thanks gray. Appreciate the info.

I will get some brake cleaner and try this out and report back.

just out of curiosity, in terms of nb readings. what should these be roughly at cruise and under spool and top end?

 

Narrowband will read between 0.1v and 0.9v, low voltage is lean, high voltage is rich.

 

I removed the wb sensor from the car. re-calibrated it in fresh air

then i wrapped sensor with a rag with brake cleaner on it. afr went from 21.7 down to 8.1 then remained there - waited for aboout 10 minutes then afr slowly creeped back up to 9.1.

i removed the rag, afr went back to 21.7. repeated and got exactly the same results.

this should mean that the wb gauge is in fact ok.

trying to fix my plug now to do another leak test.

 

Sensor sounds ok, where are you reading the AFR from gauge or logging software?

 

ive read from both, i normally rely on logs more however. comparing both, they seem only about 0.1-0.3 of an afr different

 

What wideband are you using?

 

sorry should have mentioned this above.

innovate lc-1 with gauge as well.

bug is welded in the downpipe - just before the flange where the cat used to be.

mods are drop in filter (cotton type but with no oil (possibly there might be a tiny bit but it doesnt feel gressy), 2.75 inch down pipe, 3 inch test pipe, hks hi power cat back, walbro, mbc 1.5bar

no recent mods.

it seemed the problem started after a batch batch of fuel although it could be just a coincidence with something else whats wrong..

 

Just one more simple thing to check, open LM programmer and make sure calibration is set to gas and not reverted to custom.

 

On cruise and idle the WB does bounce around 14.4-14.9 right? You don't happen to have a bov that is VTA do you? Maybe leaking I would tripple check the BLT.

 

wb calibration set to gas =)

i have a evo ix meal bov - pluged back to the stock rubber intake pipe.

just waiting for the other half to get home with some parts to re-make a pressure tester as i broke my other one.

i suspect it could be leaking around the injectors which i havent tested yet

 

Honestly, those are the exact symptoms of a boost leak. On light throttle (closed loop) it won't draw air in so fuel trims are normal. Then when you mash it the pressure starts bleeding out. Try this, take a log whilst keeping the car in CL say in 5th gear at part throttle but try to achieve boost, as much as you can and see if the fuel trims go way negative while boosting like 5psi.

 

update: found the problem.

after boost leak testing all the joins etc, there was no problems.

with a call around, i went to a friends workshop and put some red power type dye through the system and found there was a leak through the intercooler - but not on the front. it was on the back side (facing engine)

ive since upgraded and now everythings running great.

thanks everyone for your help. Ive learnt a lot through this exercise

 

Congrats on finding the problem! good to hear everything is well again

 

"the red power type dye" how did you apply, is it safe for the motor and where can you get this to buy?