V5-6 classic o2 sensor // jdm hunting issue
 

Having a little running issue with v5 classic jdm sti
dose anyone have a good o2 / lamda sensor, I can
buy or borrow….

basicly the idle is poor when up to temp and it’s hunting,

cold start it’s fine but when at full op temp it’s hunting
ive done a smoke test without joy so gonna start changing
a few sensors, I’ve done the icv already still the issue continues
so now gonna try the o2.

I would buy new from icp but just want to see what about first

pic is of what is currently fitted


thanks CSF


https://cimg2.ibsrv.net/gimg/www.sco...e4ec364a8.jpeg

Usually a symptom of a bad MAF on v5 and 6 cars. Any codes.

No codes

ive 2 mafs here so unless there both bad
I know the v5-6 mafs are fragile so maybe the cause
One step at a time I guess

Those MAF's are near a service item on v5/6. Half the time never throw a code.

i had no codes on mine , i cleaned the maf , i only had carb cleaner so not ideal , the issue resolved for a short while so i knew it was the maf , new one bought issue solved , i would expect an 02 issue to throw up a cel , fuel pump or coolant temp sensor cam or crank sensors ?

Hi peeps, ok I’ve just ordered a new genuine maf, I’m really hoping it sorts the issue
My only concerns are there are no issues from cold surly if it was a maf the issue would
be there cold & up to temp, either way as your saying they are fragile so it good to rule it out
if that not the issue I guess I will hunt for another o2 sensor and see what happens but hoping the new
maf sorts it

make sure you flatten the ECU every time you try something new or it may leads you on a bum steer........

easiest to test the Lambda on that age is simply unplug and if its 100% improved then there is your issue

yeh I figured that out with the new icv
I didn’t reset the ecu and it ran like a bag of
nails with the new one,,, reset it and was
fine…

with regards to the lambda, can I run the car up to temp
so the hunting starts, shut it off discon the lamda and see how it behaves once restarted
with it disconnected, I’m just wondering what I should be looking for in terms
of behaviour I mean if it is the lambda and I unplug it when up to temp what should
happen.

as said before there are no error codes / lights on the dash

@Vxr2010 @stockcar
did you discon the maf whilst running did it make any difference ?

when I get the car up to temp and discon the maf it cuts out
at the moment I thought that meant the maf was ok or can it still
be faulty the new maf should be here tomorow so ….

Ive also Discon the lambda just now when the issue is happening and made no
differnce to the running of the car…

Any other suggestions to try that could be causing the issue…

again once you to full temp it’s hunting usually 6 times up down then catches and idles
fine until you hit the accelerator and come off then it dose the same again 6 times ish catches and so on

disconnect the Lamba and then drive the car as you normally would and see if it helps........

when i disconnected the maf when running it would cut out , i was getting more power less power , bad running , stalling , rough idle , changed the maf all sorted , clean the throttle body , and no eml’s

i had running issues on my 04 Fsti , i disconnected the battery plumped the brake pedal 50 times , reconnected and it was fine , one was just the mrs using the throttle to start the car which is not good , the other was a boost issue a leak and boost solenoid playing up , did all the bits to sort it no charge , did the above and it is not a proper reset but possibly resets fuel trims ? and helped , if it’s doing it when up to temp could also be coolant temp sensor , when you start fuel is rich , when it’s warmed up it’s supplied to lean out , if the temp sensor is not working it’s not leaning out

@stockcar
We might have a winner, ok so i Discon the lambda took it for a short drive off boost
bare in mind the car was already pretty warmed up from the same route I took earlier
But this time no idle issue at all whilst driving with the lambda disconnected would the prognosis be that the lambda is shot to peices
?

thanks for you help alyn…. Very much appreciated

The lambda and MAF talk to each other via the ecu all the time. One says x amount of air going in and then the lambda says too much or too little fuel so the ecu compensates with the fuelling. The lambda only works at idle or cruise the rest of the time it is basically inactive. The right thing to do is put a scope on the signal wire from the lambda which is black the two white wires are only for the heater. The signal should fluctuate between 0.1v and 0.9v. When you disconnect everything the ecu resorts back to a default and could possibly be called limp home. Fuel economy will be terrible and engine efficiency will be terrible. Both of the said sensors only generally throw a fault if the heater circuit is knackered.