02 sensor reads silly????

[AGRO]

Hi all, i recently changed my engine engine setup from cam/heads to forced induction (stock cam) ever since then, the bank 1 o2 reads fine, switches ok and so on, but bank 2 justs flatlines on around 100-180 mv on idle, wich is ridiculously increasing fuel causing a rough idle and surging on cruise, i have replaced the 02 sensors, no difference, i swaped the 02 plugs around, left to right, right to left, no difference apart from the problem switching to bank 1, i even plumbed the bank 2 02 into the bank 1 exhaust stream and still no difference!!!! :x :x :x

When at wot both 02's read fine no dramas, when idling and i reset the fuel trims, after about 10 seconds they start correcting evenly, then out of nowhere bank two reads the complete opposite to bank 1, eg: bank one reads 8% ltft, bank two reads -8% most of the time it reads -25%.

I was not sure if it was a tune issue, so i dumped a completely stock dskw os 12225074 no difference.

Please help, this is extremely upsetting. :cry: :cry:

Agro.

[Delco]

If it reads properly when cruising then it is not a O2 or wiring issue.

The O2 in this case will just tell you whats going on, what type of forced induction do you have , it couldbe biasing the air to one bank making mixtures side to side uneven , hence your issue , you also may have a air leak on that bank as well.

It may be you just have a idle tune issue , putting a stock cal will be no go on a blown combo as the dynamics are all wrong , change your fueling/spark at idle and see what happens , poor spark burn will also cuase the issues you describe

[joecar]

Assuming your O2 sensors (and wiring) are good...
Bank 2 flat at 100-180mv: bank 2 is pegged lean.
Bank 2 LTFT -25%: bank 2 is very rich.
Bank 2 LTFT -8%: bank 2 is rich.
Bank 1 LTFT +8%: bank 1 is lean.

Possibilites (a, b suggested by Delco):
a. air leak at intake manifold;
b. exhaust leak upstream of O2S (causes O2S to read lean);
heat may cause exhaust expansion which may either stop leak or worsen leak (less heat at idle, more heat otherwise).
c. one or more leaky injectors (do not shut off spray, dribbling, LTFT goes negative by alot, worse at idle);

Bank 2 is inconsistent...
Pull plugs on Bank 2 and see if they're wet.
Monitor misfire counts (misfires = wet plugs).

[Bruce Melton]

I can say they are quite fragile. Mine were reading inconsistantly due to my winding up the wires installing and uninstalling. Replaced them and all is good.

[AGRO]

If it reads properly when cruising then it is not a O2 or wiring issue.

The O2 in this case will just tell you whats going on, what type of forced induction do you have , it couldbe biasing the air to one bank making mixtures side to side uneven , hence your issue , you also may have a air leak on that bank as well.

It may be you just have a idle tune issue , putting a stock cal will be no go on a blown combo as the dynamics are all wrong , change your fueling/spark at idle and see what happens , poor spark burn will also cuase the issues you describe

It doesnt read properly when cruising, only for the first 10 seconds it reads fine, then it goes eccentric, keep in mind that i put both 02 sensors into the same exhaust stream, it made no difference, it still read eccentric no matter if it was idling or cruising, so that eliminates the possibility of an air leak or leaky injector.

Had it in open loop today, i got the afr very close to 14.7 (idle and cruising), switched the 02's back on, and yet again the trims went stupid .

it makes me think that there may be a wiring issue, am i on the right track?



fyi it is turbocharged

[AGRO]

Assuming your O2 sensors (and wiring) are good...
Bank 2 flat at 100-180mv: bank 2 is pegged lean.
Bank 2 LTFT -25%: bank 2 is very rich.
Bank 2 LTFT -8%: bank 2 is rich.
Bank 1 LTFT +8%: bank 1 is lean.

Possibilites (a, b suggested by Delco):
a. air leak at intake manifold;
b. exhaust leak upstream of O2S (causes O2S to read lean);
heat may cause exhaust expansion which may either stop leak or worsen leak (less heat at idle, more heat otherwise).
c. one or more leaky injectors (do not shut off spray, dribbling, LTFT goes negative by alot, worse at idle);

Bank 2 is inconsistent...
Pull plugs on Bank 2 and see if they're wet.
Monitor misfire counts (misfires = wet plugs).

thanks for your input joecar,

by putting both 02's (brand new) into the same gas stream, wouldnt that eliminate all the above possibilities?

[joecar]

...by putting both 02's (brand new) into the same gas stream, wouldnt that eliminate all the above possibilities?

No, it's showing that the problem is not the O2S itself.

Both new O2S's fail on Bank 2.
Bank 1 O2S reads correctly (switches).
Bank 2 O2S reads incorrectly (100-180mV, should cause LTFT to go postive...).
Bank 2 LTFT is negative.

Are any plugs on bank2 wet...?
Is O2S on Bank 2 wet...?

Must look at these paths on Bank 2:
1. O2S subharness (O2S signal, ground, and heater)
(check for pinched or broken wires; remove PCM and ohm out the O2S wires at the PCM harness connector);
2. Upstream of O2S
(air leak = lean O2S voltage = postive LTFTs,
injector leak = rich O2S voltage = negative LTFTs);

You may need to log these:
RPM, TPS, MAF, MAP, AFR, FTC, LTFT, STFT, IAT, ECT, SPARK, KR, HO2S11, HO2S21
Misfire Counts (Current) for all cylinders;

display these as a chart and post an image on this thread.