8.1vortec

[RWA]

i have a 2002 yukon XL w/8.1 motor w/ 52k. recently had the torque converter replaced under warranty. since then mileage is down by about 100 miles per tank around town. also power is noticably down from normal. seems to have lost that torquey snap. somthing i noticed is that at low rpm 1800-2400 1/4 to 1/2 throttle there is a sucking sound like a cold air intake(mine is stock) this noise is only made when tranny temp is warmed up. also much louder towing or under load. this sound is new. no check engine light. also when towing my 8000# toybox I'm only getting 5.5 miles per gallon, down by 3mpg. anyone have any Ideas what is wrong?

Thank you

[ChevyTech007]

I may be off base but my first thought is a clogged catalytic converter. I would have an exhaust back pressure test done.

[RWA]

I may be off base but my first thought is a clogged catalytic converter. I would have an exhaust back pressure test done.

 

<{POST_SNAPBACK}>

 

 

the service writer metioned that too which would make sense accept for the noise i mentioned, and why does the noise seem to start when tranny temp gets close to normal. but thank you for your input

[RWA]

took it in today and they said cats were good, with no codes. they did not do a back pressure test but did a voltage check on the O2 sensor, saying both sides were equal. he is now looking at the throttle body. there is a noise that sounds like air sucking from about 1700-2400rpm under partial throttle. it is not a gradual noise it comes on and off like a switch. it does get louder as load increases at the same rpm range. he does not understand the relationship if any to the decrease in mpg and loss of power.

anymore suggestions?

thanks

[RWA]

brought truck home on friday. the tech inspected and cleaned throttle body-ok he checked both cats backpressure- was very low well within spec. they thought the egr valve could have been making the air noise but it checked ok.the nature of the air noise - abruptly coming on through a narrow rpm range during 1/4-1/2 throttle then abruptly stopping. while the air noise is happening i can change the pitch of it by changing throttle position. during yhis time there is a slight loss of power especialy when towing. the power comes back after the noise stops.

 

any thoughts?

thanks

[KICK]

i have a 2002 yukon XL w/8.1 motor w/ 52k. recently had the torque converter replaced under warranty. since then mileage is down by about 100 miles per tank around town.

 

<{POST_SNAPBACK}>

 

 

 

 

if the sucker ran fine until you had the torque converter replaced, and the problem started when the new torque converter was installed, it would lead one to think that they could have installed the wrong or a defective( bad stator??) torque converter.

 

stranger things have been know to happen.

[rockertype]

I hate to sound like a know it all but c'mon man! The torque converter is junk! JEEEZZZ!!