drdl

Hi guys,

I bought a 2004 MSM a few months ago. It was running OK initially, but started acting weird. I was wondering if you guys can give me some ideas of what might be causing the problem.
I don't know the technical terms, but I'll try to describe the symptoms the best I can.

While driving:
1. The RPM will drop and the engine will stall if I let off the gas and depress the clutch.
2. If I just let off the gas and coast in gear for a few seconds before depressing the clutch, the engine does not stall.
3. If I keep the RPM up and shift the engine does not stall.

When the car is just sitting in neutral, the engine does not stall after I rev it.

The following modifications have been made to the car:
1. AEM air intake
2. Larger injectors (I think 305cc)
3. Manual boost controller (set at 9.5 psi)
4. Flyin Miata downpipe, midpipe and exhaust
5. Larger aftermarket intercooler
6. Forge bypass valve
7. Bell Engineering throttle body inlet tube
8. New clutch and aluminum flywheel

I have taken the car to a mechanic and his initial thought was a leaky bypass valve. A new one from Flyin Miata was installed and the problem is improved. Now when I let off the gas and press the clutch the RPM will dip significantly and almost, but not stall.

Now the mechanic says the issue might be the stock ECU not being able to deal with the larger injectors: too much fuel causing the stalling when I let off the gas; letting the car coast in gear allows the extra fuel to burn off so no stalling in that situation.

What do you guys think? Any ideas?

Thank you.

18psi

iTrader: (76)

sounds like he's right

Impuls

iTrader: (1)

Went to larger injectors with stock ECU? O.o
You're ECU doesn't know what to do now.

Your mechanic is right, the ECU can only compute so much and for what it's programmed for.

You may need to go back to stock injectors or look into trying to bypass that immobilizer to go standalone ECU.

18psi

iTrader: (76)

IIRC the msm guys all seem to say 305's are borderline/OK to run on stock ecu. But no cars run exactly the same, so I bet yours is one of the ones that just doesn't like it.

thenuge26

iTrader: (2)

I've never driven an MSM, but it seems that everyone who has agrees that the ECU sucks. It's probably time for a standalone, which will greatly improve the effects of the mods which are already done to it.

Either way I would turn down the boost and start reading before something goes boom. With the upgraded DP + Exhaust, you will likely see some overboost, which is probably what the PO put the 305cc injectors in there for. If the MSM ECU is like getting your leg blown off by a land mine (pretty accurate from what I've heard), putting 305cc injectors on it is the equivalent of strapping a band aid onto your fresh new stump of a leg.

Ryan_G

iTrader: (8)

Get a megasquirt. I promise you will not regret it. You will realize just how horribly the stock ecu holds back your MSM after you switch.

18psi

iTrader: (76)

True

matting the go pedal, watching the boost shoot up to 10psi, and the car literally accelerating slower than a n/a miata, then at 5k LURCHING forward like a bottleneck was un-corked made me realize how bad it is lol.

drdl

Thanks for the replies guys.

It seems everyone is agreeing with the mechanic's diagnosis. That's great.

I'll have the stock injectors put back in, and turn down the manual boost control. Hopefully that will solve the problem. If it does, I'll think about putting in larger injectors when I'm ready to go with an aftermarket ECU.

Besides the Megasquirt, what do you guys think about the other ECUs like the Hydra, Xede or a reflash of the stock ECU that BEGi offers? I probably won't be doing much more modifications to the car other then suspension.

Thanks again!

concealer404

iTrader: (3)

**** a Hydra.

Xede is outdated.

Reflash is stupid money for not much value.

Megasquirt will massage your prostate.

18psi

iTrader: (76)

MS is best for the buck, but if you're looking to stay at current levels and have OEM, well everything, then get the reflash. Its just way overpriced for what it is.

thenuge26

iTrader: (2)

I would rather pay for someone to personally tune my car locally than to send the ECU out for tuning elsewhere. I'm sure Begi does a great job, but it won't be customized to your car because you can't mail them your car. For the same price, you can get a used MS2 and 2-3 hours of dyno time.

It really depends on what you want out of the car. Do you want to learn more about it and possibly tune it yourself, saving you money down the road if you ever change anything? Or would you rather ship your ECU off, install it, and never touch anything on the car again?

Impuls

iTrader: (1)

You better start looking up a way to bypass your immobilizer, by the way, I don't remember if anyone came up with a method .

concealer404

iTrader: (3)

My car runs and drives, but i do need to take the bulb out so it stop flashing at me.

Impuls

iTrader: (1)

You remove Ecu and put standalone = not going anywhere. Unless you've already removed it?

concealer404

iTrader: (3)

My car doesn't have the stock ECU, if that's what you're asking? Hasn't had it since 2006.

thenuge26

iTrader: (2)

No ECU = no immobilizer. The immobilizer tells the ECU not to start the car. Since your standalone probably isn't set up to interface with the immobilizer, it just acts as though it isn't there.

Lee04vr

iTrader: (1)

you might have the "BOG" if try to give it some pedal and it just make noise out of the intake, But if it pulls ok it could be leaky bypass valve and just a bit to much fuel at idle/low speeds.

305's are fine on the stock MSM ECU it's really only hurting low speed and cruise fuel economy. Some MSM'S have very bad ECU's and there will be nothing you can do to get to run just right with no hesitation going into boost.
MY car responded great to a FM intake and O2 signal mod with almost no hesitation it almost pulled like it had a NA V6. However some cars had a bad hesitation going into boost and no easy mod will fix in that case you might as well just get a aftermarket ECU.

I have a HYDRA V2.5 if don't have tuning experience or the thought of a stand alone scares you don't even consider the HYDRA tuning the HYDRA is a gigantic pain in the ***.

XEDE sucks can't change the rev limiter and it's a piggy back so that little evil box called the stock ECU is still in the car.

ReFlash not worth the money and again stock ECU retained the only plus here is the car may still pass emission testing.

AEM EMS-4 is now a option for the Miata and should work fine on the MSM. I have some experience with EMS-4 helped a friend tune a Scooby the AEM software is easy to use and the EMS-4 was not hard to get tuned.

Mega squirt best bang for the buck enough said and you will have loads of support on this forum.

All of that said the HYDRA on my car days are numbered after working with the EMS-4 and the mega squirt I built for my truck, I'm tired of the HYDRA it is such a *** pain to tune compared to almost any other good ECU on the market I even wonder why FM hasn't found a better ECU to use in there cars.

Impuls

iTrader: (1)

I thought you were the OP, My bad.

The immobilizer is separate from the ECU though isn't it?
I should know. I have my 04 MSM's harness in a box but I didn't wanna use it and much easier to just use my '99 harness. I forgot though, I may be wrong it tends to happen.

concealer404

iTrader: (3)

Unfortunately, i'm "blessed" with Hydra 2.5 on my MSM as well. FM tuned it for me July 2011. I haven't really driven the car since, since it runs like total *******. I hesitate to blame FM, as i'm 90% sure it's just due to a total piece of **** product. But the fact that THE miata dealer for Hydra couldn't get the thing to run halfway correctly in a 2 hour session speaks volumes.

I'm giving it one more shot, then this **** is going away. Seriously horrible.

My immobilizer is constantly going off, i imagine it's probably bypassed, though. I was told this has something to do with why i have to use non-factory keys. (Those keys are in the glovebox, i dunno.) The light constantly flashes on the gauge cluster. I think the car just thinks it's always stolen.

Lee04vr

iTrader: (1)

I spent countless hours messing with the Hydra's tune trying to get the car to run just perfect. It runs good makes good power, but I'm going to get a EMS-4 or MS3 soon when I start my big power build.