ok, so here's the story,

Day 1 - i get into my car to go for a drive on the highway, after about 20 mins of 'spirited' driving i press to accelerate, when the rpm reached 4400 i got a little stutter for like a half second and the rpms kept going. so i slowed down wondering what that was, accelerated again and got the stutter at the same rpm again, so i keep below 4000 rpm for the rest of the ride home

Day 2 - while driving and boost reaches about .5 bar i shift from 1st to 2nd, when i came off the clutch and pressed the gas the rpms drop straight down to 200 followed by several loud misfires and then the rpm picked back up. it happened a few times again for the rest of the drive.

problem has me kind of worried now, i figure well i will go to work with the car tomorrow as its friday and investigate the problem on saturday (work is like 4 mins from home, what can go wrong in a 4 mins drive right)

Day 3 - went to work, only got onle little pop when i nearly reached, so i say ok, just drive nice and slow. when leaving work, traffic diversions result in longer (20 mins) drive home, that is when hell breaks loose on the car. severe misfires if i try to pull of, it's like one there is engine load it misfires. i manage to creep home, but it get so bad the car cannot even idle and it cuts off about 20meters from home
i just push it the rest of the way

now it had all the signs of bad coilpacks, so i ordered a set of SparkTech non CDI, when i got it i installed it and problem is still there, so i began checking other things
checked all hoses to make sure they were attached and tight
checked if all sensors were plugged in
checked the spark plug gaps
changed the plugs, still had same problem
checked the tps
checked the maf (tried one from another evo)
cleaned and flushed out the gas tank

thats what i can remember i tried.

here is what i have not tried, checking injectors, checking the ecu, compression test, and boost leak test. now when the car starts it idles normal for about 30 seconds before the problem occurs and it has the same intake pressure it always had, which makes me wanna rule out boost leak

now some info on the car. about 5 months ago the engine was rebuilt and a OEM gasket overhaul kit was used, so all gaskets and seals good, here are the specs on the car

EVO IV GSR

Forged Wiseco Pistons
Eagle Connecting Rods
ARP headstuds and bolts
New Standard Crank with New Bearings.
Full Gasket Rebuild kit New
All engine seals New
All Belts New
Megan Racing Manifold
TD05HRA-16G6-10.5T Turbo
Shaved head From Japan
AMS Balance shaft kit
Tomei 260 Cams
Grounding Kit
HKS RS full Piping kit
HKS Mushroom filter
RS Quick Steering Rack
RS Close Ratio Gearbox with Razzo Short Shifter
Lightened Flywheel
BREMBO Brakes Front and Rear
CUSCO Hardcore LSD Diffs Front and Rear
CUSCO Strut Braces Front, Rear, and Lower H Brace
OHLINS Coilovers (Fully Adjustable)
HKS Braces Inside Front Fenders
Turbo timer
Digital Boost Controller

that about covers everything the car has


i know is a big post to read, but i need some help as to what this problem is!!

here is a link to a video of how the rpm moves (the bang in the middle of the video is the pop i get when driving)
http://www.youtube.com/watch?v=Dbms5gme7Yg

normally the rpm jumps up to 1500, but i was trying it for a while when i made the video

 

when it drops to 200 rpm if your bov is venting that is the problem i have the same problem with venting but i dont let that bother me =). the rest of it idk i had an idle and cold start issue and it was a bad idle air control valve start your engine and unplug it if it makes a differnce then thats not your prolem if it runs the same its possible it is bad if it is not that it could also be your maf try unplugging that while its running

 

Dayum. (-_-) I know what your problem is.

You forgot to feed the gerbils running your engine. Tsk Tsk Tsk.

Poor buggers probably in Heaven right now.

LOL, in all seriousness though. I wouldn't know. Hope you get it fixed though. =(

 

I'm no pro but maybe your IAC valve?

Just throwin it out there, good luck with the fix and let us know once you figure it out!

 

well i have the HKS recirculating BOV (forgot to mention it). and what could the BOV be venting at 200 RPM? i tried unplugging the MAF after i start, runs a little longer but same problem, even tried a MAF from another evo 4

 

how can i test the IAC?

pulled out the TB to check the TPS (which is relatively new apparently), but the IAC looked like the original one which is 10+ years

 

I have the same problem but the car does'nt die out. After drivng for about and hour or so it just start bogging as if a pipe went loose and cannot rev high. Hope u get it fix. I will be watching your thread. Gl

 

I had some RPM problems a while ago and it turned out to be the IAC.

Since yours is the original, I would say it DEFINITELY needs cleaned but probably best to just replace it.

 

now when i turn on the ignition i hear it moving, so i assumed it was good. i will clean it in the morning, if that turn out to be the problem, i will order a new one

gsr0801, would like to hear some more details on your problem, sounds interestion. pm me some info plz

 

Same problem for the most part have HKS also i found a couple boost leaks.....

 

ok so when i said it would drop rpms from it venting i mean when you rev it up and if your venting it will drop to 200 rpm but after i ceen your video i see what you are talking about. when things like that started happening to me i replaced the idle air controle (IAC). if the guy in parts over at the dealer likes you leave him the money and ask him to let you try it out and they arent supposed to let you but they let me and dont pay what they ask for it its like 450 they ask ask them for dealr price they will usually give it to you and good luck

 

well i took out the IAC today and checked it, possibly one of the cleanest parts in my car!

when the ignition is switched on, what type of noise is the IAC supposed to make? before it used to make a whirring noise for a second, but now i hear a few clicks

oh, also checked the Ohmage, 1-2, 2-3, 5-6 were all 32, 4-5 was 32.5

 

Some sort of leak you think? And where in Trinidad are you?

 

i currently have the stock ecu in, which i was running temporarily for the engine break in (had zero problems using it), so now i am going to try my power fc and see if the problem goes away. would have been running it sooner, but i was waiting for a certain person to do the tuning for me


no leakes, checked all connections, maybe some slight ones, but nothing to affect the engine.

and i am from central, couva area, pt lisas to be more exact

 

on the idle air controle their are little plastic fins on it if its the original and they breaf off and when i was trying to figure out my idle problem i thought mine was good then took a second lookk at it and they were gone if you get a new one their redesigned they are much better just ask the dealer if you can try it they may let you