Following on from this thread
http://bbs.scoobynet.co.uk/showthread.php?t=483253

MY2001 Jdm Sti 7.
Underload on light throttle in the higher Gears 4th & up seems to hold back / surge. If you gun it through the gears No problem. Car went to Tsl & they could not find any issues apart from the O2 sensor was a little slow on cycling.
So i replaced it >>
Now, Question ??
Why would a new O2 sensor appear to make this problem Worse ???
Any Ideas Please.
Thanks V Much
Dean

 

Bump

 

ive also got this problem on my sti 7.... really annoys me when on motorway.. do you have a VTA dump valve fitted? did you checked all the hoses under the intercooler??

let me know if you solve the problem

thanks
kevin

 

Hi Kevin.

No Vta Dumper, just the standard one, I have not had the intercooler off yet, One of the next jobs.
& i have to agree, On Long roads, Dual Carriageways & motorways it is really annoying, I Love the car but it's P1ssing me off.
I'll keep in touch.
Im planning on isolating a few items, Boost solenoid, Wastegate Etc also.
Mine does not stay constant, Some days better/worse than others !! What about yours ??
Dean

 

mine only does it when on 5th or 6th gear on motorways, when i floor it every gear its fine..??

 

Yes, Sounds exactly like mine !!!

Dean

 

 

Hi Kevin.
I never got round to the Boost solenoid test. But i did replace my battery as the voltages were low & after 2/3 days standing it was a little lethargic at starting, I also reset the Ecu.
Now since this, The car has seemed Tremendously better, I will have to keep an eye on it , but for the time being it seems Ok.

Keep in touch.
Dean

 

thanks Dean, but how to you reset the ECU in a Newage??

 

Does your car have a decat without having been mapped for it ?

If so, then 99% sure it is the boost control set up in the ECU, they need substantial work on the control loops and wastegate settings to avoid the boost surging (not compressor surge, thats different) on light loads in higher gears.
The JDM ECU's run a very nice programme (much better than the UK of the same year) so it can be mapped out.

Andy

 

thanks andy F, yes its got a full deacat....but is there another way round this?? as i am thinking to get it map when i get all the bits together.??

thanks
kevin

 

In the short term you can fit a larger boost restrictor in the T piece between the wastegate and turbo outlet. This may also reduce your full boost level which is probably not what you want !

Andy

 

Hi Andy.
Mine still has the Cat in the downPipe !!??

I see your down with Graham (911) in March, Im seriously thinking Remap, Remap & Remap Can you Pm me a rough cost Etc.
Thanks

Dean

 

Dean, i have had my car fixed now, i have updated the thread you referenced, but for your info this is what i put,

Hi, my car has been fixed. It was fixed by Richard Bulmer (the original mapper)and Pete at Prosport in Stockport. I dont think it was the map as such, but the fix did involve a software change, something to do with the Lamba controller, whatever that is????? Anyway Pete is confident that they have now found the fix to this issue, give him a ring.

steve

 

My car does this too. I am saving up for a remap to have it sorted out but also have a fuel pump and an exhaust to fit before I can get it done.
I currently have a full 3" decat and am changing to 2.5" for driveability and noise reduction purposes.

A question though, if I fit the standard exhaust will the problem go away ?

Cheers

Ken

 

Cheers Steve

The lambda controller issue would probably fit with me replacing the lambda & the problem feeling worse !!!!
I'll give him a call

Dean

 

What is a Lamba controller then?

Ste

 

I think this is just a section of the Ecu programming which interprets the signals from the lambda sensor & makes the fueling adjustments Etc..
Or i could be way off the mark & talking out of My ButtHole

Dean

 

The Lambda doesn't have anything to do with it.
When underload on any positive boost the ECU does not refer to the Lambda sensor as it runs 'open loop' or at least thats how it should be mapped to operate, if not then the Lambda switching maps were wrong in the first place.
I suspect your boost parameters may have been corrected
I hope they didn't charge you for it !

Andy