Fuel Cut problems at 4500-5k rpms any suggestions

[Denverr]

Hi everyone, first post to the forums. about a month ago i picked up a 94 legacy ss with 250k on the clock, engine rebuild 30k ago costing 3600. anyway. i am having an issue where when i am in boost, anywhere from 4k-5k rpms its like the car hits a wall. wont rev past and i lose all boost. Previous owner said it could be the boost control solenoid but i just switched out the 3 sensors on that passenger side strut and still no avail. it does have some mods which i will list
mbc
it had a forester top mount, but i just installed a front mount
td04
wrx downpipe
3in exhuast all the way back
full wrx interior
i have done a coffe cup mod (sadly it includes a little duct tape ((i know i know, but it seems to work)) i just installed it last night then drove 180 miles around colorado for car meets.
mushroom filter
it had a fuel cut defender hooked up, previous owner unplugged because he thought that was the issue.

I have changed the filter and plugs and the wires were changed not too long ago.

i also had to switch the ecu due to me switching my downpipe and forgetting to plug back in my 02 sensor. drove on the highway and melted some wires. Spent 4 hours cleaning the melted wires and pulling them apart, taping them only top find the ecu was fried. On this note, when i plugged in the new used ecu i could hear the fuel pump prime when i turned the car on (it was quite loud) but that is the only time i have heard it. Now when i turn the car on, it is silent. sometimes i hear a hum. I also have noticed a fuel smell sometimes, in the backseat and trunk.. it is only sometimes and i thought it was because i opened up the driver side pump cover (or whatever it is) to ground my amp ((sanded the paint off the cover holes and have 2 ground wires going to it)).

any help would be greatly appreciated seeing as i really want to feel the full power this thing has and not be limmited to shifting at 4k rpm.

I have noticed on the vacuum line diagram that there is only 2 lines going from the charcol canister or whatever it is called, but mine has 3 lines running to it. 2 seem to connect to lines that run underneath the intake manifold when the diagram only shows one running under there.

any help would be greatly appreciated!

[Denverr]

I forgot to mention, sometimes my idle rpms are at 2-3k, other times they are at what seems to be 100-200... and then other times they rest from 500-1000. I have researched a ton but have found no answers pertaining to my problem

[cj91legss]

You say you have an MBC. What do you think your boost is set at right now?

[Legacy777]

Welcome to the BBS.

You have several variables and I think it would be helpful to narrow them down. So the first thing I would recommend doing is eliminating the MBC and plumbing the line from the compressor side of the turbo directly into the wastegate solenoid actuator. This should limit boost to around 4-5 psi. If you find that you can boost throughout the entire RPM range then you were likely hitting fuel cut due to the boost being too high. If this is the case you'd need a fuel cut defender of some kind.

If you find that you still hit the RPM limit then you likely have a sensor or possibly wiring issue and you're going to need to do some more troubleshooting. Do you know how to read wiring diagrams and have a multi-meter?

Also, have you checked the ECU for any stored codes or performed the active diagnostic check? If not, I'd recommend doing both.

[Denverr]

I have not checked the ecu for codes. My mbc is turned all the way down. I can hit 9 or 10 psi. I heard factory fuel cut is at 12 for morec than 3 seconds. Fuel pump primed today so that's new. I replaced all the engine bay fuel lines and should probably replace the filter too, it looks newer but I'm not sure when. I noice if i don't go into boost i can go higher in rpms. I Am quite good at reading diagrams, but i am anovice using the multi meter. I do have one though. Do you have any thoughts on why a diagram created by a member ( don't remember who) for the vacuum lines has only 2 lines to the charcoal canister but mine has 3?

I also noticed there seems to be a taped off T running to the mbc but isn't there supposed to be a restrictor pill. I looked inside and did not see one

[Legacy777]

The diagram shows three ports on the canister, but just not the third line going to the fuel separator/tank.

http://www.surrealmirage.com/vrg3/vacuu ... vacuum.png

Each MBC is a little different so I don't know if there needs to be a restrictor pill or not. The MBC I used a while back did not have one. What brand MBC do you have?

[Denverr]

It's no named. I switched the lines and now can go to 5psi withoutgetting fuel cut till 5500 rpm. Sometimes it will cut at wot in first gear. I installed my fuel cut defender but not sure if it is doing anything. Goingback to check all my ic kines and everything. I also switxhed the coil to a diamond one i found at the junkyard. I still have yet to figure out the problem. Maybe switching the fuel pump will fix my problem hopefuly because i just want this car to run fast and well! Any other suggestions greatly appreciated

[chanley2010]

Had the same issue at 4200 rpms, turned out to be the speedo not working right, what fuel cut defender are you using?

[Denverr]

Turboxs. It came with the car. Speedo seems to be working alright. I am just at a loss. Doesn't seem like many people have had this problem and if they have , haven't posted

[chanley2010]

Are you actually in denver? I have a turbosmart defender im currrentky not using but the robtune instead. Can try it if you want

[dankberries]

I think I met you a few Sundays back at a nation wide meet, I was in my sr20 powered s13. Did you ever clean the MAF as I suggested? Have you checked for stored codes? Have swapped fuel pumps? Or checked the wiring/connectors at the fuel pump?
I would check the spark plugs and wires, plugs are cheap enough I would replace them anyway if its at 30000miles.

I've had similar problems and answered it with new plugs and wires.

[Denverr]

I think I met you a few Sundays back at a nation wide meet, I was in my sr20 powered s13. Did you ever clean the MAF as I suggested? Have you checked for stored codes? Have swapped fuel pumps? Or checked the wiring/connectors at the fuel pump?
I would check the spark plugs and wires, plugs are cheap enough I would replace them anyway if its at 30000miles.

I've had similar problems and answered it with new plugs and wires.

I have yet to clean the maf. I am not sure how to change our the fuel pump. I will need a strainer for this sti pump as it didn't come with one. I haven't checked for stored codes ( no cel) and the top connector on the fuel pump looks good. Plugs and wires have been changed within the last 500 miles. Now,uf i reset the exu shouldn't it clear the codes

[chanley2010]

My fcd was having a minor short from time to time causing a fuel cut, may have to check the power and ground to it.

[Denverr]

Cleaned maf and swapped pumps.when i do hit the fuel cut it seems to whine a little bit like electricity whine idk wherem from...

[Denverr]

I canhit the fuel cut faster if i go wot.. Seriously if anyone helps me figure out this problem ill give you 50$ over paypal... I'm so ready to be able to actually do a pull or stay on it.. Any more suggestions?

[Denverr]

Justminstalled the injectors. The old ones look aweful! Anyway.. It still is hitting fuel cut. It kind of hisses and now after installing these injectors i can hear a clicking noise over 1k rpms. I know its one of the 3 sensors but which one is it and why??

[cj91legss]

Pressure exchange solenoid is the sensor that clicks. It's the brown sensor on the group of 3 on your strut tower.

If it's clicking like you say then the sensor is probably and you might have a failed map sensor, the black one to the left of the PES with the 6 inch vacuum line looped down to it.

Another possibility is your fcd took a dump or a wire for it came disconnected.

[Denverr]

Found out its a. Injector clicking i replaced all 3 of those sensors too wtttfff

[Denverr]

It like loudy hisses when i get fuel cut like its dumping exhaust... Not a leakk
.well it might be a leak i have no idea where from though.

[Legacy777]

You should use a hand vacuum/pressure pump to check the solenoids to see if they have leaks.

[cj91legss]

You could have a boost leak post turbo too.

[Denverr]

Got around toseeing if any codes come up. Codes 31
And 23. 31 has to do with abnormal voltage to the throttle sensor. ( sets throttle sensor to fixed voltage and then 23 is airflow sensor abnormal voltage ( controls the fuel injected into the engine in relation to the throttle position sensor and engine speed. So what do i do now?

[cj91legss]

test both sensors by following the directions in the FSM which can be found on Josh's website.

If either sensor has an issue then you'll have to swap it out for a different one. When it comes to swapping out the TPS, it's much easier to swap out the whole throttle body.

You can clean the maf with crc maf cleaner and that could help.

[Denverr]

Ok so i tried to start after redoing ic piping. AND swapping injectors. I didn't pull the fuel lines when swapping injectors ( didn't know i needed to)and it sounds like banging metal when trying to start.. Like sounds like the starter is hitting something or something is hitting another piece of metal. If i try 3 times i see some smoke coming from engine bay.... I have no idea what happened... What could this be.

[Denverr]

I found that i flooded the cylinders with fuel. I removed plugs and when i pulled one of them fuel waterfalled out.. I blew out the fuel tried startong it. No luck. Car turns over but will not start at all. Any help greatly appreciated! Case of beer inckuded if you help get my car running again either over here or in person!

I did swap my plugs to my old set ( the old set only has 500 miles on them) i made sure they wernt fuel soaked. I did swap my injectors back after swapping them to the stock ones to see if that woulda fix the problem, and i noticed o. Driver side in the fuel rail it was just full of fuel it wasn't draining it was just pooling in the driver front injector housing. I have no idea!