Thanks i really appreciate your help on this i will get back with some numbers here asap , now woth regard to a faulty o2 sensor , i did disconnect them all somas to run in open loop and their was no change , or maybe thats not the right way to go about it or does this also rule out an o2 sensor ?

hopefully i will have more info after the weekend , weather looks nasty .

 

When you unplug the O2 sensors the truck goes back to open loop and fuel is controlled by the other relevant sensors - MAF, MAP, ECT, TPS, ... In this scenario fuel trims have no meaning but if the truck runs the same under a load then yes that reduces the likelyhood of this being an O2 sensor problem but does not eliminate that possibility if the PCM did not like the input in the first place. Do both banks go into closed loop and stay closed after the truck warms up?


George

 

Yes both banks go into closed loop and stay closed .

 

This also happens at the same time the p0300 issues but i have changed the maf with no improvement . notice that bank 1 in this scenario is lean and bank2 is barely rich complete opposite , ecm maybe ?

 

That MAF sensor code brings up other possibilities.

Check the air intake from filter to throttle body looking for leaks. Replace the or filter is due. Check the quality of the power and ground to the sensor. We may need to check the quality of the sensor wire from the sensor to the ECM.

Another issue is now in play, excessive back pressure in the exhaust. You can either measure back pressure at an O2 sensor port or pull a sensor and go for a test ride.

Lastly we better check all the other sensors in live data to make sure that they make sense. ECT, TPS, MAP/BARO, IAT.

Sure the ECM is always a possibility but that is not the most likely.

 

Wonder if one (or both) of the front most O2 sensor(s) are pulled..and then drive with one or both out, if it will be better? Cat thought....

 

If your acceleration improves with O2 sensors removed you may have excessive back pressure. It’s a shade tree mechanic hack that can help diagnose. The best test is a back pressure gauge. There are also some vacuum gauge diagnosis.

George

 

almost forgo this post was alive , anyway ive removed the cat and resonator and now exhaust is free , though it runs better i havent had time to deal with this one as it drives fine except up mountainous hills which isnt a problem really for me , i will be back to finish thios one after my other 2 are complete \, i bought a 2001 and a 96 for cheap boteh with issues and mainteance needs of course but we are getting through that , the usual gas tank , brake line leaks atec etc .soo you soon