This happens only when there is no load on the engine. If I'm at a stand still and I blip the throttle the car (05evo8) sounds like it's hunting for the idol rpms but it dips down to 200 rpm then raises to 2000 back and forth and stals out on most occasions. Even when I'm driving and getting on it there no problems until I throw it in neutral like I'm coming to a red light it will to the same thing and try to stall out..I have to constantly blip the throttle to keep in running...no vacuum leaks, good spark, new plugs no cels..this is literally killing me....

 

When did it start happening? mods list? did you check the intake air valve on the TB? can you log the issue?.....
You can adjust your BISS screw for now to save it from dying but you will notice higher idle speeds.

 

Had a cel took it to a tuner, replaced exhaust mani they retuned it started having the issue after that..had a falling out with that tuner..took it to another tune shop said they did everything possible in the ecu must be something mechanical and still happening..new TB has 272 264 cams has 7460r turbo 900cc fic injectors as fuel rail walbro 250 pump no mods added after the issue started replace bov, no change in issue

 

Log rpm, tps, iacv, ign timing, inj pw, afr, then post it up.

We should be able to see the pattern from that data.

 

Have you done a boost leak test (will also find vacuum leaks)? Mechanical stuff to look into would be the ISCV, Fuel injectors ( may need cleaning). Ignition coils and plugs, and the fuel pump, EGR Valve (stuck open maybe). This is of course assuming something isn't screwed up in your tune. Do you know what ROM you are using? Once you do you can compare it to an off the shelf version and look for any weird stuff in the idle stability related tables.

 

Boost leak test result or else! :}

 

Unplug and replug in the IAC valve. Sometimes the plug comes a little loose. It's a black plug under the throttle body.

 

Yea did a smoke test no leaks only one was from the throttle body shaft seals. Ended up putting a new oem throttle body. Tested the coil packs fireING fine I will have to do a data log tmw

 

I'm having similar situation but mine gave me the check engine light for the tps, so I changed it, no chk eng light.....now car wants to die then rpm rises...

Is there a Calibration period after we change the TPS? I didn't get to drive it yet.....

going to mess with IAC......

 

best thing to do is log how many steps are required to maintain a stable idle with the engine warm, then adjust the biss untill your log matches the number you have set in your rom. The other way to do it is to use the actuators section of evoscan and activate the "Speed Adj. screw mode" setting. Then adjust the biss until your idle matches the idle you have set in your rom. If you can't make either of these work, then you either need to clean your throttle body and check for vacuum leaks ore your IACV needs to be replaced.

 

If you pulled the battery it will have to relearn, this can take some time. If its still doing it in a week you should probably start investigating.

 

yes, thats what I was thinking

thanks

 

@Idol @stalling
Rpm. 1100 200-1500. Sometimes shoots to 2500 holds and comes back down to idol or goes from 2500 to 2000 back to 2500 repeatively.

Spark adv.18-21 @idol___36 @stalling 5 when it's trying to recover from stalling

Injector 1.5 @idol____3.8 @stalling

Vaf 4.3 grams 31-38 hz @idol
14.7 grams 106 hz @stalling

Maf 10.9-12 @idol___7.9-23 @stalling

Short term fuel trim 0-6.3 jumps around @idol____0-negative 17@stalling

Once again new throttle body new plugs coil packs have good spark no boost or vacume leaks only tries to stall in neutral moving or not moving

 

@Idol @stalling
Rpm. 1100 200-1500. Sometimes shoots to 2500 holds and comes back down to idol or goes from 2500 to 2000 back to 2500 repeatively.

Spark adv.18-21 @idol___36 @stalling 5 when it's trying to recover from stalling

Injector 1.5 @idol____3.8 @stalling

Vaf 4.3 grams 31-38 hz @idol
14.7 grams 106 hz @stalling

Maf 10.9-12 @idol___7.9-23 @stalling

Short term fuel trim 0-6.3 jumps around @idol____0-negative 17@stalling

Once again new throttle body new plugs coil packs have good spark no boost or vacume leaks only tries to stall in neutral moving or not moving

 

This is how it works, when the throttle is closed, the only way for the motor to stay alive is by actuating the IAC via ECU to provide the necessary amount of air to allow for the engine to idle at a set rpm. So for every rpm target (900, 1000, 1100 rpm) the IAC should correspond to the correct needed amount of “steps” or openings you can say to allow the motor to “breathe”

When the rpm oscillates or hunts, the ecu will run a PID control (I think its PID type in mitsu) to correct the oscillation. Depending how aggressive or “lazy” the PID was tuned, you may feel a delayed response or aggressive swings like you are describing…. Jumping to 2k…etc

If we think the tuning is all correct, then the other thing that could throw things off is the BISS adjustments or a leak which u ruled out. You mentioned that you put on a new throttle body, its possible that the BISS on the new TB needs some adjustments. If you are familiar with what I am describing and can adjust it in your garage while this oscillation behavior is occurring, then you could resolve the issue.

IAC typically will relearn its locations (Park..etc) especially after a battery disconnect, when the key is turned on but while the engine is off. I think it takes a 2 secs or so to complete this learning. Someone could confirm.

Do you have access to another IAC valve that you could test?
GL!

Ps. Biggie is on the same track....