chevy47390

Hello,


I found an interesting article in Motor Magazine August 2008.
This partial text relates specifically to our Ventures.
The defect described is exactly that observed on mine.

can someone explain to me what it was called precisely " purge Hose" and where is it located.
This operation to confirm a failure of O2 sensor.

and about replacing the oxygen sensor, it is mentioned only one lambda probe, while Venture have two Oxygen Sensor. one after exhaust manifold and the second after the catalytic converter.
Which is to replace first?

Thank you for your answers.

the text :
<<<<<<here's a="" concrete="" example="" to="" illustrate="" what="" i="" mean.="" the="" vehicle="" in="" question="" is="" 1999="" chevy="" venture="" minivan="" with="" 3.4l="" v6.="" there="" was="" dtc="" p0171="" (exhaust="" too="" lean,="" bank="" 1)="" memory="" an="" active="" mil.="" sum="" of="" short="" term="" and="" long="" fuel="" trims="" freeze="" frame="" excess="" 50%.="" pressure="" volume="" had="" been="" verified="" as="" within="" specification.="" when="" evaluating="" trim="" trouble="" code,="" one="" first="" steps="" must="" always="" be="" verify="" that="" oxygen="" sensor="" (on="" which="" based)="" functioning="" correctly.="" during="" test="" drive,="" observed="" o2="" switching="" rich,="" but="" not="" often="" would="" expected="" if="" very="" large="" corrections="" shown="" were="" actually="" effective.="" indeed,="" on="" face="" it,="" datastream="" seemed="" confirm="" dtc.="" longtime="" readers,="" however,="" can="" probably="" anticipate="" my="" next="" tests="" were:="" checked="" actual="" lambda="" value="" exhaust="" gases.="" then="" looked="" for="" dynamic="" response="" artificially="" enriched="" system="" blast="" propane,="" enleaned="" it="" by="" disconnecting="" major="" vacuum="" hose.="" (see="" "what="" goes="" in�harnessing="" diagnostic="" tool"="" september="" 2005="" issue="" motor.="" search="" index="" at="" <a="" href="http://www.motormagazine.com" target="_blank">MOTOR Magazine | MOTOR Information Systems for all Motor magazine articles mentioned.) Having found the idle lambda at a ridiculously low value of .85 (indicating a mixture with 15% more fuel than needed), I was not surprised to see that the O2 sensor didn't register a rich condition until the engine was very nearly flooded with propane. When I removed the purge hose, engine rpm climbed and the engine smoothed out, while lambda marched toward the stoichiometric ideal value of 1.00. Once the faulty O2 sensor was replaced, all aspects of driveability improved, and the minivan returned to its previous fuel consumption levels.>>>>>></here's>

chevy47390

for visitors:

the purge hose comes from the canister :
This is the EVAP system that retrieves gasoline vapors in the tank.

The purge hose is accessible in the engine compartment near the arrival and return fuel lines and is disconnectable at this point, he has a jack to check the pressure. This jack bears a label.

WE can disconnect the purge hose at this point and there are no DTC. It seems complicated and it takes exceptional conditions for gasoline to go up by this hose and thus flooding the engine. the O2 sensor detects the congestion and there is no reaction PCM. (?)

We know more about this system, but it was not the right track search

chevy47390

for visitors:

the purge hose comes from the canister :
This is the EVAP system that retrieves gasoline vapors in the tank.

The purge hose is accessible in the engine compartment near the arrival and return fuel lines and is disconnectable at this point, he has a jack to check the pressure. This jack bears a label.

We can disconnect the purge hose at this point and there are no DTC. It seems complicated and it takes exceptional conditions for gasoline to go up by this hose and thus flooding the engine. the O2 sensor detects the congestion and there is no reaction PCM. (?)

We know more about this system, but it was not the right track search

tech2

the article is describing how the tech tested the operation of the front oxygen sensor(before the cat). first he en-richened the mixture by adding propane into the incoming air stream. then he leaned the mixture out by removing the purge line and creating a vacuum leak. The system ran better as the system was bias lean and this compensated for the rich mixture.

not seeing an adequate change in the response from the o2 sensor when forcing it rich and them lean; he knew the sensor was bad.

chevy47390

Thank you, Tech2, for correcting me.

I was greatly misled me in my analysis of the text of Motor magazine. I was caught in my quest to figure out why my engine had this rough idle and was reluctant to effort. When I created the discussion, the EVAP system was not excluded.
I understand better why they talk about propane.
but I do not understand the whole substance of the article.
I'm not yet to check an known bad O2Sensor !

tech2

an bad o2 sensor is not likely the cause to a rough idle.