vt o2 sensor problem!!!! HELP!!!!!

[mickymodge4]

hi there ok i have a car vt v6 on gas runs fine on gas (wot the) on petrol drives ok but idles like a pig!!! came in with fuel injectors stuffed so wacked in a reco set improved driveabiliuty but idles still no good. checked fuel press, pressure regulator, vacuum leaks reset and cleaned iac and t/b. Checked codes found 76 shrt term fuel trim prob and rich exhaust so wacked in a couple of o2 sensors and still no change at all!!! i even checkd to see if the o2 sensors were cycling and the scan tool showed them one stuck on 970 nv the other was on like 200 mv!!!!! and they are new???? its like the ecu isnt reading the signal from the 02 sensors and they are new!!!! could the gas wiring have stuffed up the signals to the ecu????

[moose man]

Don't forget that the O2 sensor is just that - a sensor. It will only sense what is in front of it. They are sensing a problem somewhere else in the engine.
Keep looking for reasons that one cylinder bank would be rich and the other lean. Misfire? intake or exhaust manifold air leak? burnt valve?
What is long term fuel trim value?

Need more info.

[mickymodge4]

yepi forgot that i check for misfires and all ok replaced plugs as it didnt have gas plugs in it the leads look new cant test them as they are the 'revised type" but under load it doesnt miss a beat. checked vacuum hoses for leaks esp near throttle body where they always pop off and back of manifold did fing all manifold bolts loose as so tightened all but still no difference ant sprayed crc round manifold and nothing. checked exhaust for cracks leaks etc and still no luck i even checked the cat conv visually and looks fine!!! didnt get fuel trim long term values as the scan tool i used i went into ultratune and they checked o2 sensors that was all didnt check fuel trims..any other ideas??

[mickymodge4]

oh also i did compression tests this was one of the first checks i did as i thought it may be a burnt valve and all came up good cant remember exact values but there was hardly any variation between cylinders...if it was a burnt valve wouldnt it run like crap on gas too???

[showbags]

check for leak between maf sensor and throttle body.

[mickymodge4]

yes i just rechecked for vacuum leaks first checkd with a piece of hose to ear no go then checked with a whole can of wd 40 and practically sprayed it on every seam where there could be airflow!!!!!! this car is killing me!!!!

[codeunknown]

air mass sensor !

it prob having issues with mapping the air and telling the injectors ...for leaded or unleaded...

[mickymodge4]

hahahaha tried that too got one from wreckers to swap over and didnt change at all!!! really stumped me this one...

[moose man]

have you checked the ribbed concertina tube between the air flow sensor and the throttle body? LPG systems pop them between the rubber folds and they can be difficult to find. I still don't think it's this though. One bank is rich and the other lean.

Exactly what codes come up?

You need to start testing each sensor with a multimeter or scoping tool to see if it's operating within parameters.
Also, don't keep swapping second-hand bits in and out unless you know they're 100%. This mostly proves to be a waste of money for most people.

One important question though. How did you know the injectors were stuffed? Was this code coming up before you replaced the injectors?

[mickymodge4]

hey mooseman yep checked the ribbed concertina on the intake and all ok..yes the left bank plugs seem to be more fuelly than the rhs.. by memory (im at my other workplace now) i think code 65 short term fuel trim problem??? or 67 rich exhaust....i have tested all sensors just checked the tps and the haynes manual ive got is incorrect!!!! has to be ive checked the range of volts from closed thrott to wot and it ranged fron .5 volts to 4.5 and this was even the case on a brand new sensor...in the book its says it should range from 4.5 v to 5volts!!!! have also checked params for iac as well and ok. ummm with the injectors i checked fuel press and regulator first all ok... then i took off inj leads one at a time and found a suspect one and when the guy cleaned them he found one spray pattern us and the car was only run on gas for a long time before i got it

[delcowizzid]

yeas the book is wrong 0.5 to 4.5/5 is fine.

[mickymodge4]

thought i was going crazy thanks delco wizz oh one thing i did find which improved the idle was inside the intake tube found one or those vortect fuel saver things!!!! installed after the airflow meter which was buggering up the air flow readings the engine was MEANT to be getting!!!! took it out made a considerable difference however still not idling how a vt should...ive noticed it does it more when warm and while driving it the problem will occur between closed throttle and progression ie taking of at lights or just increasing throttle from a low speed intermittently...also my inst fuel reading shoots up all over the place like up to 72 lt/hr and then back down!!! and driving the car only 25 mins today the dist to empty has gone from 300 to 200!!!!

[bricat]

What about disconnect battery to re-set computer? Just a thought.

[mickymodge4]

yep tried tried disconnecting battery hehe

[mickymodge4]

PROBLEM SOLVED!!!!! after so many sleepless nights ive solved the problem...burnt out exhaust valve on number 3 cylinder... what was throwing me off was two factors both compression tests i did came back within specifications 185-200 psi in each cylinder. decided to do a leak down test before rippin apart the heads (wanted to be 100% certain) found cylinder 3 leaking air whem pumped up...could hear hissing coming from near spark plug hole thus removed ex manifold to hear escaping air gettn past the exhaust valve sprayed soapy water down the exhaust port and BINGO!!!!! why wasnt this leak being picked up on my compression test??? esp when on comp tests the pressure was up at 200 psi and on the leak down test it was only at 120 psi on my guage???? also why didnt this play up on gas as well??? coz gas dont burn as hard????