My 94 T-5 suffers from the same smell and I have swapped between different high octane fuels and can not get rid of this smell, however I do not notice this on start up either in cold or warm just when the car has been running for a while specially if I give the turbo a squirt between traffic lights and then pull up, I have asked many people about this and know one can explain it.

Gary

If you only get this a for few minutes after a cold start it's due to the catalityc converter, it smells for a few minutes and disapears once the converter as reached its operating temperature (It took a while to convince my spouse that I had nothing to do with it... ;) The reason you get this at red light or stops is that the putrid exhaust fumes get sucked back into the car through the window or the ventilation.

I was told by the mecanic that changing the converter or blaming it on the dog were the only two options, since I only get it cold mornings and it only lasts for a few minutes on my 94 GLT, I chose to wait till the exhaust system was ready to go before undertaking the change.

If you need a confirmation, start the car on a cold day then go out of the car and weait for the smell. If you it outside then it's not the ventilation.

Just a note on the gas cap. It doesn't vent. It's supposed to seal and if it actually does fail and vent the tank the ECU can turn on the check engine light.

About the smell, I'd try a different brand of gas, a fuel system cleaner, make sure your air filter isn't clogged. Wouldn't hurt to do a tune-up if it's been a while. At 108k, a distributor cap, rotor, plugs, flame trap, etc wouldn't be a bad idea.

If all that fails you could have the cat tested for back pressure. Could be clogged or otherwise defective.

Have you checked for any fault codes?
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Erwin in Memphis, '95 855t

I was doing some research today on octane, and learned a few things that can cause this. One is use of the wrong octane. Too high an octane, for instance, can flood the catalytic converter with unconverted fuel. The overflow escapes the tailpipe (and fills up our nostrils.) Sometimes the manufacturer's fuel composition can create this problem - try switching brands. Your car is rated for 87 (no turbo) so it does you no benefit to buy the higher octane formulation.

(Higher octane does NOT provide more power or run cleaner than other grades; it's formulated with a higher-temperature flashpoint for turbocharged, variable intake, and high rpm engines).
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(98 S70 T5SE misc mods, mostly lighting) (92 940GLE)

I would do the 91 octane thing, and maybe add a can of BG44K once. I remember a Ponyiac I had smelled like rotten eggs most of the time. Have you tuned it recently? May be time.