mounts.

Long story short: The new motor mount/strut on the passenger side of the motor was adjusted properly (front to back), but the adjustment (side to side) was a little close to the motor. It was just enough that the idle would cause it to make contact and really vibrate the car.

After a readjustment, it idles A LOT smoother. However, there still is a bit of a shake at idle, but nothing close to what it was. They claim that if I replaced all of the mounts, it would smooth out like a new neon.

Based on what I experienced just with just one properly adjusted mount/strut, I totally believe it.