Hello there,

I have had a nightmare of a troubleshooting on my boost cut. It happens when I start to get into boost and at about 3-4k rpms and around 6 lbs of boost it hits a wall and will not go further. I have been lurking the forum to fix the issue for about a month and a half and I am finally getting impatient.

What I have done:

1) Wired turbo control actuator open.
2) Wired Charge control valve open.
3) Removed UIM and redid all the vacuum system for a non-sequential.
4) Adjusted TPS.
5) Replaced leaky blowoff valve.
6) Tightened wastegate arms

What I have noticed..:

1) I can unplug the ECU and it will stop for a short time but eventually the cut will come back and I cry.
2) I have tried 3 ECU's and it has the same symptoms on all of them.. So I assume its a sensor issue.
3) If I keep the boost below like 5 psi, I can rev to redline.
4) There is a slight 3k hesitation but all the grounds look fine to me.
5) Slight amount of bucking under 2k rpms when off the throttle.. But the tps is in spec.
6) When it cuts there is a very large backfire.

I really want to figure this out.. I hate not knowing if I am going to boost or just backfire like crazy...

Thanks in advance!

 

Bump!

I dont want my fresh rebuild to go in vein!

 

gave you checked ignition and fuel systems?

 

Well the thing that confuses me is the fact that it runs 100% perfect when it is not boost cutting.. So I'm thinking sensor error.. but I am not sure. Any thread that has anything to do with this is always incomplete or slightly different.

 

have you checked the boost sensor? if you have a spare replace it...

EDIT

And check the line that goes to and from it, make sure it isn't plugged.

are you using a stock boost sensor?

 

Have you checked for codes?

Sounds like you have a bad OMP

 

No codes other than emissions stuff from delete. Its not in limp mode. It goes to 7k out of boost fine. I am going to try to swap out the stock boost sensor for another stock one and see if it solves the issue. I'm thinking something is sending a weird signal saying its overboosting. My best guess is the map sensor.

 

Do you have HKS Twinpower installed?

 

That's my guess, the sensor might be fine under vac....

 

Well the little filter thing on the vacuum line was backwards.. So I turned that around and went over all the grounds and it seems to be doing fine... Ill update if it does it again.

 

what filter thing.... I didn't think the boost sensor had one?? Either way glad to hear it is going again.

 

The piece is in my diagram between the manifold and the map sensor..

But.. Update. The boost cut came back. I'm fresh out of ideas. Ill try a new map sensor tomorrow. I do believe it is in fact an ignition cut.. So I am not sure if that will help.

No hks twinpower installed.

 

let us know how the changing the boost sensor goes... what page is that on btw, I can't seem to find it on my parts diagram...

 

I have to find a boost sensor. Maybe the power fc I'm getting will tell me more.

And the filter. Its on a vacuum diagram.. not sure on a page number as I have a digital copy of it. It basically keeps oil and grime out of the map sensor. I would suggest getting one if you dont have one as it is sure to help prolong the life of your boost sensor.. But who knows. Maybe mine is clogged

 

lol... yea who knows. thinking about it, I probably should...

 

You can do all that modification on stock ecu?

 

Sounds like the car is in limp mode

 

I have the power fc. And no boost creep issues. I can maintain a solid 9 lbs.

The car is not in limp mode.

 

That's strange... Do you know what your fuel pressure is at @idle?

If you can, post a picture of the power fc voltages for the sensors, with the car idling

 

Ill post pictures of volatages when I get it tomorrow. The fuel pressure was checked by my shop and it showed it was fine (rotary shop).

 

Also I might add. I believe it is an ignition cut. Maybe that will help diagnosis. Ill continue my search.. I just want to make sure I have it all running 100% before I start working on body goods.

 

did you change out the boost sensor?

 

Yeah swapping the boost sensor did nothing. BUT A CLUE!! I got an intermittent check engine light and pulled the codes. I got 11- intake air thermosensor. It can cause poor gas mileage. Check! Strange idle/ bucking deceleration. Check! Possible boost/ spark cut. Check?

I might be getting excited for nothing.. But I ordered one from my good friend Marc at FD3S Engineering last night and it should be here soon. I'm curious to see what the IAT is reading right now. I should have the Power FC soon. A little address confusion got it shipped wrong.. but its on the path to my home right now.

 

I've been following your thread and just wondering if the intake air thermosensor fixed your problem. Can you give us an update? Thanks.

 

I think the power fc solved his problem.