Not sure where to post this problem. I have a 2004 msm full bolt on ms3pro, E-85 flex fuel, FM intake, dp, ls3 coil kit running sequential, ebc, id 1050s, 36-1 trigger wheel ,lightweight flywheel. The car was tuned by a well known megasquirt shop.I had 10.5 lb flywheel installed shortly before I had the big spark kit installed and tuned. The car runs great with the ls3 coils, can run 15 lbs of boost, and starts up much quicker in cold weather on e-85. Two months after install the car started to get idle droop and stalls, I changed the iacv and the car was running perfect again. Two months later the same thing happens the car first idle droops and searches. I replaced that iacv and tps about 2 months ago, Now getting the same symptoms except The car will start up fine and idle great until it is warmed up going to work ,when the idle dip will appear. Sometimes driving home the idle goes back to the 1000 rpms that it was set at and runs perfect. My tuner has told me that my lightweight flywheel is causing the iacv failures. One other issue is that the car cant hold idle with the ac on when I come to a complete stop, It works fine on the hwy. I am ready to just put in another oem flywheel if that will stop the issues. I am getting both clutch pedal switches, idle switch on the trans and cam and crank sensor installed . Any ideas out there on what the @@@@ is going on with this car?

 

It's idle dip exacerbated by the light weight flywheel causing faster deceleration, and your tune isn't catching it fast enough. There are various methods to try to tune it, but it's generally a very fiddly thing to get right. Try logging and see what's actually happening, but try bumping up the "Accel Pump" (or something like that), set your idle control higher, set your idle VE table richer, etc.

It takes a lot of trial and error, mine is good on E85, but hit and miss on regular. I've tried it on a friend's car too, but it's still hit and miss for him.

But you can also ease it by keeping the clutch engaged and not dropping into neutral until your at your idle RPM, instead of dropping into neutral from a cruise or under breaking.

Going back to the OEM flywheel will lessen the dip, but the issue is still present. You won't stall as often though

 

There's a setting for increasing the iacv opening when a/c engages. Can't recall the name.

 

I have read about the issues of lightweight flywheels, noises ,higher revs, etc.I have not once heard about them destroying iacvs. Almost like clockwork I will put a oem one in, the car runs perfect for 4-5 weeks and then all of the stalling, idle search, comes slowly back, like the movie groundhog day. My car does not like to eat the cheap ebay iacv valves they dont work, only oem that cost 360 a pop.

 

What frequency are you running to the valve? Maybe post the msq?

 

A flywheel can't kill an iacv. Post your tune and some logs

 

Sounds like some tune settings are killing it.
i had megasquirt installed and tuned and the only change i had to make with a light flywheel was in my left leg.

 

I drove the car for 1 year with the ms3 pro, e -85 flex fuel tune with no issues except hard cold start on e-85, No iacv issues. I was able to put down 229 whp dynojet on e-85, I was getting spark blow out at 12.9 psi. I had the 10.5 lb flywheel installed for a few weeks before the big spark kit running sequential ,36-1. The new tune put down 224.5 on a mustang dyno at 15 psi. My tuner is a well known for miata megasquirt tuning and other cars, including race cars. I was told to get rid of the flywheel. I dont have any tuning maps, I will try to get them.

 

Unrelated—

By the way, do you really mean 36-1, not 36-2? I never heard if anyone ever got the -1 to work.

DNM

 

I think it is from a oem mazda protege.

 

I had a 10 lb flywheel on a turbo track Miata and never had iacv issues. Those aren't rare flywheels so post your tune so we can look at the settings.

 

Here is some more info about my tune. When I had the ms3pro and mods installed it was first tuned on pump put down 198 whp, the tank was drained and filled with e-85 and retuned ,made 229 whp. oem flywheel,no iacv issues for 1 year. Later on I had the 10.5 flywheel installed and a few weeks later I had the big spark kit running sequential and 36-1 trigger wheel installed. we only tuned it on e-85. I always run a tank of pump gas every 4 weeks. Do you think original the pump gas tune and the new e-85 tune are not merging correctly, it this is causing my iacv issues? There is always a mix of e-85 and pump, I figured the flex fuel sensor would adjust.

 

Post your tune .msq or we can't help you much.

 

dyno and tuning logs were on my old cell that crashed, tuner not sure if he still has them. Today, changed the plugs,(old ones were still good) pcv, and a new ebay iacv installed, would not hold idle. Put the oem iacv back in and the car is running perfect again,starts up, holds idle no heavy e-85 smell.

 

Either learn how to get the tune file off your ecu and datalog the issue you're having or find a tuner who is willing to properly tune your idle.

This is not a mechanical problem. This is 100% a tune problem.

 

I plan on doing that asap.

 

When you change iacv it will need slightly different settings from the last one. The tune can be trying to close the valve when already fully closed or open it further when already fully open or operating at the wrong frequency.

Get a laptop and download TunerStudio and connect to the ECU. It will give you access to the current tune which you can save and upload here.

 

What was the plug or chip that came with my ms3pro I gave it to the tuner and never got it back, I guess it was a memory stick.

 

Thanks for the info, I am looking for a local tuner now.

 

That’s just instructions and base tune and TS software. All available online.