I own a S5 TII with minor mods.Intake,bov,fcd,mbc & a custom exhaust setup.Whenever I open up the mbc about 3 full turns and go to drive it the car hesitates,bogs,jerks & makes popping sounds out of the exhaust b4 I can even hit boost.I have to drive slow, if I press the gas to hard it does that bs and can't even accelerate unless I basicly feather the gas pedal.Then when I close the mbc all the way I can go to WOT or drive fast without any problem.Any guess's as to what could be wrong here?

 

Do you have an aftermarket boost gauge?
Do you know how much boost you're running?

http://fc3spro.com/TECH/FAQ/fuelcut.html


-Ted

 

Yes

About 5psi with it shut all the way

 

my S5 TII did the same thing... I have no idea what caused it... I'm currently installing an aftermaket ECU to try to get rid of it haha.

I'll be interested if you find out how to fix it

 

Yeah this sucks man wish me luck

Let me know if that aftermarket ECU helps any.

 

man thats a fucked up problem
sounds like something wastegate related to me...
have you checked vac lines or anything stupid like that?
have you tried turning your mbc all the way down then up a couple notches and testing (driving and checking boost)....then up a couple more and testing(driving and checking boost), and so on? perhaps three full turns is too much for the stock turbo?

 

Yes ive checked all vacume lines & hoses there are no leaks what so ever.Thanks for your input.I'll try opening it a little bit each time instead of making full turns, perhaps it's open to much causing the FCD to act like that?

 

Quick-n-dirty test...

Unplug the electrical connector from the boost sensor.
Go take the car out for a drive...
Does it do the same thing???
If the car stops doing the hesitation, it's definitely the overboost fuel-cut.


-Ted

 

but he has a fuel cut controller....

 

Do you mean pressure sensor?

If not where is the boost sensor located?

 

same thing. on the passenger side strut tower

 

after reading it a first time and him not having a boost guage i've been guessing he may be leaning out and running way more boost then he should....

a boost guage helps wonders, i would never drive another boosted car without one.... along side an AF guage....

 

I have a aftermarket boost guage lol...

please read better & look at who/what I quote.

 

Now it even does that even with the mbc closed all the way wtf.

 

doesl the car barely run when it's like this? is it a bitch to start sometimes?

this problem happened to me when I blew one of the lines off of my BOV pipe. the exact same symptoms that your having right now. i practiacally have the same mods you do. check/look hard for leaks around the turbo and bov section (especially all of the nipples). seems to me like it could be a leak in one of the lines. it's the fact that it dies near boost or hard acceleration that leads me to this, b/c thats what happened to me.

think you would know if you detonated your motor. you're post would be much different

 

The car runs fine until I floor it or push on the gas to hard.Sometimes I have to crank it alot to get it started but not to often.I checked all the lines around the bov and they are fine.The car never dies it just pops and has huge hesitation when going into WOT or if I put to much pressure on the gas.It jerks me and the car around until I release pressure from the gas pedal.I have to drive like a granny basicly.Ohh and it never does this on a cold startm, it has to be driven and warmed up for awhile b4 it has these symtoms.

Im frustrated.Im about to just take it to a damn mechanic even though I don't really want to....this sucks. My bro had a similar problem with his eclipse but it wasn't as bad as mine.He took it in and they said it was the transmission speed sensor, anyone think that is the problem here?Or could it be a bad o2 sensor maybe.

 

we dont have a speed sensor for the tranny, just the cable.
hhmm... is your car throwing any codes? if it bucks and sputters under hard accell, the only other thing I can think of is the water temp and air intake temp sensors.
this sucks man, sorry to hear about this.

 

Wish I could offer more help, but I'm not sure. Maybe the injectors have an issue? If you can get a hold of a wideband O2 sensor, hook it up to the Air/Fuel Meter (or just datalog it) and see what happens when it stutters.

I had a black '90 with a Haltech with the Haltech adjuster ****, and if I turned it to -12.5% fuel at idle it would really stutter, and if I turned it to +12.5% fuel at idle it would stutter too, so it could be either going pig rich or really lean, might be an injector problem, I dunno, if it's not a vacuum problem.

 

might be water temp sensor. I had similiar problem with the stock ecu. I never knew what it was though. Prolly something with the spark plugs/wires. I installed the Microtech and it went away.

 

Could not changing the plugs and wires eventualy cause this problem?My car hasn't had a tune up ever since i bought the car which was like 2-3 years ago and I drive it alot.

 

yea change the plugs and wires. Start with the plugs first. If its not the plugs I will paypal you the money for them. Im pretty positive thats what it is.

 

You should do as MARTIN said and a full tune up. That is allways in order. Check specs of your TPS and Water Thermo sensor as they cause drivability issues.

After this if problem persists I say bad ECU.

EDIT: I have had a similar issue. I blew a clamp / inter cooler pipe on my FMIC. Under heavy loads or when it would build boost it would push the pipe out creating a leak. This makes the car react like you say. When I let off gas the pipe would slide back into place. The reson it would only do this when warm is the ruber hose would become weak and stretch when hot, causing the clamp to become weak.