EVAP & transmission problems related?

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?

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

Bob

Reply to
Bob Shuman

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

Reply to
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?

Reply to
cz

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

Reply to
Oppie

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.

Reply to
-Cronus-

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