Would this MP product fix our bad idle problems?

titansxt · Post by **titansxt** » Mon Aug 08, 2011 4:38 pm

http://www.modernperformance.com/manual ... -2004.html

I know it says it is just for modified cars but I am sick of my 500 or less idle at stops lights. The car shakes almost as hard as my SRT with solid mounts yet it is all factory.

Any input?

Donkeypuncher · Post by **Donkeypuncher** » Mon Aug 08, 2011 5:46 pm

Or you could drill a hole in the TB butterfly plate. Was discussed a few years back: viewtopic.php?t=9938

Danteneon · Post by **Danteneon** » Mon Aug 08, 2011 6:02 pm

Or, if you are using a MPx 60mm TB, you can adjust the idle screw just enough so the plate is open slightly bringing your idle up to 750-800rpm (or possibly higher) without the TPS reading above 0. I recently did this and it helped a great deal. No more low idle

Donkeypuncher · Post by **Donkeypuncher** » Mon Aug 08, 2011 9:32 pm

Mine idles right at 800 with the 1/8" hole. It still occasionally drops down to 500 when I stop, but jumps right back up to 800 on it's own.

Post by **occasional demons** » Mon Aug 08, 2011 9:50 pm

That might work on an SRT TB and '00, but I'm not seeing how it would work for the '01 to '05 IAC set up.

magner · Post by **magner** » Tue Aug 09, 2011 4:02 pm

Do you drive you car in the winter or on colder days? Having that will be a nightmare if you do

flhmfd · Post by **flhmfd** » Thu Aug 11, 2011 1:35 pm

should I drill my R/T TB butterfly? I'm sick of this shit already and its been 2 days.

darthroush · Post by **darthroush** » Thu Aug 11, 2011 2:32 pm

I read that TB thread too. I'm considering drilling the plate myself. I adjusted my throttle screw, which helped but seemed to create an extra "drain" on fuel economy, so I put it back best I could (sans tach).

Donkeypuncher · Post by **Donkeypuncher** » Fri Aug 12, 2011 4:27 am

Diablo0 wrote:Actually... according to a very informative lecture I sat through two weeks ago given by Ed Peters a DCx engineer that worked on the Neon project... that screw is only there to adjust the throttle plate enough that it doesn't stick shut when it closes. That's all it's ment to be there for. Adjusting it for idle throws the computer off since when you adjust that screw it gives the computer a mixed signal between the TPS, IAC and MAP sensor when it compares what at each are at to know how much fuel to give the the engine at idle. He highly recommended using about an 1/8" drill bit to drill a hole through the throttle plate instead to keep everything in line.

All I needed to hear is that a DCx engineer that actually worked on the neon project recommended to do it. Haven't had a low idle problem since.

darthroush · Post by **darthroush** » Fri Aug 12, 2011 1:58 pm

I figure worst case, I have to go spend $10 at the JY for a new one...plus the idle screw would be back to exactly where it should.

Donkeypuncher · Post by **Donkeypuncher** » Fri Aug 12, 2011 2:40 pm

You can fill the hole with a plastic weld if it actually comes to that, but I doubt you will ever need to. I felt the same way before I did it, all I could think of is what I had to do if it didn't work.

darthroush · Post by **darthroush** » Fri Aug 12, 2011 6:33 pm

I got a whole list of things to do on the Neon and the Mustang. I finally was able to wash and vacuum the Neon yesterday, as well as get a tire rotation (and get 2 new tires) and PSI check.

I'll add this to the list since I need to kind of go over/clean everything in the engine bay anyways.

OB · Post by OB » Fri Aug 12, 2011 8:44 pm

Those of you with "idle problems". I recommend fixing whatever issue you are having rather than attempt to band aid it with an idle adjustment. These cars don't just develop a low idle, if yours is low then something is wrong and needs to be addressed.

Adjusting the OEM throttle screw will indeed raise idle, however my PCM eventually learned of the new 'base' setting and overrode it by closing the IAC a bit more. Within a couple weeks it was totally back to normal. Adjusted it more, and it figured it out again. This may be NGC only, but I wouldn't be surprised if the older cars PCMs were capable of this as well. The real benefit of the adjustment isn't a higher idle, but improved throttle response .

I wonder if an NGC PCM could compensate for a hole in the throttle plate... Any NGC guys try this?

darthroush · Post by **darthroush** » Sat Aug 13, 2011 5:46 am

I have no idea what is causing my idle problem. I know torque strut inserts cause a transfer of vibration, but my steering wheel still bounces like a jackhammer. I've cleaned the IAC best I could; still does it. All mounts are new and properly aligned and I still have the bad vibration. I've even had the PCM updated to the newest software version that is supposed to have fixed the idle problems...and nothing.

OB · Post by OB » Sat Aug 13, 2011 7:12 pm

A vibration and an idle problem are two different things Ty. My idle is good but the car vibrates like crazy due to mods. MM inserts cause a ton of added vibes, regardless of alignment. Did you measure the torque strut alignment per spec? Trans mount good?

darthroush · Post by **darthroush** » Sat Aug 13, 2011 7:26 pm

I've figured the horrible vibration was from the idle. If I just barely touch the throttle (or increase the idle via the adjustment screw), all of the vibrations go away. I just can't think of anything else except the need for a little extra RPM.

Yes and yes. I've measured with a digital caliper to be as exact as possible (set it to the measurement and locked the slide).

OB · Post by OB » Sun Aug 14, 2011 8:25 pm

Have you used a computer to read the idle revs? Easy way to rule out a low idle issue. These engines naturally vibrate quite a bit at idle, as well as at around 1200 RPM, and a few other sweet spots. You're just feeling it, which is the issue. It still sounds like a mount problem or something along those lines. An out of round component in the rotating assy or tranny will also cause massive vibrations, but usually at more spots in the range than just idle.

darthroush · Post by **darthroush** » Mon Aug 15, 2011 3:53 am

Nope; have nothing of the sorts to hook up to the Neon. It went completely away after my timing belt/water pump/motor mount change and then came back a few days later.

darthroush · Post by **darthroush** » Wed Aug 17, 2011 4:06 pm

Alright. I drilled the 1/8" hole in the TB plate just a bit ago. Took it for a drive and here are my impressions.

Idle in gear, and with the A/C on even, is great. My steering wheel isn't a jackhammer and the entire dash isn't bouncing up and down either. It's way smoother than it was.

The downside though, is that the RPMs don't drop as quickly as they used to when decelerating (let off throttle) and out of gear, the car idles a bit too high IMO. The quirk to this could be though that I installed a higher flow air filter yesterday, but more so, I left the air box lid off. I'm going to put the lid back on, drive it a bit, and see what happens. Perhaps the computer just needs some driving time to adjust whatever it may need to.

EDIT...and the engine almost "diesels" when shutting off because the RPM is so high.

OB · Post by OB » Wed Aug 17, 2011 10:05 pm

It being NGC, I would bet that the PCM will learn to adjust for the hole in the TB plate. Within a few days or maybe weeks, it will slowly reduce IAC flow at idle and during off throttle decel until the target idle is back to normal (or as close as it can get it). This is because the MAP sensor will read a different pressure than 'normal', as compared to the TPS and IAC positions. This is what happened when I adjusted my idle control screw, which is the same as drilling a hole as far as the PCM and it's inputs are concerned. Mine acted exactly as you describe. For awhile, resetting the battery would start the process over again, but it seemed to 'learn' faster each time. When I swapped batteries a couple weeks ago, it didn't revert to the higher idle at all, which tells me the PCM has made LTFT adjustments to accommodate the perceived permanent change in airflow at idle.

Let me know if this ends up being the case, I'm almost certain it will.

Oh, and the reason the vibration improved is because the higher idle pulled the engine out of that particular frequency range. It is basically a band aid fix for the vibration. At any rate, unless confirmed with a scantool (tach is not precise enough), there is no way of knowing if the engine was idling low or not.

Hudson_Neon · Post by **Hudson_Neon** » Wed Aug 17, 2011 11:47 pm

this won't work on 2nd gens. i actually brought it up to Erick the other day to see about possible applications with MS. but the problem is that modern has listed incorrectly. i've already brought it up to their attention

darthroush · Post by **darthroush** » Thu Aug 18, 2011 1:00 am

OB wrote:It being NGC, I would bet that the PCM will learn to adjust for the hole in the TB plate. Within a few days or maybe weeks, it will slowly reduce IAC flow at idle and during off throttle decel until the target idle is back to normal (or as close as it can get it). This is because the MAP sensor will read a different pressure than 'normal', as compared to the TPS and IAC positions. This is what happened when I adjusted my idle control screw, which is the same as drilling a hole as far as the PCM and it's inputs are concerned. Mine acted exactly as you describe. For awhile, resetting the battery would start the process over again, but it seemed to 'learn' faster each time. When I swapped batteries a couple weeks ago, it didn't revert to the higher idle at all, which tells me the PCM has made LTFT adjustments to accommodate the perceived permanent change in airflow at idle.

Let me know if this ends up being the case, I'm almost certain it will.

Oh, and the reason the vibration improved is because the higher idle pulled the engine out of that particular frequency range. It is basically a band aid fix for the vibration. At any rate, unless confirmed with a scantool (tach is not precise enough), there is no way of knowing if the engine was idling low or not.

That's what I'm hoping. I'm going to leave it be for a bit and see what the car decides to do. There is also the possibility that the adjustment screw on the TB isn't quite back to where it was. I'm quite sure it's still a bit farther out than it was.

bone-yard-racing · Post by **bone-yard-racing** » Thu Aug 18, 2011 7:54 am

Manual IAC is a pain it makes it a little like an old dirt bike, get the car started and warmed up now adjust the idle so its correct then drive.

Why are you guys having idle problems?

darthroush · Post by **darthroush** » Thu Sep 01, 2011 4:34 am

How long does it take for the idle to correct itself? I'm still idling high when the engine is warmed up and the transmission is out of gear. In gear, or out with A/C on, it's great.

Post by **occasional demons** » Thu Sep 01, 2011 7:22 am

There is also the possibility that the adjustment screw on the TB isn't quite back to where it was. I'm quite sure it's still a bit farther out than it was.

Have you adjusted the throttle screw back to where it is shut, but doesn't stick when shut?

Usually if I do anything IAC/PCM reset related, it takes a day or two at the most, to settle down.

darthroush · Post by **darthroush** » Thu Sep 01, 2011 11:41 pm

No, I haven't done that yet. I didn't want to mess with that again if I didn't have to. Will do that probably Sunday when I get some time and see what happens then. Thanks!

Donkeypuncher · Post by **Donkeypuncher** » Thu Sep 01, 2011 11:59 pm

I also changed the ground location for the battery and upgraded to 4 gauge wires on all grounds other than the alternator. That seemed to help with the idle dropping out of gear, just seemed to catch the idle faster around 700 rpms or so.

darthroush · Post by **darthroush** » Fri Sep 02, 2011 2:35 am

I've got every ground upgraded to 4g except the alternator as well.