This is a weird one... engine or transfer case issue 02 envoy 4.2 ~200k

shovenose

Original poster
Member
Apr 24, 2016
318
SF Bay Area, CA
somewhere between 190k-200k don't remember exact mileage (odometer changed with different mileage one and i forgot what the difference was)

first time driving the envoy since my boyfriend has been using it as a daily driver. i was in a parking lot, put it into reverse to back into a parking spot and it was acting really weird. like almost stalling out - if i hadn't revved the engine it would have died.

it kind of does have a hesitation off idle but it's always done that as long as i've owned it. it's maybe stalled once or twice in the past year, usually when switching between reverse/drive.

i would think that it's a dirty throttle body - but it's not, because less than a year ago it was very thoroughly cleaned when we did the valve cover gaskets.

the reason i'm wondering if it has something to do with the transfer case, is because i noticed at the time it was doing it the auto light was blinking - weird, since the dial was (like always) in 2hi - we never use 4x4 or even automatic 4x4 as i know that one is not good for the transfer case. anyway, i switched the dial from 2hi to auto and back to 2hi and it went back to solid on 2hi.

i just got a fancy bosch scantool that can read all the different modules - this morning i connected it to the envoy for the first time just to see how well it worked, and had a whole bunch of codes in different modules (no check engine light though). i decided to delete them all and figured next time i see him and the envoy i'd scan again to see which ones came back.

so, i'll check them again when i get back to the house, and see if i can find anything relevant, but does anybody have any ideas?
 

Mike534x

Member
Apr 9, 2012
894
Has the Variable Valve Timing sensor or CPS ever been replaced? those usually cause stalling like symptoms when they go bad. When the CPS on my Envoy failed, it would cause the truck to shut off if I came to stop while it was in gear, it didn't happen all the time, but after doing a quick search on the forum and replacing it the same day it never happened again.
 

shovenose

Original poster
Member
Apr 24, 2016
318
SF Bay Area, CA
yeah put dorman in there about the same time as doing the valve cover gaskets. i know dorman's electrical stuff is garbage but it was the only option at local auto parts store at the time, and the old one had oil in the connector, was causing a cam/crank correlation code, and causing reduced engine power and service engine soon lights at the time. think it's already bad? wouldn't be too hard to replace it with an acdelco within the next few months. thing is it runs wonderfully otherwise which is why i think that thing is ok.
 

Mooseman

Moderator
Dec 4, 2011
25,262
Ottawa, ON
The CPAS can be bad and seem to run fine. It's a good place to start. And might as well clean the TB at the same time. When were the plugs done, if ever?

For the TC, it could be a number of things. The switch, the module, the encoder motor. For the module, if it's the original, it had a known failure issue. Mine would act up when it got cold. 2003+ modules were better.
 

shovenose

Original poster
Member
Apr 24, 2016
318
SF Bay Area, CA
The CPAS can be bad and seem to run fine. It's a good place to start. And might as well clean the TB at the same time. When were the plugs done, if ever?

For the TC, it could be a number of things. The switch, the module, the encoder motor. For the module, if it's the original, it had a known failure issue. Mine would act up when it got cold. 2003+ modules were better.

ok well i will put in an acdelco cpas next time we change the oil.

throttle body cleaned and new acdelco plugs installed less than a year ago when we did valve cover gaskets.

what part do i need from an 03+ envoy? i will change it if it's not too expensive.
 

Sparky

Member
Dec 4, 2011
12,927
The TCCM (transfer case control module).

I have one from a 2005 that I had put in my 2002 when my original died. Could sell it to you probably if you want it since my TB is now gone.
 

shovenose

Original poster
Member
Apr 24, 2016
318
SF Bay Area, CA
The TCCM (transfer case control module).

I have one from a 2005 that I had put in my 2002 when my original died. Could sell it to you probably if you want it since my TB is now gone.
please private message me. would rather give you the $ than ebay or picknpull
 

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