Vacuum Leak '89 200Q

[larry C leung]

Been trying to find this for awhile, need ideas on where exactly to look,
as the propane trick isn't working.

Symptoms:

- No Codes, though chipped ECU, wouldn't mind a spare stock MAC-14 for
Diagnosis if availible....

- fails the dipstick test, though not all of the time.

- When cold (cool, oil up to temp) it runs fairly well, only an
occasional stumble.

- If running for over 20 minutes to 1/2 hour or more, you can step on the
throttle, boost builds on the gauge, and not much else happens but a
slight stumble. If you back off the gas and step in it again, it will
accelerate, though not in proportion to the boost.

- With propane, I checked the valve cover gasket, vacuum lines running
along the right side of the car (US passenger side), MM-hose,
intercooler, crankcase breather and ISV hoses. Valve cover gasket is new,
as is MM-hose. Intercooler is strapped.

- I tried (for diagnosis, will be replacing shortly) wrapping the
crankcase breather and ISV hoses in duct tape. Didn't help thought it did
help in the dipstick test.

It seems somewhat temperature related, obviously, as it does run better
cool.

Need help or suggestions as to where to look for the leak. I will check
the MM hose more carefully and the IC for oil leaks, though they were
okay when I last checked about 2 weeks ago.

Is it possible that it's the lower IC hose?

I'd love some help!

TIA, and hope you had a great T'giving if you were celebrating!

LL - NY