High RPMs when out of gear. ***FIXED***

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High RPMs when out of gear. ***FIXED***

Post by ZeroChad » Wed Sep 05, 2007 3:22 pm

Hey guys, I've been having this problem with my 02 SE mtx. It has occurred ever since the car was restored, before I put on the CAI. I now have a tach cluster so I can diagnose the problem better.

Basically, when the car is moving above 15mph and I take it out of gear the rpm shoot up or drop down to 2k. this seems a bit high to me for an idling rpm. I was expecting more about 1k which is what it idles at while stationary.

I've already tried testing for vacuum leaks by spraying degreaser on the hoses while the engine is running and looking for rpm changes. Is there a specific area I shoulda been looking for b/c I didnt find anything?

Any other suggestions would be greatly appreciated.


UPDATED late summer:
Ok so I replaced the IAC sensor. The part from eBay was of great quality. Here is a pic showing both next to each other.
Image

This, however, didn't quite fix my problem. Its seems that sometimes my idle will be at 1600 now and other times its back to 2000. :banghead: Keep in mind this is all while the car is moving more than 5mph. Maybe I just need to allow more time for the pcm to reset itself I dunno.

I did notice that on the throttle body I did have the "tube" mentioned in the below post w/o a cap on it. This however, is before the throttle plate so there shouldn't be any vacuum lose. I'm gunna tape it up to be on the safe side.
http://forum.2gn.org/viewtopic.php?t=25 ... e+body+cap
Image
The tube is to the right of that sticker.

Also, I've attempted to get the codes to come on my odometer, keep in mind I'm not throwing a CEL. I haven't had any luck so far, and it hasn't shown a "done" either.

Anymore ideas would be appreciated. I'm thinking about just getting a replacment 60mm TB.

UPDATED: 10-19-07
A while ago, when I was changing my spark plugs, I noticed that I had a lot of oil on the third plug wire and top of the plug. :pukeleft: I realize from using the search button :-) that this means I need new spark plug gaskets, which come with the valve cover set.

So I thought "hey what a perfect excuse to buy a Mancini powder coated VC." I know the gasket is what is wrong here, but do you think the faulty gasket could be causing my vacuum problems?

UPDATED 12-10-07
Could this be caused by an improper reading from my TPS? I also remember reading a post about someone having rpm issues over a weak spring in there throttle body.

I've noticed some interior parts are vibrating now more in the cold @ around 2K RPM, so this is really getting annoying. I've kinda put off looking for vacuum leaks since its so cold out, my last thing to check is the intake manifold and in the rear of the engine. :-/
Last edited by ZeroChad on Mon Jun 16, 2008 1:24 am, edited 8 times in total.
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Post by danman132x » Wed Sep 05, 2007 3:37 pm

I think it's just neons. When I put it in neutral at any speed, the rpm's hover around 1500 (especially with the a/c on) until I come to a complete stop. When I stop, the rpm's return to normal idle around 700-800. I checked for leaks, and can't find any, so I'm assuming this is normal.
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Post by ZeroChad » Thu Sep 06, 2007 9:57 pm

anyone else having this issue?
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Post by 60trim » Thu Sep 06, 2007 10:06 pm

Degreaser won't really do anything. You need Carb Cleaner. Try it again. Check the tube before the intake manifold and after the throttle body. Its called the bellows tube. Sometimes theres a rip in it and you wouldn't notice till later. Let us know what you find.
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Post by Cbussilver01es » Fri Sep 07, 2007 12:28 am

Yea Im having the same problem. Mine comes and goes though, sometimes it does it some times it dont. I guess its just neons...
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Post by OB » Fri Sep 07, 2007 12:37 am

Unfortunatly, the "because it's a neon" excuse doesnt quite cut it in this kind of situation. :) Revs should drop smooth and quick when the clutch is disengaged (taken out of gear) or in neutral. However, when coasting, its normal for idle to be a hair more than it is at a stop. Somewhere between 900-1100 isnt uncommon. If the idle appears to stick in one spot or stay somewhere higher in the rev range (anything over 1200 rpm could be considered high), you're problem may be related to an IAC issue. If not the motor itself, something in the airstream that is causing incorrect input readings to the PCM, therefore resulting in some hesitation returning to idle off throttle.

Does it happen if you rev the engine when parked? I wouldnt doubt that the maps are different when coasting, as a VSS signal is taken into consideration for IAC operation when the car is moving. Having a slightly higher idle when coasting is a way for the PCM to be prepared to resume in-gear operation should the driver need to, without hesitation or bog.
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Post by ZeroChad » Fri Sep 07, 2007 2:15 am

Yeah it does make sense that the engine should be running higher rpms when disengaged and moving. When I rev the engine while stationary, the engine drops back down to normal idle rpm.

It does habitually stick to 2k when I take it out of gear while moving, so an IAC problem would make since. It might have gotten damaged in the accident the previous owner had, though it looks ok. Where exactly does the VSS signal come from?

However, the bellows tube does seem like a good place to double check. Gunna try out some carb cleaner on it this weekend.

Much thanks for all of your input guys!
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Post by OB » Sat Sep 08, 2007 3:43 am

The VSS is mounted on the output shaft of the transaxle. I doubt this is the issue, but its something to look into as a last resort.

Tonight I making a few adjustments to my idle control screw, and I remembered this thread. Try making adjustments in small increments to the screw. It is located below the throttle cable cover on the throttle body (battery side). You can see it with a telescoping mirror, or feel it with your hand. It is adjusted with a 5/32" socket. Try backing it off a half turn or to (counterclockwise) and drive the car. Continue doing this for about 2 full turns.

If the problem is still there, that eliminates the adjustment screw as being the solution. If this is the case, return it to its original position. You want to keep it on the tight side to prevent loss of throttle response and idle quality, so dont over loosen it. It should be right at the threshold. Let me know what happens.
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Post by ZeroChad » Thu Oct 04, 2007 5:33 pm

Well I had some time today to dive into the problem again. After I washed my car I went to town with a can of carb cleaner. Couldn't find any vacuum leaks this time either.

I've also been fiddling with that idle control screw. It brings down the idle a little, but not quite the fix I was looking for.

Perhaps it is an IAC sensor problem. Are those expensive to replace?
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Post by Adionik » Thu Oct 04, 2007 5:37 pm

Mine does that same stupid shit, but ONLY with my 60MM tb. The stock TB doesn't have that problem. I'm guessing this has to do with the IAC sensor and the proper seal...i'm going to put some more silicone around it when I get home tonight and attempt to fix it. It seems to be staying in the higher RPM's when i'm driving as well...not dropping as quickly as i'd like.

I'm with ya...i'll let you know what i find.
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Post by occasional demons » Fri Oct 05, 2007 12:16 am

Got a new OEM AIC from here: http://cgi.ebay.com/ebaymotors/Dodge-Ne ... 0159336141

It is a factory piece w/Mopar number in the plastic just like the original. My idle is normal now exect the RPMs still hang @ coasting, will have to see if this goes away as the PCM resets. Maybe it's supposed to do this and mine was just "bad" and idled "normal" @ coast before. Time will tell. If someone could combine these posts that would be great, if it's OK with ZeroChad.
BTW stealer list is $135 and local parts stores around here are $140-$164! The ebay one is a damn good deal, especially if you want an extra one to go with 60mm TB.
Copied and pasted from my thread.
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Post by ZeroChad » Fri Oct 05, 2007 12:43 pm

I'm all for combining em.

BTW thanks for the link. Ebay can be a wonderful place.
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Post by occasional demons » Fri Oct 05, 2007 4:56 pm

"Ebay can be a wonderful place"

Yes it is. I really didn't want to spend $135.00 + tax at the dealer and find out my PCM was the problem! But luck was with me and it was the AIC. :rockon:
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Post by ZeroChad » Sat Oct 13, 2007 12:39 pm

UPDATE: received the sensor today. Should be able to install it in a few hours. Wish me luck.

Oh btw, to reset the computer I just just need to unhook the battery for a little while right?
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Post by 01NeonSnooZer » Sat Oct 13, 2007 2:28 pm

I'f that doesn't help, pull the DTCs and see what they are. Look for a code that says something along the lines of "MAP input out of range" or something like that. Check ALL of the codes, don't just single that one out. I forget ow to make the instrument cluster flash the codes out, though. Can someone tell him how to da that?
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Post by occasional demons » Sat Oct 13, 2007 4:57 pm

01NeonSnooZer wrote:I'f that doesn't help, pull the DTCs and see what they are. Look for a code that says something along the lines of "MAP input out of range" or something like that. Check ALL of the codes, don't just single that one out. I forget ow to make the instrument cluster flash the codes out, though. Can someone tell him how to da that?
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Post by ZeroChad » Sun Oct 14, 2007 1:27 pm

updated
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Post by occasional demons » Mon Oct 15, 2007 12:17 pm

Mine took a day or two to settle down after I replaced the AIC. But the fact that you're not getting any response from the Odometer readout could be another issue.... A 60mm wont cure the idle problem as you have to use the same AIC that you have.
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Post by Kelevra » Mon Oct 15, 2007 1:31 pm

damn, ur idling around 1600-2000?? holy shit. Mine idles at 550-700 when in gear at a stop and about 600-750 when in nuetral

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Post by ZeroChad » Mon Oct 15, 2007 6:23 pm

occasional demons wrote: A 60mm wont cure the idle problem as you have to use the same AIC that you have.
I guess I worded that wrong. I mean in the near future I'll be getting one, so I'll continue looking elsewhere. I'm thinking its probably a vacuum leak... hmm. Gunna check the bellows tube again. Though it might drop down these next couple of days with the new IAC, you never know.

Kelevra wrote: damn, ur idling around 1600-2000?? holy shit. Mine idles at 550-700 when in gear at a stop and about 600-750 when in nuetral
Yeah its only when I take it out of gear while moving though. It should drop down, but doesn't. It'd be so much easy to diagnose if it did it at a stop as well.
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Post by Kelevra » Mon Oct 15, 2007 7:16 pm

well, when i put her in neutral when I'm going down the road it's at about 900-1250

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Post by ZeroChad » Fri Oct 19, 2007 4:34 pm

A while ago, when I was changing my spark plugs, I noticed that I had a lot of oil on the third plug wire and top of the plug. :pukeleft: I realize from using the search button :-) that this means I need new spark plug gaskets, which come with the valve cover set.

So I thought "hey what a perfect excuse to buy a Mancini powder coated VC."

I know the seals and gasket are what is wrong here, not the valve cover, but do you think the faulty gasket could be causing my vacuum problems?
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Post by aperson » Fri Oct 19, 2007 5:07 pm

There isn't any vacuum there so no. But my ATX sits right around 800-900 RPM in neutral, could be an MTX thing.
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Post by Adionik » Fri Oct 19, 2007 7:01 pm

Check your coil catch can!
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Post by fixitmattman » Fri Oct 19, 2007 7:50 pm

Do you run with the AC / defrost on frequently? When the compressor is on the idle will remain high like that when it's out of gear for a few seconds, but should still drop down. If it keeps holding at higher RPM you've got a vac leak somewhere.
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Post by occasional demons » Fri Oct 19, 2007 10:12 pm

I was thinking about the higher idle when moving, it's possibly designed to idle a little higher so the engine doesn't stall resulting in loss of control due to increased steering effort. But over 1200 RPM would be too much. The engine dying while moving seems to be the #1 complaint in some consumer reports I've been reading...
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Post by ZeroChad » Sat Oct 20, 2007 12:17 am

Adionik wrote:Check your coil catch can!
Unfortunately I don't have one yet, but in the near future I will. How much oil do you find in there a month?
fixitmattman wrote:Do you run with the AC / defrost on frequently? When the compressor is on the idle will remain high like that when it's out of gear for a few seconds, but should still drop down. If it keeps holding at higher RPM you've got a vac leak somewhere.
Nope, don't ever hardly use em. Any suggestions on a possible vacuum leak area? I've scowered the engine bay, but haven't found anything yet.
I was thinking about the higher idle when moving, it's possibly designed to idle a little higher so the engine doesn't stall resulting in loss of control due to increased steering effort. But over 1200 RPM would be too much. The engine dying while moving seems to be the #1 complaint in some consumer reports I've been reading...
Lol I think my pcm has been reading consumer reports too much and wants to keep my engine from shutting off.
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Post by fixitmattman » Sat Oct 20, 2007 2:28 am

ZeroChad wrote:Any suggestions on a possible vacuum leak area? I've scowered the engine bay, but haven't found anything yet.
How about checking everything from the intake manifold to the TB for leaks. May require the removal of the intake manifold. Check the rubber seals between the plastic intake manny and the head.
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Post by ZeroChad » Mon Dec 10, 2007 7:18 pm

Could this be caused by an improper reading from my TPS? I also remember reading a post about someone having rpm issues over a weak spring in there throttle body.

I've noticed some interior parts are vibrating now more in the cold @ around 2K RPM, so this is really getting annoying. I've kinda put off looking for vacuum leaks since its so cold out, my last thing to check is the intake manifold and in the rear of the engine. :-/ How reliable are the intake manifold gaskets?
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Post by ZeroChad » Mon Jun 16, 2008 1:34 am

Well its fixed. Hell yeah! I swapped out my intake manifold with a magnum one and bellows tube. No more idle problem.

Just to let people know it was most likely the ring gaskets on the plastic manifold causing the leak. The manifold itself looked fine. The bellows tube looked good as well. I had checked those connections before, so it probably wasn't them.

Thanks for all the help anyway. What a relief.
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