EVAP & transmission problems related?

[cz]

Vehicle Specs:
2000 Saturn SL2 with just over 14,000 miles

Background:
Since October my 'Service Engine Soon' light has been coming on with
some degree of frequency. My service technicians say the problem is
in the EVAP system. Initially I was told to turn my gas cap at least
three clicks after pumping gas. When that didn't work, the gas cap
was replaced. When that didn't work, some temperature related element
(a thermostat if memory serves correctly) was replaced. I think there
was one other replacement after that. Things seemed to be going
better (as measured by almost a month without a 'Service Engine Soon'
light coming on) until a month and a half ago when my transmission
(rear & 2nd gear to be specific) blew and I had to have it replaced.
This morning the 'Service Engine Soon' light popped on and sure
enough, the technicians are telling me that it's the EVAP system
again. At this point they say they have run every test known and
consulted with Saturn engineers. They ultimately replaced one of the
two solenoids, simply because the only parts of the EVAP system that
haven't been replaced are the solenoids, so they're hoping this fixes
it, and if it doesn't, then they'll simply fix the other solenoid.

Question:
Since I've never personally known someone with either EVAP problems or
a blown transmission, and since most of the people I know are driving
cars older than mine and those cars have had significantly less engine
problems than mine, I can't help but wonder - is it possible that my
transmission blew because of the mystery EVAP problem/s?

 

[Bob Shuman]

In my opinion, the answer to your question is "No" ... it is not likely the
two are related.

Bob

 

[Oppie]

My experience with a '01 lw300 having an evap code was that the vent
solenoid was not closing properly. The valve is normally open when the
engine is off and closes to allow the purge solenoid to clear vapors from
the canister. I replaced the vent solenoid three times, the first two being
at one year intervals. The last replacement has been in place for almost
three years now.
The Evap system test, which is preformed regularly by the onboard
computer, closes the vent solenoid, opens the purge solenoid and monitors
the vacuum in the tank. At some point, the purge is closed and the vacuum
sensor monitors the pressure in the tank. Depending whether it holds at
level, falls slowly or falls fast, it gives either a normal, slow leak or
gross leak code respectively. My car kept throwing the gross leak code which
was equivalent to a loose gas cap.

Many of the codes that cause a MIL light to come on will cause the engine to
run in open loop. This in turn messes up the finely tuned relation between
engine management and transmission control. In short, the engine may seem to
run fine but transmission shifts like crap.

Hope my little dissertation was useful - Oppie

 

[cz]

My experience with a '01 lw300 having an evap code was that the vent
solenoid was not closing properly. The valve is normally open when the
engine is off and closes to allow the purge solenoid to clear vapors from
the canister. I replaced the vent solenoid three times, the first two being
at one year intervals. The last replacement has been in place for almost
three years now.
The Evap system test, which is preformed regularly by the onboard
computer, closes the vent solenoid, opens the purge solenoid and monitors
the vacuum in the tank. At some point, the purge is closed and the vacuum
sensor monitors the pressure in the tank. Depending whether it holds at
level, falls slowly or falls fast, it gives either a normal, slow leak or
gross leak code respectively. My car kept throwing the gross leak code which
was equivalent to a loose gas cap.

Many of the codes that cause a MIL light to come on will cause the engine to
run in open loop. This in turn messes up the finely tuned relation between
engine management and transmission control. In short, the engine may seem to
run fine but transmission shifts like crap.

Hope my little dissertation was useful - Oppie

Oppie,

I was actually following your explanation until "This in turn messes
up the finely tuned relation between engine management and
transmission control." Does this mean that an 'engine running an open
loop' could cause transmission failure?

 

[Oppie]

Oppie,

I was actually following your explanation until "This in turn messes
up the finely tuned relation between engine management and
transmission control." Does this mean that an 'engine running an open
loop' could cause transmission failure?

I meant to say that there is a finely tuned relationship between an engine
running in closed loop and the transmission/powertrain controller. When the
engine is running in open loop, This tuning is ignored and all reverts to
limp home mode.

I can't speak for all systems, but when I have gotten engine codes, the
traction control light (on the TRAC button) turns off and the transmission
shifts very hard. I would expect that if that type of shifting should
continue for a long enough period, it may cause a failure in the
transmission.

I had to laugh when I read your description of their troubleshooting. It
shows a minimal understanding (if that) of the diagnostic systems. The bit I
wrote was almost verbatim (albeit from memory) from the factory service
manual. Any tech with access to a tech II or equivalent should be able to
read the canister vacuum sensor value and make a reasonable determination.
For that matter, putting a gauge on the test port can do almost the same
thing to monitor when a evap canister test is invoked.

Oppie

 

[-Cronus-]

Transaxle people... TransAXLE...
14k miles?
I cant follow this post... Without providing codes a verifiable
diagnosis for these problems would be futile. In the future write this
stuff down and get second opinions while the issues are occurring.