When I'm driving then I disengage the clutch my rpm's drop really really low then they raise a couple hundred rpm then they drop really really low again. Sometimes the car just dies. My mods are in my signature.

 

Yup you got an issue

 

I had that problem since the first day I purchased my car.

Let me guess, sometimes the idle will get so low that power steering and power begin to become manual- in others you end up having to use more man power to get a desired result. On some other days, however, I was not so lucky. Sometimes, while going into a turn, or slowing down, if I engine braked, and then disengaged the clutch, the idle, and the engine, will completely shut down. No Codes, and starts right back up.

I complained the first year of my ownership to Mitsu, and honestly, unless your car is completely stock, it’s useless to worry about it. Although, I must say that I did have a battery go bad on me, and ever since the dealer warrantied my old battery, my car has yet to completely shut off, however, it will occasionally get into the 400-500 rpm range for about one second (my 97 Supra TT idles at an ultra low 400-600 rpms on the stock cams)

Electrical is difficult to diagnose well without having a lot of background experience. If there is anything I can't predict, it's electrical. A low idle doesn't necessarily mean something is wrong with the car - the car could have been designed to do that either for emissions control, or to reduce wear and tear, we don't know.

Something I should note is that since the day I purchased the car new, there has always been a constant reminder that the electrical system might be the sore point of my car; it will occasionally have hiccup. Honestly though, I am so used to driving highly modified vehicles, that what I am experiencing with my EVO is nothing. If it threw a code each time this happened, that would be a different story.

Keep me posted. I am interested to see how this turns out for you.

 

Bov?

this happens in 2 of my friends cars cause they both put on BOVs on their cars...exactly what your are seeing.

 

I have a Evo 9 DV...just thought I'd throw that out there. I just took it out and it was fine. I might just have had to let the car warm up or something. I'll keep you informed thought.

 

To the OP, Shiftt IX MR has described exactly what happened with my Evo as well. All after the cam install, might I add. It did this only with the A/C on. If I approach a corner or turn, and prepare to downshift, the RPMs will drop to the point where it turns off or hits the 400-500 RPM range and bounces up again, to prevent the stall. After I had my cams installed and "dyno-tuned" by the same company, I had the car turn off on me while cruising in third gear, in traffic, along with multiple stalls just coming to a stop sign, with no turns or downshifts. Mind you, the car was supposed to be tuned and I had all those problems. Chris from Mellon Tuning has done an outstanding job repairing what possible damage could have resulted from the previous tune (poor idle quality, poor timing, high knock counts, etc). Since Chris has taken over (approx. 6 weeks ago), it has only stalled once and I think that was due in part to the car being cold (not fully warmed up), along with the knock count being reduced drastically. After the "dyno-tune", my Evo ran horrible and I was disappointed to the max. Now it feels like a totally different car (and we still aren't done yet ).

 

Sounds like BOV or boost/vacuum leak. Did you but on a new BOV?

 

This occured on my EVO from the moment it came off the dealer's lot - with six miles on the odometer. I'm not at all suggesting it is not what your saying it is, rather, I think if anything it could be my BOV.

Any type of symptoms you could decribe from having a faulty MR BOV? It will vent in small rapid bursts at low RPMs, whereas at higher RPMs it's a single large vent.
I am not sure if this is considered BOV "flutter" and am comparing it to my Supra which has a aftermarket HKS unit.

You got me thinking now......

p.s. Call me lazy, I just don't have the drive to chase down the information I would need to be more literate with the my vehicle and modding it. School and work just leave me with nothing else at the end of the day. Sorry I work better with my mind than my hands. That's why my EVO has remained basically stock. I figure the less I touch, the less that can go wrong.

 

mine does this, ONLY with the AC on...the rpm needle drops suddenly, and if it doesnt fall all the way down to 0 and shut off, it will sometimes drop to 1-200 and bounce back up. I've read it is fairly common with cammed evos. probably the only way to fix this is to get it retuned to ac friendly

 

That's it!!!!

Let's all go A/C-less!!!

Problem solved, let's go home.

So to be more specific, the low rpm/engine shut down seems to occur during decel, regardless. Could this be an electrical problem whereas the drivetrain -during decel- shrinks the electrical to the ECU? This would explain why no codes are thrown, and why it will start right back up as if the car were manually shut off with the key.

If you removed your key during a decel, or turn in, would the overall results differ much from what we are experiencing? Last I checked, the results are the same.

My logic behind this is that the EVO undoubtably absorbs energy during decel, the amount of enertia, and centrifical drag is enormous. Before this intially occured, I always had this "feeling" that during disengagements of the clutch, the engine would just/ be prone to shut off. As if the clutch disengagement is the trigger by reducing the amount of current created by the alt. However, what the hell would your battery be used for?

What is the standing charge of your battery disconnected from the car? Maybe the batteries just aren't charged well enough to provide consistant bursts of energy to compesate for what is absorbed through the drivetrain. That would seem to support my statement that my new battery "seems" to have solved my shutting down problem.

 

mine does a similar thing, but hasnt happened recently. seems like just what you are describing. after i have been under very little throttle and disengage the clutch, if you just wait for the rpms to fall down to idle sometimes they will fall below the usual and almost stall like you said. i think its BOV related, as i have the MR too.

 

how can a BOV cause an engine to die during turn-ins and decel? Why does this not occur all the time?

 

i have never noticed this... i also have a IX bov. i avoid using AC too because it acts weird when it's on, but every evo does. doesn't do this though.

 

of course it does becasue its obviously drawing more power away from the motor...and thats why when you turn off the ac the car acts a little more stable...if your battery is not brand new or at an absolute full charge your going to see problems with idle...and especially evos with sound systems at all drawing more current than stock...my evo does the exact same thing and doesnt do it with the ac off and the rest of the power available to the motor...this would also indicate that my batter (red top optima) isnt handleing it very well, as I do have 1400 watts of JL and Alpine equiptment running off that same battery...however my car is at 330 awhp so I run much bigger ground wires to help the electrical system "breathe"so to speak...just my evo, my experiences, hope something helps i hate it when my car dies

 

vacuum leak for sure